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Analytica Chimica Acta - Verlag: Elsevier
Analytica Chimica Acta bietet ein Forum für die zeitnahe Veröffentlichung von Originalarbeiten sowie kritische Bewertungen zu allen Apekten der Grundlagenforschung und der angewandten modernen analytischen Wissenschaft.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 9 February 2012 A. Jiménez Girón, K. Deventer, K. Roels, P. Van Eenoo A new doping control screening method for the analysis of diuretics and stimulants using ultra high pressure liquid chromatography-high resolution Orbitrap mass spectrometry has been developed. The screening was performed in full scan MS with scan-to-scan polarity switching which allowed to detect more than 120 target analytes. Sample preparation was limited to 10-fold dilution of the urine into the internal standard solution followed by injection. Total run time per sample was 10 minutes. Validation of the method yielded detection limits for diuretics between 25 and 250 ng mLand for stimulants between 5 and 500 ng mL. The screening method has been implemented in routine doping control.
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? A new doping control screening method using UHPLC-HRMS is presented ? Screening was performed in full scan MS with scan-to-scan polarity switching within a single run ? Sample preparation was minimized by a direct 10-fold dilution of the urine ? Detection limits were compliant with the imposed MRPLs by WADA
Publication year: 2012 Source: Analytica Chimica Acta, Available online 8 February 2012 Yating Xia, Min Cheng, Feng Guo, Xiangfang Wang, Jing Cheng An in-syringe demulsified dispersive liquid-liquid microextraction (ISD-DLLME) technique was developed using low-density extraction solvents for the highly sensitive determination of the three trace fungicides (azoxystrobin, diethofencarb and pyrimethanil) in water samples by high performance liquid chromatography-mass spectrometry chromatography–diode array detector/electrospray ionisation mass spectrometry. levelsME) al slsified dispersive liquid-liquid microemulsion In the proposed technique, a 5-mL syringe was used as an extraction, separation and preconcentration container. The emulsion was obtained after the mixture of toluene (extraction solvent) and methanol (dispersive solvent) was injected into the aqueous bulk of the syringe. The obtained emulsion cleared into two phases without centrifugation, when an aliquot of methanol was introduced as a demulsifier. The separated floating organic extraction solvent was impelled and collected into a pipette tip fitted to the tip of the syringe. Under the optimal conditions, the enrichment factors for azoxystrobin, diethofencarb and pyrimethanil were 239, 200, 195, respectively. The limits of detection, calculated as three times the signal-to-noise ratio (S/N), were 0.026 ?g·Lfor azoxystrobin, 0.071 ?g·Lfor diethofencarb and 0.040 ?g·Lfor pyrimethanil. The repeatability study was carried out by extracting the spiked water samples at concentration levels of 0.02 ?g mLfor all the three fungicides. The relative standard deviations varied between 4.9 and 8.2% (n = 5). The recoveries of all the three fungicides from tap, lake and rain water samples at spiking levels of 0.2, 1, 5 ?g Lwere in the range of 90.0-105.0%, 86.0-114.0% and 88.6-110.0%, respectively. The proposed ISD-DLLME technique was demonstrated to be simple, practical and efficient for the determination of different kinds of fungicide residues in real water samples.
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? The pretreatment apparatus is the first introduced. ? The pipette tip is a efficient preconcentration tool. ? The LOQ of the proposed technique is very low
Publication year: 2012 Source: Analytica Chimica Acta, Available online 7 February 2012 Miriam Sanz, Brígida Fernández de Simón, Enrique Esteruelas, Ángel Mª Muñoz, Estrella Cadahía, ... Polyphenolic composition of two Syrah wines aged during six or twelve months in medium toasting acacia and oak 225 L barrels was studied by LC-DAD-ESI/MS. A total of 43 nonanthocyanic phenolic compounds were foundin all wines, and other 15 compoundsonly in the wines from acacia barrels.Thus, the nonanthocyanic phenolic profile could be a useful tool to identify the wines aged in acacia barrels. Among all of themthe dihydrorobinetinhighlights because of its high levels, but also robinetin, 2,4-dihydroxybenzaldehyde, a tetrahydroxydihydroflavonol, fustin, butin, a trihydroxymethoxydihydroflavonol and 2,4-dihydroxybenzoic acid were detected at appreciable levels inwines during aging in acacia barrels, and could be used as phenolic markers for authenticity purposes. Although longer contact time with acacia wood mean higher concentrations of phenolic markers found in wines, the identification of these wines will also be easy after short aging times due the high levels reached by these compounds,even after only two months of aging.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 6 February 2012 Yu Kyung Tak, Won Young Kim, Min Jung Kim, Eunyoung Han, Myun Soo Han, ... Forensic DNA samples can degrade easily due to exposure to light and moisture at the crime scene. In addition, the amount of DNA acquired at a criminal site is inherently limited. This limited amount of human DNA has to be quantified accurately after the process of DNA extraction. The accurately quantified extracted genomic DNA is then used as a DNA template in polymerase chain reaction (PCR) amplification for short tandem repeat (STR) human identification. Accordingly, highly sensitive and human-specific quantification of forensic DNA samples is an essential issue in forensic study. In this work, a quantum dot (Qdot)-labeledAlusequence was developed as a probe to simultaneously satisfy both the high sensitivity and human genome selectivity for quantification of forensic DNA samples. This probe provided PCR-free determination of human genomic DNA and had a 2.5-femtogram detection limit due to the strong emission and photostability of the Qdot. The Qdot-labeledAlusequence has been used successfully to assess 18 different forensic DNA samples for STR human identification.
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? Genomic DNA quantification were performed using a quantum dot-labeledAlusequence ? This probe provided PCR-free determination of human genomic DNA ? Qdot-labeledAluprobe-hybridized genomic DNAs had a 2.5-femtogram detection limit ? Qdot-labeledAlusequence was used to assess DNA samples for human identification
Publication year: 2012 Source: Analytica Chimica Acta, Available online 7 February 2012 R.Cela, R. Phan-Tan-Luu, M. Claeys.Bruno, M. Sergent Optimal fractions of resolution V design matrices proposed by Rechtschaffner in 1967 are developed and applied as supersaturated designs in screening experiments. Rechtschaffner matrices allow evaluation of all main factors and two-factor interactions, which in many real-world studies are of practical significance. However, the number of experimental runs increases rapidly with the number of factors in the matrices, which are therefore impractical for more than 5-6 factors. On the contrary, saturated fractions based on Hadamard matrices, which are commonly applied in screening studies, cannot evaluate the interaction effects. Here, a procedure for selecting the optimum fractions of Rechtschaffner matrices is presented and provides supersaturated matrices that are well adapted to a variety of problems, thus allowing the development of screening studies with a relatively small number of experiments. The procedures developed to derive the size-reduced matrices and to evaluate the active factors are discussed and compared in terms of efficiency and reliability, by means of simulation studies and application to a real problem. These fractions are the first supersaturated design matrices capable of estimating interaction effects. Additionally, one important advantage of these supersaturated matrices is that they enable development of follow-up procedures in cases of inconclusive results, by enlarging the matrix and eventually resolving the full Rechtschaffner matrix of departure when it is necessary to evaluate the active factors and their interactions.
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? The first supersaturated matrices allowing the estimation of main effects and two-factor interactions are presented ? An efficient procedure for the construction of optimal fractions of Rechtschaffner matrices is proposed ? Efficient and practical procedures for the resolution of these supersaturated matrices are developed ? The usefulness of these matrices is demonstrated in simulation experiments as well as using literature real life data
Publication year: 2012 Source: Analytica Chimica Acta, Available online 6 February 2012 Veronica Obuseng, Florence Nareetsile, Habauka M. Kwaambwa Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using theMoringa oleiferaseeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II) > Cu(II) > Cd(II) > Ni(II) > Mn(II) and Zn(II) > Cu(II) > Ni(II). The general trend of the heavy metals ions uptake by the amine-based ligand followed decreased in the order Mn > Cd > Cu > Ni > Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5 to 8.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 6 February 2012 C. Tistaert, B. Dejaegher, G. Chataigné, C. Rivière, M. Chau Van, ... SomeMallotusspecies are commonly used traditional medicine (TM) ingredients in Vietnam and China, but only a few are studied for their activities. In Part I, High-Performance Liquid Chromatography (HPLC) fingerprints of 39Mallotussamples (17 species) were developed and, because of the complexity of and the large differences between the samples, it was chosen to analyse the unaligned fingerprints. The peaks, potentially responsible for the antioxidant activity in givenMallotusspecies, were indicated by the regression coefficients from an Orthogonal Projections to Latent Structures (O-PLS) model. In the present study, an in depth discussion on the need for alignment of theMallotusfingerprints for the indication of the potentially active compounds is made, as well as an experimental analysis and identification of the previously indicated peaks by HPLC-MS. Additionally, to thoroughly study and discuss the alignment problem, the modelling and prediction of the antioxidant activity of green tea samples based on HPLC fingerprints was also considered.
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? Indication of peaks responsible for the antioxidant activity ofMallotusspecies (O-PLS) ? Development of a warping strategy based on Correlation Optimized Warping ? Evaluation of a multivariate model prior and after alignment for indicative and predictive purposes ? LC-MS analyses of the indicated peaks
Publication year: 2012 Source: Analytica Chimica Acta, Available online 4 February 2012 Daiane de O. Dias, Mariana Colombo, Regina G. Kelmann, Tatiane P. De Souza, Valquiria L. Bassani, ... Recent studies have shown the anti-inflamatory activity of Copaiba oils may be addressed to the high content of ?-caryophyllene, the most common sesquiterpene detected, especially in theCopaifera multijugaHayne species. In the present study, nanoemulsions were proposed as a delivery system for copaiba oil in view to treat locally inflamed skin. This article describes the optimization and validation of a stability-indicating SPME-GC method, for ?-caryophyllene analysis in the nanoemulsions produced by high pressure homogenization. SPME extraction methods are performed with PDMS (polydimethylsiloxane) fiber (100 ?m). Three SPME parameters were evaluated by a three-level-three-factor Box–Behnken factorial design as potentially affecting the technique efficiency. According to the results obtained, the best conditions to extract ?-caryophyllene were: (i) sampling temperature of 45 °C, (ii) sampling time of 20 minutes and (iii) no NaCl addition. Results coming from the forced degradation tests showed a reduction of ?-caryophyllene peak area when both caryophyllene methanolic solution and nanoemulsions were exposed to acid hydrolysis, UV-A irradiation, oxidative (H2O2) and thermolitic (60 °C) conditions. Such reduction occurred in lower extent in the nanoemulsions, suggesting a protective effect of the formulation to ?-caryophyllene content. Since no degradation products were detected in the same retention time of ?-caryophyllene, the specificity of the method was demonstrated. The method was linear in the range of 0.14–0.68 ?g mLof ?-caryophyllene (r > 0.999), and was also validated for precision (R.S.D. ? 5.0%), accuracy (97.85% -101.87%) and robustness. Finally, the method was applied to quantification of ?-caryophyllene content in the developed formulations.
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? A SPME-CG method is proposed for ?-caryophyllene assay in nanoemulsions containing copaiba oil ? SPME parameters were optimized for efficient ?-caryophyllene extraction ? The stability-indicating capability and specificity of the method were satisfied ? Nanoemulsions partially protected ?-caryophyllene under stressing conditions ? The proposed method presents linearity, lows LOD and LOQ, good precision, accuracy and robustness.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 3 February 2012 Elefteria Psillakis, Evangelia Yiantzi, Lucia Sanchez-Prado, Nicolas Kalogerakis A new headspace solid-phase microextraction (HSSPME) procedure carried out under vacuum conditions is proposed here where sample volumes commonly used in HSSPME (9 mL) were introduced into pre-evacuated commercially available large sampling chambers (1000 mL) prior to HSSPME sampling. The proposed procedure ensured reproducible conditions for HSSPME and excluded the possibility of analyte losses. A theoretical model was formulated demonstrating for the first time the pressure dependence of HSSPME sampling procedure under non equilibrium conditions. Although reduced pressure conditions during HSSPME sampling are not expected to increase the amount of analytes extracted at equilibrium, they greatly increase extraction rates compared to HSSPME under atmospheric pressure due to the enhancement of evaporation rates in the presence of an air-evacuated headspace. The effect is larger for semivolatiles whose evaporation rates are controlled by mass transfer resistance in the thin gas film adjacent to the sample/headspace interface. Parameters that affect HSSPME extraction were investigated under both vacuum and atmospheric conditions and the experimental data obtained were used to discuss and verify the theory. The use of an excessively large headspace volume was also considered. The applicability of Vac-HSSPME was assessed using chlorophenols as model compounds yielding linearities better than 0.9915 and detection limits in the low-ppt level. The repeatability was found to vary from 3.1 to 8.6%.
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? Pressure dependence of HSSPME under non equilibrium sampling conditions. ? Faster extraction rates for HSSPME under vacuum conditions. ? Higher sensitivity within short sampling times and under mild conditions. ? Proposed procedure enables sampling of all compounds amenable to HSSPME.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 2 February 2012 Mojtaba Hadi, Ahmad Rouhollahi Nanocrystalline graphite-like pyrolytic carbon film (PCF) electrode fabricated by a non-catalytic chemical vapor deposition (CVD) process was used for the simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrode was studied with respect to changes in electrocatalytic activity caused by a simple and fast electrochemical pretreatment. The anodized electrode exhibited excellent performance compared to many chemically modified electrodes in terms of detection limit, linear dynamic range, and sensitivity.Differential pulse voltammetry (DPV) was used for the simultaneous determination of ternary mixtures of DA, AA, and UA. Under optimum conditions, the detection limits were 2.9?M for AA, 0.04?M for DA, and 0.03?M for UA with sensitivities of 0.078, 5.345, and 6.192 A M, respectively. The peak separation was 219mV between AA and DA and 150mV between DA and UA.No electrode fouling was observed and good reproducibility was obtained in all the experiments. The sensor was successfully applied for the assay of DA in an injectable drug and UA in human urine by using standard addition method.
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? The nanocrystalline pyrolytic carbon film electrode as an electrochemical biosensor. ? The sensor for simultaneous detection of ascorbic acid, dopamine, and uric acid. ? Electrochemical pretreatment enhances the sensitivity and resolution.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 2 February 2012 Yulan Rao, Margaret McCooeye, Zoltán Mester For the first time a liquid chromatography method with high resolution mass spectrometric detection has been developed for the simultaneous determination all key metabolites of thesulfur pathwayin yeast, including all thiolic (cysteine (Cys), homocysteine (HCys), glutathione (GSH), cysteinyl-glycine (Cys-Gly), ?-glutamyl-cysteine (Glu-Cys)) and non-thiolic compounds (methionine (Met), s-adenosyl-methionine (AdoMet), s-adenosyl-homocysteine (AdoHcy), and cystathionine (Cysta)). The developed assay also permits the speciation and selective determination of reduced, oxidized and protein bound fractions of all of the five thiols. Iodoacetic acid (IAA) was chosen as the derivatizing reagent. Thiols were extracted from sub-mg quantities of yeast using hot 75% ethanol. The detection limits were in the range of 1-12 nmol Lfor standard solution (high femotomole, absolute), except AdoMet (116 nmol L), which was unstable. In freshly harvested yeast, most of the thiols were in the reduced forms and low levels of protein-bound GSH and Glu-Cys were found. In a selenium enriched yeast, the thiols were mainly in the oxidized forms, and a significant amount of protein-bound Cys, HCys, GSH, Cys-Gly and Glu-Cys were found. The method was also applied to the metabolic study of the adaptive response ofSaccharomyces cerevisiaeto hydrogen peroxide, cadmium, and arsenite, and the change in concentration of thiols in thesulfur pathwaywas monitored over a period of four hours.
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? LCMS method for the determination of free, oxidized and protein bound thiols in yeast was developed ? In freshly harvested yeast, most of the thiols were in the reduced forms ? The stress response of yeast to H2O2, Cd and As was studied via changes in the thiol profiles.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 2 February 2012 María del Mar Castro López, M.C. Cela Pérez, María Sonia Dopico García, José Manuel López Vilariño, María Victoria González Rodríguez, ... Molecularly imprinted polymer (MIPs) for solid extraction and preconcentration of catechins have been successfully prepared by a thermal polymerization method using quercetin as template, 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as crosslinker. A solution mixture of acetone and acetonitrile was used as porogen. Systematic investigations of the influence of monomer, cross-linker, porogen, as well as polymerization conditions on the properties of the MIPs were carried out. The quercetin MIPs were evaluated according to their selective recognition properties for quercetin, structurally related compounds (catechin, epigallocatechin gallate and epicatechin) and a unrelated compound of similar molecular size (<alpha>-tocopherol). Good binding was observed for quercetin, catechin and epigallocatechin gallate with an optimized MIP in a solid phase extraction system. Adsorption and kinetic characteristics were evaluated for catechins which indicated that the synthesized polymer had high adsorption capacity and contained homogeneous binding sites. Chemical and morphological characterization of the MIP was investigated by FTIR, SEM and BET, which confirmed a high degree of polymerization. Finally, the MIP was successfully applied to the clean-up and preconcentration of catechins from several natural samples.
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? Specificity and selectivity MIPs developed for the catechins contained in extracts ? Inherent bleeding is avoided using quercetin as template ? Fast and high adsorption in a homogeneous surface onto the MIP is observed. ? External film diffusion step is the limiting step of the adsorption process. ? Adsorption could be described as strong hydrogen bonds comparable to chemisorption
Publication year: 2012 Source: Analytica Chimica Acta, Available online 2 February 2012 E. Fernandez-Ahumada, J.M. Roger, B. Palagos Evaluation of uncertainty affecting predictions is a major trend in analytical chemistry and chemometrics. Several approximate expressions and resampling methods have been proposed for the estimation of prediction uncertainty when using multivariate calibration. This article proposes a new expression for the variance of prediction, adapted to near infrared spectroscopy specificities and particularly to the spectral error structure, induced by the high colinearity of the variables. The proposed analytical expression enables a detailed evaluation of the different contributions and components of uncertainty affecting the model. An application to real data of feedstuff near infrared spectra related to protein content has shown its advantages.
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? A new expression for prediction uncertainty estimation in linear regressions is proposed. ? It is the first one adapted to particularities of near infrared spectra. ? It clearly splits the sources of uncertainty and manages different types of error. ? A test on NIR spectra of feed stuff shows its advantages. ? Estimated values of the expression are in accordance with those of a resampling method.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 2 February 2012 Jian Sun, Ying Zheng, Xiaojun Feng, Wei Du, Bi-Feng Liu The propagation of intercellular calcium signals provides a mechanism to coordinate cell population activity, which is essential for regulating cell behavior and organ development. However, existing analytical methods are difficult to realize localized chemical stimulation of a single cell among a population of cells that are in close contact with one another for studying the propagation of calcium wave. In this work, a microfluidic method is presented for the analysis of contact-dependent propagation of intercellular calcium wave induced by extracellular ATP using multiple laminar flows. Adjacent cells were seeded ?300 ?m downstream the intersection of a Y-shaped microchannel with negative pressure pulses. Consequently, the lateral diffusion distance of the chemical at cell locations was limited to ?26 ?m with a total flow rate of 20 ?L·min, which prevented the interference of diffusion-induced cellular responses. Localized stimulation of the target cell with ATP induced the propagation of intercellular calcium wave among the cell population. In addition, studies on the spread of intercellular calcium wave under octanol inhibition allowed us to characterize the gap junction mediated cell-cell communication. Thus, this novel device will provide a versatile platform for intercellular signal transduction studies and high throughput drug screening.
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? A microfluidic device was made for intercellular calcium signals (ICS) studies. ? Localized stimulation of ATP induced ICS in contacting cells by laminar flow. ? The role of gap junction in ICS was investigated using this device.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 2 February 2012 A. Sabatié-Gogova, J. Champion, S. Huclier, N. Michel, F. Pottier, ... Astatine is a rare radioelement belonging to the halogen group. Considering the trace amounts of astatine produced in cyclotrons, its chemistry cannot be evaluated by spectroscopic tools. Analytical tools, provided that they are coupled with a radioactive detection system, may be an alternative way to study its chemistry. In this research work, High Performance Anion Exchange Chromatography (HPAEC) coupled to a gamma detector (?) was used to evaluate astatine species under reducing conditions. Also, to strengthen the reliability of the experiments, a quantitative analysis using a reactive transport model has been done. The results confirm the existence of one species bearing one negative charge in the pH range 2 ? 7.5. With respect to the other halogens, its behavior indicates the existence of negative ion, astatide At. The methodology was successfully applied to the speciation of the astatine in human serum. Under fixed experimental conditions (pH 7.4 ? 7.5 and redox potential of 250 mV) astatine exists mainly as astatide Atand does not interact with the major serum components. Also, the method might be useful for thein vitrostability assessment ofAt-labelled molecules potentially applicable in nuclear medicine.
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? First identification of an astatine species under reducing conditions bearing one single negative charge, most probably At? Astatide identified in human serum ? Proposition of a method for assessing the stability ofAt-labelled biological molecules in nuclear medicine.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 31 January 2012 Zheng Han, Chensen Chi, Bing Bai, Gang Liu, Qinxiong Rao, ... In this study we propose a chromogenic platform for rapid analysis of organophosphate (OP) and carbamate (CM) insecticide residues, based on recombinantDrosophila melanogasteracetylcholinesterase (R-DmAChE) as enzyme and indoxyl acetate as substrate. The visible chromogenic strip had the advantages identical to those of commonly-used lateral flow assays (LFAs) with utmost simplicity in sample loading and result observation. After optimization, depending on the color intensity (CI) values, the well-established assay has the capabilities of both qualitative measurement via naked eyes and quantitative analysis by colorimetric reader with the desirable IC50values against the tested six insecticides (0.06 ?g mLof carbofuran, 0.28 ?g mLof methomyl, 0.03 ?g mLof dichlorvos, 31.6 ?g mLof methamidophos, 2.0 ?g mLof monocrotophos, 6.3 ?g mLof omethoate). Acceptable matrix effects and satisfactory detection performance were confirmed by in-parallel LC-MS/MS analysis in different vegetable varieties at various spiked levels of 10-10 ?g g. Overall, the testified suitability and applicability of this novel platform meet the requirements for practical use in food safety management and environmental monitoring, especially in the developing world.
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? A visible chromogenic platform for rapid analysis of OP and CM insecticide residues was developed. ? The assay has the capabilities of both qualitative measurement and quantitative analysis. ? The sensitivity, capabilities of resisting interferences and storage stability were desirable. ? Matrix effects were acceptable and detection performance was satisfactory in real application.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 1 February 2012 Mohammad Saraji, Bahman Farajmand A new method based on combination of solid- and liquid-phase microextraction was developed. For the first time, porous flower-like silica microstructures with nanometric layers were created on the surface of the stainless steel wire by a new facile hydrothermal process. The fiber, coated with a suitable organic solvent, was applied for microextraction of some organophosphorus pesticides from aqueous samples followed by gas chromatography-nitrogen phosphorous detection. Method detection limits were between 0.6 and 3 ng L. Relative standard deviations for intra- and inter-day precision were 4.4-7.3% and 5.1-7.8%, respectively. Fiber-to-fiber reproducibility for five prepared fibers was 6.3-8.4%. Tap and river water samples were analyzed for evaluation of the method in real sample analysis. Relative recoveries for spiked tap and river water samples were in the range of 94-101% and 89-97%, respectively. In addition, the method was compared with two commercial solid-phase microextraction (SPME) fibers, single drop microextraction (SDME) and liquid-phase microextraction (LPME). The present method showed higher extraction efficiency as compared with SDME, LPME and commercial SPME fibers.
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? In this work combination of liquid- and solid-phase microextraction was applied as a novel extraction method. ? Flower-like microporouse silica was created on the surface of a stainless steel wire. ? The silica layer was coated with an organic solvent with enough vapor pressure to be easily evaporated inside the GC injector. ? The organic solvent was used as a renewable extracting phase in SPME. ? The new extracting phase was compared with two commercial SPME fibers and SDME method.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 31 January 2012 Mara Mirasoli, Angela Buragina, Luisa Stella Dolci, Massimo Guardigli, Patrizia Simoni, ... Simple, rapid and highly sensitive assays, possibly allowing on-site analysis, are required in the security and forensic fields or to obtain early signs of environmental pollution. Several bioanalytical methods and biosensors based on portable devices have been developed for this purpose. Among them, Lateral Flow ImmunoAssays (LFIAs) offer the advantages of rapidity and ease of use and, thanks to the high specificity of antigen-antibody binding, allow greatly simplifying and reducing sample pre-analytical treatments. However, LFIAs usually employ colloidal gold or latex beads as labels and they rely on the formation of colored bands visible by the naked eye. With this assay format, only qualitative or semi-quantitative information can be obtained and low sensitivity is achieved. Recently, the use of enzyme-catalyzed chemiluminescence detection in LFIA has been proposed to overcome these problems. In this work, we describe the development of a quantitative CL-LFIA assay for the detection of 2,4,6-trinitrotoluene (TNT) in real samples. Thanks to the use of a portable imaging device for CL signal measurement based on a thermoelectrically-cooled CCD camera, the analysis could be performed directly on-field. A limit of detection of 0.2 ?g mLTNT was obtained, which is five times lower than that obtained with a previously described colloidal gold-based LFIA developed employing the same immunoreagents. The dynamic range of the assay extended up to 5 ?g mLTNT and recoveries ranging from 97% to 111% were obtained in the analysis of real samples (post blast residues obtained from controlled explosion).
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? A lateral flow immunoassay for TNT (2,4,6-trinitrotoluene) has been developed. ? Chemiluminescence detection allows quantitative TNT analysis. ? On-field analysis is possible by using a portable chemiluminescence imaging device.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 31 January 2012 Andrew J. Percy, Martial Rey, Kyle Burns, David C. Schriemer Assessing the functional outcome of protein interactions in structural terms is a goal of structural biology, however most techniques have a limited capacity for making structure-function determinations with both high resolution and high throughput. Mass spectrometry can be applied as a reader of protein chemistries in order to fill this void, and enable methodologies whereby protein structure-function determinations may be made on a proteome-wide level. Protein hydrogen/deuterium exchange (H/DX) offers a chemical labeling strategy suitable for tracking changes in “dynamic topography” and thus represents a powerful means of monitoring protein structure-function relationships. This review presents the exchange method in the context of interaction analysis. Applications involving interface detection, quantitation of binding, and conformational responses to ligation are discussed, and commentary on recent analytical developments is provided.
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? Protein chemistry generates mass shifts useful for structure-function studies ? H/DXsupports a powerful mass shift method for protein interaction analysis ? H/DX mass shifts are useful for determining binding data (Kd, off-rates) ? Improved H/DX-MS workflows can accommodatecomplex protein systems
Publication year: 2012 Source: Analytica Chimica Acta, Available online 31 January 2012 David S.M. Ribeiro, João A. Lopes, João L.M. Santos, João A.V. Prior Nowadays, the use of a drug to modify a person's behavior with criminal intentions has become a growing public concern. In fact, stealthy drink spiking with certain drugs can cause the incapacitation of a potential victim of assault and in extreme cases can even lead to death. Belonging to the group of drugs used to commit drug-facilitated crimes is glibenclamide, which not only exhibits high sedation secondary effects but when subject to an overdose intake can lead to intense hypoglycemic episodes that could end with death. Suicide attempts and homicides through overdose with glibenclamide have already been reported.In this work and for the first time, it was developed a new methodology for detection of glibenclamide in spiked liquid samples (teas) by fluorometry (?ex = 300 nm; ?em = 404 nm). The novel methodology was also implemented in a miniaturized and portable automatic flow system based in the concept of multipumping with an in-line pre-separation unit. The separation of the drug from the liquid samples was achieved through adsorptionof the drug into activated charcoal packed within a mini column followed by elution with a solution composed by ethanol, hydrochloric acid and the surfactant CTAB (70%, 1.0 mol L, 0.01 mol L, respectively). The results allowed to obtain a linear working range for glibenclamide concentrations of up to 50 mg L(r = 0.9999) and the detection limit was about 0.81 mg Lof glibenclamide.
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? HIGHLIGHTS ? Glibenclamide in spiked drinks was already used to commit Drug-Facilitated Crimes. ? The drug can be extracted through adsorption in activated charcoal. ? Eluent was developed for desortion of the drug and its fluorometric monitoring. ? Methodology implemented successfully in an automatic and miniaturized flow system. ? First work in the literature for the detection of glibenclamide in teas.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 1 February 2012 Guosong Lai, Lili Wang, Jie Wu, Huangxian Ju, Feng Yan A multiplexed electrochemical immunoassay method was developed for simultaneous ultrasensitive measurement of tumor markers based on electrochemical stripping analysis of silver nanoparticles (Ag NPs). The Ag NPs were deposited on a disposable immunosensor array with a reduction reaction catalyzed by nanogold labels. The immunosensor array was prepared by covalently immobilizing capture antibodies on chitosan modified screen-printed carbon electrodes. Through a sandwich-type immunoreaction, antibody-functionalized Au NPs were captured onto immunosensor surface to induce the silver deposition from a silver enhancer solution. The deposited Ag NPs could be directly measured by anodic stripping analysis in KCl solution. The catalytic deposition enhanced the analytical sensitivity for detection of protein markers. The interference of dissolved oxygen could be avoided as the detection was performed with positive stripping potential range. Using carcinoembryonic antigen and ?-fetoprotein as model analytes, the proposed multiplexed immunoassay method showed wide linear ranges of three orders of magnitude with the detection limits down to 3.5 and 3.9 pg mL, respectively. The localized silver deposition, as well as the stripping detection process, eliminated completely the electrochemical cross talk between adjacent immunosensors. The immunosensor array exhibited acceptable reproducibility, stability and accuracy, showing a promising potential in multianalyte determination for clinical application.
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? A multiplexed immunoassay is proposed by stripping analysis of deposited silver. ? The silver deposition enhancement greatly improves detection sensitivity. ? The proposed method avoids the interference of dissolved oxygen. ? This method eliminates the electrochemical cross talk between adjacent immunosensors.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 31 January 2012 Linda Ahonen, Pekka Keski-Rahkonen, Taija Saarelainen, Jenni Paviala, Raimo A. Ketola, ... The feasibility of a microfluidic-based liquid chromatography-electrospray ionization/mass spectrometric system (HPLC-Chip/ESI/MS) was studied and compared to a conventional narrow-bore liquid chromatography-electrospray ionization/mass spectrometric (LC-ESI/MS) system for the analysis of steroids. The limits of detection (LODs) for oxime derivatized steroids, expressed as concentrations, were slightly higher with the HPLC-Chip/MS system (50-300 pM) using an injection volume of 0.5 ?L than with the conventional LC-ESI/MS (10-150 pM) using an injection volume of 40 ?L. However, when the LODs are expressed as injected amounts, the sensitivity of the HPLC-Chip/MS system was about 50 times higher than with the conventional LC-ESI/MS system. The results indicate that the use of HPLC-Chip/MS system is clearly advantageous only in the analysis of low-volume samples. Both methods showed good linearity and good quantitative and chromatographic repeatability. In addition to the instrument comparisons with oxime derivatized steroids, the feasibility of the HPLC-Chip/MS system in the analysis of non-derivatized and oxime derivatized steroids was compared. The HPLC-Chip/MS method developed for non-derivatized steroids was also applied to the quantitative analysis of 15 mouse plasma samples.
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? > Comparison of a HPLC-Chip/MS system to a conventional LC-MS system. > LODs for oxime-derivatized steroids slightly lower with the HPLC-Chip/MS system. > Both methods show good linearity, quantitative performance, and repeatability. > Development of a HPLC-Chip/MS method for analyzing non-derivatized steroids.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 31 January 2012 Yanlin Zhang, Samuel B. Adeloju A rapid flow injection catalytic cold vapour atomic absorption spectrometric (FI-CCV-AAS) method is described for speciation and determination of organic mercury in biological samples. Varying concentrations of NaBH4 were employed for mercury vapour generation from inorganic and mixture of inorganic and organic (total) Hg. The presence of Fe3+, Cu2+ and thiourea had catalytic effect on mercury vapour generation from methylmercury (MeHg) and, when together, Cu2+ and thiourea had synergistic catalytic effect on the vapour generation. Of the two metal ions, Fe3+ gave the best sensitivity enhancement, achieving the same sensitivity for MeHg and inorganic Hg2+. Due to similarity of resulting sensitivity, Hg2+ was used successfully as a primary standard for quantification of inorganic and total Hg. The catalysis was homogeneous in nature, and it was assumed that the breaking of the C-Hg bond was facilitated by the delocalization of the 5d electron pairs in Hg atom. The extraction of MeHg and inorganic mercury (In-Hg) in fish samples were achieved quantitatively with hydrochloric acid in the presence of thiourea and determined by FI-CCV-AAS. The application of the method to the quantification of mercury species in a fish liver reference material DOLT-4 gave 91.4% and 102.3% recoveries for total and methyl mercury, respectively. The use of flow injection enabled rapid analysis with a sample throughput of 180 h-1.
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? Successful speciation of inorganic and organic Hg with Fe, Cuand thiourea as catalysts ? Best sensitivity enhancement and similar sensitivity for MeHg and Hgwith Fe? Successful use of Hgas the primary standard for quantification of inorganic and total-Hg ? Quantitative extraction of Hg and MeHg with 2 M HCl which contained thiourea ? Integration with FIA for rapid analysis with a sample throughput of 180 h.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 31 January 2012 Aldo Polettini, Edward J. Cone, David A. Gorelick, Marilyn A. Huestis BackgroundAlthough hair testing is well established for the assessment of past drug exposure, uncertainties persist about mechanisms of drug incorporation into hair and interpretation of results. The aim of this study was to administer methamphetamine (MAMP) under controlled conditions as a model drug to investigate drug incorporation into human hair.Material and MethodsSeven volunteers with a history of stimulant use received 4 × 10 mg (low) doses of sustained release S-(+)-MAMP HCl within one week, with weekly head hair samples collected by shaving. 3 weeks later, 4 of them received 4 × 20 mg (high) doses. After extensive isopropanol/phosphate buffer washing of the hair, MAMP and its metabolite amphetamine (AMP) concentrations were determined in all weekly hair samples by LC-MS-MS in selected reaction monitoring mode with the undeca- and deca-deuterated drugs, respectively, as internal standards (LLOQ, 0.005 ng/mg).ResultsMAMP Tmaxoccurred from 1 to 2 weeks after both doses, with Cmaxranging from 0.6-3.5 ng/mg after the low and 1.2-5.3 ng/mg after the high MAMP doses. AMP Cmaxin hair was 0.1-0.3 ng/mg and 0.2-0.5 ng/mg, respectively, for low and high doses. Highly dose–related concentrations within subjects, but large variability between subjects were observed. MAMP concentrations were above the 0.2 ng/mg cutoff for at least two weeks following administration of both low and high doses. The overall AMP/MAMP ratio ranged from 0.07 to 0.37 with a mean value of 0.15 ± 0.07, and a median of 0.13. The percentage of MAMP and AMP removed with the washing procedure decreased with time after administration. A strong correlation was found between area under the curve of MAMP (r = 0.90, p = 0.00) and AMP (r = 0.94, p = 0.00) concentrations calculated for the 3-week period following administration and the total melanin concentration in hair. Significant correlations were observed also between Cmaxand melanin.ConclusionsThis study demonstrated that despite large inter-individual differences, the incorporation of MAMP and AMP into hair is dose-related with much of the observed scatter of MAMP and AMP concentrations explained by melanin concentration in hair.
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? HIghlight ? We studied in vivo incorporation of methamphetamine in human head hair ? Methamphetamine (40 and 80 mg) was administered under controlled conditions ? methamphetamine and amphetamine incorporation was followed for 3 weeks ? Influence of various factors (e.g. pre-analytical washing, melanin) was studied ? Criteria to ascertain MAMP use based on MAMP/AMP ratio and AMP cutoff are proposed
Publication year: 2012 Source: Analytica Chimica Acta, Available online 29 January 2012 Oluwasesan Adegoke, Eric Hosten, Cedric McCleland, Tebello Nyokong A novel bromide ion -selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)–functionalized CdTe quantum dots (QDs–4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions were investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01–0.13 ?M. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
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A bromide ion -selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)–functionalized CdTe quantum dots (QDs–4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery
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? Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide ? Quantum dots fluorescence is quenched by the radical ? In the presence of bromide ions the fluorescence is restored ? The sensor is more selective to bromine ions than other common ions
Publication year: 2012 Source: Analytica Chimica Acta, Available online 27 January 2012 David Caballero, Elena Martinez, Joan Bausells, Abdelhamid Errachid, Josep Samitier In this work we report the fabrication and characterization of a label-free impedimetric immunosensor based on a silicon nitride (Si3N4) surface for the specific detection of human serum albumin (HSA) proteins. Silicon nitride provides several advantages compared with other materials commonly used, such as gold, and in particular in solid-state physics for electronic-based biosensors. However, few Si3N4-based biosensors have been developed; the lack of an efficient and direct protocol for the integration of biological elements with silicon-based substrates is still one of its the main drawbacks. Here, we use a direct functionalization method for the direct covalent binding of monoclonal anti-HSA antibodies on an aldehyde-functionalized Si-p/SiO2/Si3N4structure. This methodology, in contrast with most of the protocols reported in literature, requires less chemical reagents, it is less time-consuming and it does not need any chemical activation. The detection capability of the immunosensor was tested by performing non-faradaic electrochemical impedance spectroscopy (EIS) measurements for the specific detection of HSA proteins. Protein concentrations within the linear range of 10–10 M were detected, showing a sensitivity of 0.128 ? ?Mand a limit of detection of 10 M. The specificity of the sensor was also addressed by studying the interferences with a similar protein, bovine serum albumin. The results obtained show that the antibodies were efficiently immobilized and the proteins detected specifically, thus, establishing the basis and the potential applicability of the developed silicon nitride-based immunosensor for the detection of proteins in real and more complex samples.
Highlights
? An impedimetric label-free immunosensor was developed for the specific detection of human serum albumin proteins. ? Anti-HSA antibodies were covalently immobilized on silicon nitride surfaces using a direct functionalization methodology. ? Silicon nitride offers multiple advantages compared to other common materials. ? The proposed sensor has high sensitivity and good selectivity for the detection of HSA proteins.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 27 January 2012 Cong Qin, Chao Chen, Qingji Xie, Lihua Wang, Xiuhui He, ... Sodium alginate (AlgNa) and poly(diallyldimethylammonium chloride) (PDDA) were mixed to obtain an interpenetrating polymer composite via electrostatic interaction and then cast on an Au electrode surface, followed by incorporation of metal ions (e.g. Feor Ca, to form AlgFe or AlgCa hydrogel) and glucose oxidase (GOx) (or lactate oxidase (LOx)), to prepare amperometric enzyme electrodes. The interactions of PDDA, Alg, and Feare studied by visual inspection as well as microscopic and electrochemical methods. Under optimized conditions, the PDDA-AlgFe-enzyme/Au and PDDA-AlgCa-enzyme/Au electrodes can give good analytical performance (e.g. nM-scale limit of detection of glucose or lactate, and sensitivities > 50 ?A cm mM) in the first generation biosensing mode, which are better than the reported analogues using typical polysaccharide biopolymers as enzyme-immobilization matrices. The enzyme electrodes also worked well in the second generation biosensing mode in the coexistence ofp-benzoquione or ferrocene monocarboxylic acid artificial mediator. Biofuel cells (BFCs) with the enzyme electrodes as the bioanodes and glucose (or lactate) as the biofuel were also fabricated with satisfactory results. The proposed protocols for preparation of high performance Alg-based biocomposites may find wide applications in bioanalysis.
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? highlights ? Poly(diallyldimethylammonium)-alginate-metal ion-enzyme biocomposites are prepared. ? The biocomposites are studied by microscopic/electrochemical methods. ? Amperometric enzyme electrodes of glucose and lactate are thus developed. ? The enzyme electrodes works well for biosensing of glucose and lactate. ? The enzyme electrodes works well as bioanodes for biofuel cells of glucose and lactate.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 27 January 2012 Joanne Chung Yan Yeung, Inés de Lannoy, Brad Gien, Dajana Vuckovic, Yingbo Yang, ... In vivosolid-phase microextraction (SPME) can be used to sample the circulating blood of animals without the need to withdraw a representative blood sample. In this study,in vivoSPME in combination with liquid-chromatography tandem mass spectrometry (LC-MS/MS) was used to determine the pharmacokinetics of two drug analytes, R,R-fenoterol and R,R-methoxyfenoterol, administered as 5 mg/kgi.v.bolus doses to groups of 5 rats. This research illustrates, for the first time, the feasibility of the diffusion-based calibration interface model forin vivoSPME studies. To provide a constant sampling rate as required for the diffusion-based interface model, partial automation of the SPME sampling of the analytes from the circulating blood was accomplished using an automated blood sampling system. The use of the blood sampling system allowed automation of all SPME sampling stepsin vivo, except for the insertion and removal of the SPME probe from the sampling interface. The results fromin vivoSPME were compared to the conventional method based on blood withdrawal and sample clean up by plasma protein precipitation. Both whole blood and plasma concentrations were determined by the conventional method. The concentrations of methoxyfenoterol and fenoterol obtained by SPME generally concur with the whole blood concentrations determined by the conventional method indicating the utility of the proposed method. The proposed diffusion-based interface model has several advantages over other kinetic calibration models forin vivoSPME sampling including (i) it does not require the addition of a standard into the sample matrix duringin vivostudies, (ii) it is simple and rapid and eliminates the need to pre-load appropriate standard onto the SPME extraction phase and (iii) the calibration constantfor SPMEcan be calculated based on the diffusion coefficient, extraction time, fibre length and radius, and size of the boundary layer. In the current study, the experimental calibration constants of 338.9 ± 30 mmand 298.5 ± 25 mmare in excellent agreement with the theoretical calibration constants of 307.9 mmand 316.0 mmfor fenoterol and methoxyfenoterol respectively.
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?In vivoSPME was used for PK studies of fenoterol and methoxyfenoterol in rats. ? New diffusion-based calibration interface model was used for calibration. ? Automated sampling system was used forin vivostudies. ? First timein vivoSPME was used for studies of hydrophilic drugs.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 27 January 2012 Hasina Yasmin, Takayuki Shibata, Mohammed Shafikur Rahman, Tsutomu Kabashima, Masaaki Kai A novel fluorescence (FL) reaction forN-terminal Gly-containing peptides has been developed using 3,4-dihydroxyphenylacetic acid (3,4-DHPAA). The reaction of the peptides with 3,4-DHPAA was carried out in borate buffer (pH 8.0) in the presence of sodium periodate at 37 °C for 10 min, and the FL was measured with a spectrofluorimeter at the excitation and emission wavelengths of 370 nm and 465 nm, respectively. The 3,4-DHPAA reagent generated particularly strong FL for peptides containing Gly at theirN-termini. When various other bio-substances, such as amino acids, sugars, nucleic bases, nucleotides, and proteins, were reacted with 3,4-DHPAA, no FL was observed. Under optimized reaction conditions, the lower detection limit of 0.25 ?mol Lwas obtained for theN-terminal Gly-containing peptides of Gly-Pro (GP) and Gly-Pro-Pro (GPP), which gave 3 times greater FL intensity than that observed for the reagent blank. The proposed reaction with 3,4-DHPAA as a fluorogenic reagent is selective and sensitive for the detection ofN-terminal Gly-containing peptides, and therefore, this method could be a useful tool for the determination of these particular oligopeptides.
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Highlights
? 3,4-Dihydroxyphenylacetic acid was found to produce fluorescence with peptides. ? The reaction proceeded in the presence of sodium periodate and borate buffer at 37 °C. ? Peptides containing Gly at their N-termini provided stronger fluorescence. ? A lower detection limit of 0.25 ?mol Lwas obtained with peptides GP and GPP. ? Almost none of the other biomolecules including proteins showed fluorescence.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 25 January 2012 Della W.M. Sin, Pui-kwan Chan, Samuel T.C. Cheung, Yee-Lok Wong, Siu-kay Wong, ... This paper presents the preparation of a candidate certified reference material (CRM) of cypermethrin in green tea, GLHK-11-01a according to the requirements of ISO Guide 34 and 35. The certification of the material was performed using a newly developed isotope dilution mass spectrometry (IDMS) approach, with gas chromatography high resolution mass spectrometry (GC-HRMS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). Statistical analysis (one-way ANOVA) showed excellent agreement of the analytical data sets generated from the two mass spectrometric detections. The characterization methods have also been satisfactorily applied in an Asia Pacific Metrology Program (APMP) interlaboratory comparison study. Both the GC-HRIDMS and GC-IDMS/MS methods proved to be sufficiently reliable and accurate for certification purpose. The certified value of cypermethrin in dry mass fraction was 148 ?g kgand the associated expanded uncertainty was 14 ?g kg. The uncertainty budget was evaluated from sample inhomogeneity, long-term and short-term stability and variability in the characterization procedure. GLHK-11-01a is primarily developed to support the local and wider testing community on need basis in quality assurance work and in seeking accreditation.
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? A cypermethrin CRM in green tea was developed ? Using two isotope dilution mass spectrometry techniques for characterization ? Certified value of 148 ?g kgwith expanded uncertainty of ±9.2% ? Support quality assurance of cypermethrin analysis in tea to testing community.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 25 January 2012 Jian-hua Tang, Lian Xie, Bin Zhang, Ting Qiu, Bin Qi, ... Based on the polyelectrolyte-protected CdTe quantum dots (QDs), which were prepared by self-assembling of QDs and poly-diallyldimethylammonium chloride (PDADMAC) in the help of electrostatic attraction, the strong fluorescence silica nanoparticles (QDs-PDADMAC@SiO2) have been prepared via a water-in-oil reverse microemulsion method. Transmission electron microscopy andZetapotential analysis were used to characterize the as-prepared nanoparticles. All of the particles were almost spherical and there is a uniform distribution of the particle size with the average diameter about 25 nm. There is a largeZetapotential of -35.07 mV which is necessary for good monodispersity of nanoparticles solution. As compared with the QDs coated by SiO2(QDs@SiO2), the QDs-PDADMAC@SiO2nanoparticles have much stronger fluorescence, and their fluorescence stability could be obviously improved. Moreover, QDs-PDADMAC@SiO2exhibits good biological compatibility which promotes their application in cellular imaging
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The staining effect of the control group (a), QDs@SiO2 (b) and QDs-PDADMAC@SiO2(c)
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? The fluorescence intensity of QDs-PDADMAC@SiO2is stronger than that of QDs@SiO2. ? The fluorescence stability of QDs-PDADMAC@SiO2is better than that of QDs@SiO2. ? The cytotoxicity of QDs-PDADMAC@SiO2was lower than that of QDs@SiO2 ? The staining effect of QDs-PDADMAC@SiO2was much better than that of QDs@SiO2
Publication year: 2012 Source: Analytica Chimica Acta, Available online 24 January 2012 M. Vilanova, E. Campo, A. Escudero, M. Graña, A. Masa, ... The aroma and volatile composition of wines from five red cultivars from NW Spain (Brancellao, Mencía, Merenzao, MouratónandSousón) has been studied by Gas Chromatography Mass Spectrometry (GC-MS) and sensory descriptive analysis (SDA) during three consecutive vintages (2007-2009) in order to characterize these wines. In addition, relationships between the instrumental (volatile) and sensory variables were analyzed through the application of partial least squares regression (PLSR). Results revealed that the effect of “cultivar” was very important as a third of compounds (16 in total) varied significantly (p ? 0.05) among varieties.Mencíawines presented the highest concentrations of?-nonalactone, whereasSousónwines were the richest in monoterpene compounds. On the contrary, no significant difference was observed with respect to the esters content, probably as a consequence of using the same yeast for all vinifications. Twenty out of fifty one quantified volatile compounds were present in some samples at concentrations higher than their corresponding odour thresholds (OAV >1), thus contributing to the final wine aroma. Partial Least Square (PLS) regression was applied to volatile compounds with OAV > 0.2 and aroma descriptors with %GM > 10. PLSR yielded a satisfactory model for the prediction of four important aroma descriptors in this set of wines - aroma quality, aroma intensity, herbaceous and red fruit - from instrumental analysis data. This work contributes to gaining knowledge about the sensory profiles and its relation to the volatile composition of minority Galician red grape cultivars.
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Partial least squares regression (PLSR1) product space volatile compounds with OAV > 0.2 and significant aroma descriptors (a) aroma intensity, (b) aroma quality, (c) herbaceous and (d) red fruit.
Highlights
? Aroma ofVitis viniferared cultivars from NW Spain were studied by GC-MS and sensory analysis ? PLSR was a satisfactory model for prediction aroma descriptors from instrumental data ? This work contribute to knowledge about sensory and volatile composition of minority grape cultivars.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 24 January 2012 Xu-Cheng Fu, Ju Wu, Li Nie, Cheng-Gen Xie, Jin-Huai Liu, ... Electrochemical detection of Hg(II) using a electropolymerized ion imprinting poly(2-mercaptobenzothiazole) films at the surface of gold nanoparticles/single-walled carbon nanotubes nanohybrids modified glassy carbon electrode (PMBT/AuNPs/SWCNTs/GCE) is described for the first time. The Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor exhibits larger binding to functionalized capacity, larger affinity, faster binding kinetics and higher selectivity to template Hg(II). The differential pulse anodic stripping voltammetry (DPASV) response of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor to Hg(II) is ca. 3.7 and 10.5 fold higher than that at the non-imprinted PMBT/AuNPs/SWCNTs/GCE and the imprinted PMBT/AuNPs/GCE, respectively; and the detection limit for Hg(II) is 0.08 nM (S/N = 3, which is well below the guideline value given by the World Health Organization) and a sensitivity of 0.749 ?A nMwas obtained. Excellent wide linear range (0.4-96.0 nM) and good repeatability (relative standard deviation of 2.6%) were obtained for Hg(II). The interference experiments show that Ag(I), Pb(II), Cd(II), Zn(II) and Cu(II) had little or no influence on the Hg(II) signal. These values, particularly the high sensitivity and excellent selectivity in contrast to the values reported previously in the area of electrochemical Hg(II) detection, demonstrate the analytical performance of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE toward Hg(II) is superior to the existing electrodes and could be used for efficient determination of Hg(II) in natural water samples
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? Ion imprinting films on AuNPs/SWCNTs/GCE ? High sensitivity and selectivity for Hg(II) detection ? Regeneration easily ? Good repeatability and stability ? Could be exploited for on-line detection of Hg(II)
Publication year: 2012 Source: Analytica Chimica Acta, Available online 24 January 2012 ?ukasz Tymecki, Magdalena Rejnis, Marta Pokrzywnicka, Kamil Strzelak, Robert Koncki Two compact optoelectronic fluorimetric devices operating according to the paired-emitter-detector-diode concept have been developed. The fluorimetric detector, fabricated of three light emitting diodes only, has been applied for fluorimetric optosensor development by further integration with sensing solid phase. In these investigations as a model analyte and as a model sensing layer useful for solid phase spectrometry, riboflavin and C18-silica have been chosen, respectively. Both developed analytical devices have been applied for non-stationary fluorimetric measurements performed under conditions of flow injection analysis. The presented flow-through detector and sensor operating under given flow conditions offer riboflavin detection in mg Land ?g Lranges of concentration, respectively.
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? Flow-through fluorimetric detector made of three LEDs only is presented. ? The detector applied in FIA manifold is useful for pharmaceutical analysis. ? Solid phase spectrometry with the detector leads to optosensor development.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 24 January 2012 Elli Tyrkkö, Anna Pelander, Ilkka Ojanperä A liquid chromatography (LC) retention time prediction software, ACD/ChromGenius, was employed to calculate retention times for structural isomers, which cannot be differentiated by accurate mass measurement techniques alone. For 486 drug compounds included in an in-house database for urine drug screening by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOFMS), a retention time knowledge base was created with the software. ACD/ChromGenius calculated retention times for compounds based on the drawn molecular structure and given chromatographic parameters. The ability of the software for compound identification was evaluated by calculating the retention order of the 118 isomers, in 50 isomer groups of 2-5 compounds each, included in the database. ACD/ChromGenius predicted the correct elution order for 68% (34) of isomer groups. Of the 16 groups for which the isomer elution order was incorrectly calculated, two were diastereomer pairs and thus difficult to distinguish using the software. Correlation between the calculated and experimental retention times in the knowledge base tested was moderate, r = 0.8533. The mean and median absolute errors were 1.12 min, and 0.84 min, respectively, and the standard deviation was 1.04 min. The information generated by ACD/ChromGenius, together with otherin silicomethods employing accurate mass data, makes the identification of substances more reliable. This study demonstrates an approach for tentatively identifying compounds in a large target database without a need for primary reference standards.
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? Structural isomers indistinguishable by accurate mass measurement techniques alone. ? Evaluation of a retention time prediction software for isomer differentiation. ? Software calculated correct elution order for 68% of isomer groups. ? Retention order predictions bring valuable data for isomer separation. ? Tentative compound identification possible without reference standard.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 24 January 2012 A. Taylor, W.H.Blake, M.J. Keith-Roach The application of cosmogenicBe as a sediment tracer at the catchment-scale requires an understanding of its geochemical associations in soil to underpin the assumption of irreversible adsorption. Sequential extractions offer a readily accessible means of determining the associations ofBe with operationally-defined soil phases. However, the subdivision of the low activity concentrations of falloutBe in soils into geochemical fractions can introduce high gamma counting uncertainties. Extending analysis time significantly is not always an option for batches of samples, owing to the on-going decay ofBe (t1/2 = 53.3 days).Here, three different methods of preparing and quantifyingBe extracted using the optimised BCR three-step scheme have been evaluated and compared with a focus on reducing analytical uncertainties. The optimal method involved carrying out the BCR extraction in triplicate, sub-sampling each set of triplicates for stable Be analysis before combining each set and coprecipitating theBe with metal oxyhydroxides to produce a thin source for gamma analysis. This method was applied to BCR extractions of naturalBe in four agricultural soils. The approach gave good counting statistics from a 24 hour analysis period (?10% (2?) where extract activity > 40% of total activity) and generated statistically useful sequential extraction profiles. Total recoveries ofBe fell between 84–112%. The stable Be data demonstrated that the extraction procedure had a high reproducibility (< 1% RSD), thus gamma counting uncertainties dominated the overall uncertainty.In addition, extractions of soil equilibrated with stable Be at a concentration below the Cation Exchange Capacity (CEC) of the soil demonstrated that doubling the soil:solution ratio to enhance the mass of soil used in a sequential extraction scheme affects the apparent distribution of approximately 10% of the total Be. At high concentration, stable Be was found to be a poor proxy forBe fallout in sequential extractions.
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Showing decrease in analytical uncertainty using the optimal (combined preconcentrated sample extract) method. nv (no value) where extract activities were < Minimum Detectable Activity
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? Knowledge ofBe geochemical behaviour is required to support tracer studies ? Sequential extraction with naturalBe returns high analytical uncertainties ? Preconcentrating extracts from a large sample mass improved analytical uncertainty ? This optimised method can be readily employed in studies using low activity samples
Publication year: 2012 Source: Analytica Chimica Acta, Available online 24 January 2012 Antonio Nebbioso, Alessandro Piccolo We size fractionated a soil humic acid (HA) by preparative high performance size exclusion chromatography (HPSEC) and evaluated the analytical capacity of humeomics to isolate and identify humic molecular components in the separated size-fractions. HA and its three size-fractions were chemically fractionated to extract non-covalently bound organosoluble compounds (ORG1), weakly ester-bound organosoluble (ORG2) and hydrosoluble constituents (AQU2), strongly ester-bound organosoluble components (ORG3), and final unextractable residues (RES4). According to their solubility, the extracts were characterized by either GC-MS or on-line thermochemolysis/GC-MS techniques. The humeomic sequence showed that the analytical yields of identified compounds in either ORG or AQU extracts of size-fractions were invariably larger than for the unfractionated HA. This was attributed to a weaker conformational stability of humic suprastructures obtained by HPSEC fractionation, thereby enabling an improved separation and identification of single humic molecules. In line with the supramolecular understanding of humic substances, we found that hydrophobic compounds were mainly distributed in the largest size-fraction, while hydrophilic components were eluted in the smallest size-fraction. Furthermore, compounds with linear chains or stackable aromatic rings associated in regular structures were more abundant in the former fraction, whereas irregularly shaped compounds, that hindered association in larger size, were mostly found in the latter fraction. Thus the structural characteristics of single humic molecules determined their mutual association in humic suprastructures, as well as their conformational strength and shape. The lack ofde-novosynthesized macropolymers in the unfractionated soil humic matter was confirmed by the absence of RES4 fractions in the separated size-fractions. Our results indicate that humeomics capacity to reveal the complex molecular composition of humic suprastructures was significantly improved by subjecting humic matter to a preliminary HPSEC fractionation.
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Highlights
? Humeomics applied to size-fractions of a humic material separated by HPSEC. ? Enhanced analytical yield and detection of single humic molecules. ? Humeomics increased for weaker conformational stability of humic associations. ? Role played by single molecules in stabilizing humic supramolecular associations. ? Realistic structure-activity relatiosnship.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 24 January 2012 Huiyong Wang, Erin J. Walaszczyk, Ke Li, Yu-Wen Chung-Davidson, Weiming Li We present a comparison of two sensitive methods, HPLC with fluorescence detector (HPLC/FLD) and UPLC with electrospray tandem mass spectrometry (UPLC/MS/MS), for the determination of indoleamine neurotransmitters (NTs) and their metabolites in sea lamprey plasma samples. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) were also tested for recovery and matrix effect. The recoveries of SPE determined by HPLC/FLD and UPLC/MS/MS ranged from 75 to 123% and 78 to 105%, respectively, while the recoveries of LLE ranged from 45 to 73% and 48 to 75%, respectively. SPE combined with HPLC/FLD and UPLC/MS/MS to determine the target analytes in plasma samples were validated of the sensitivity, reproducibility, accuracy and precision. Both methods exhibited excellent linearity in the range of 0.2 ng/mL to 50 ng/mL for all analytes. The limits of detection (LODs) varied from 0.04 ng/mL to 0.13 ng/mL for HPLC/FLD method and 0.003 ng/mL to 0.02 ng/mL for UPLC/MS/MS method. The inter-day accuracy ranged from 82.5 to 127.0% for HPLC/FLD and 93.0 to 113.0% for UPLC/MS/MS. The inter-day precision ranged from 9.9 to 32.3% for HPLC/FLD and 5.4 to 13.2% for UPLC/MS/MS. These results demonstrated that the values obtained by both methods were within the satisfactory range and the UPLC/MS/MS method provided more accurate and precise measurements than HPLC/FLD method. The comparison is of great importance to determine the available detectors, considering the complexity and expensiveness versus quality parameters. These two methods were applied to the analysis of four important indoleamine neurotransmitter analytes (5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, tryptamine and melatonin) in sea lamprey plasma samples.
Graphical abstract
Sensitivity comparison of UPLC-MS/MS and HPLC/FLD method for the determination of melatonin
Highlights
? Compared two sensitive analytical methods: HPLC/FLD and UPLC/MS/MS ? Reported firstly on the measurements of neurotransmitters in the sea lamprey by two methods ? Studied recovery and matrix effects of SPE and LLE ? Determined four indoleamine neurotransmitters ? Analyzed plasma samples from sea lampreys
Publication year: 2012 Source: Analytica Chimica Acta, Available online 20 January 2012 Yali Yuan, Haijuan Li, Shuang Han, Lianzhe Hu, Saima Parveen, ... Electrochemiluminescence (ECL) of ruthenium complexes has broad applications and the immobilization of Ru(bpy)3has received extensive attention. In comparison with Ru(bpy)3, Ru(phen)3can be immobilized more easily because of its better adsorbability. In this study, immobilization of Ru(phen)3for ECL analysis has been demonstrated for the first time by using graphene oxide (GO) as an immobilization matrix. The immobilization of Ru(phen)3is achieved easily by mixing Ru(phen)3with GO without using any ion exchange polymer or covalent method. The strong binding of Ru(phen)3with GO is attributed to both the ?-? stacking interaction and the electrostatic interaction. The Ru(phen)3/GO modified electrode was characterized by using tripropylamine (TPA) as the coreactant. The linear range of TPA is from 3 × 10to 3 × 10 mol/L with the detection limit of 3 × 10 mol/L. The ECL sensor demonstrates outstanding long-term stability. After the storage in the ambient environment for 90 days, the ECL response remains comparable with its original signal
Graphical abstract
Highlights
? Ru(phen)3-based regenerable ECL sensor has been demonstrated for the first time. ? Ru(phen)3has better adsorbability than Ru(bpy)3. ? Ru(phen)3is readily and strongly immobilized on graphene oxide by adsorption. ? Ru(phen)3/GO regenerable sensor has excellent long-term stability. ? Ru(phen)3is an attractive alternative to Ru(bpy)3for regenerable ECL sensors
Publication year: 2012 Source: Analytica Chimica Acta, Available online 20 January 2012 Bing Xu, Zhisheng Wu, Zhaozhou Lin, Chenglin Sui, Xinyuan Shi, ... Ethanol precipitation plays a major role in the pretreatment of Flos Lonicerae Japonicae of Qingkailing injection, and is also one of the most popular purification techniques in Chinese herbal medicines. In order to monitor and have a better understanding of the ethanol precipitation process, a PLS model was built based on NIR spectroscopy and HPLC analysis of Chlorogenic acid content within the framework of FDA's PAT initiative. Nevertheless, due to the complex mechanism of and the raw materials’ natural variability introduced into the ethanol precipitation process, it was unable to foresee the variations in new batches which may jeopardize the robustness of the established model. Therefore, based on the simple interval calculation (SIC) theory, a new model expansion updating strategy which could continuously expand the variation coverage of the calibration model along with the batch proceeding of ethanol precipitation process was proposed. Effects of model updating were validated by an individual batch with 60 samples. After two times of updating, the root mean squared error of prediction (RMSEP) decreased from 0.268 mg·mLto 0.199 mg·mL, while the insiders in the object status plot (OSP) increased from 44 to 58, demonstrating the good performance of the proposed approach.
Graphical abstract
Highlights
? NIR analysis for Low content of API in ethanol precipitation process is verified. ? A dynamic PLS model updating strategy is brought forward. ? Simple interval calculation (SIC) theory is coupled into the updating strategy. ? Effectiveness of model updating is visualized by object status plot (OSP)
Publication year: 2012 Source: Analytica Chimica Acta, Available online 19 January 2012 Qiang Gao, Hao-Bo Zheng, Dan Luo, Jun Ding, Yu-Qi Feng In this work, we proposed a simple co-mixing method to fabricate magnetic one-dimensional polyaniline (denoted as 1D-PANIs/MNPs). One-dimensional polyanilines (1D-PANIs) and magnetic nanoparticles (MNPs) were prepared by chemical oxidation and solvothermal methods, respectively. When MNPs and 1D-PANIs (with mass ratio 4:1) were co-mixed and vortexed evenly in a solvent (e.g., ethanol, water, acetonitrile), they could assemble into 1D-PANIs/MNPs spontaneously and thus be magnetically separable. To testify the feasibility of 1D-PANIs/MNPs in sample preparation, it was applied as the sorbent for magnetic solid phase extraction (MSPE) of fluoroquinolones (FQs) in honey samples. Under optimized conditions, a rapid, convenient, and efficient method for the determination of four FQs in honey samples by 1D-PANIs/MNPs-based MSPE coupling with high performance liquid chromatography with fluorescence detection (HPLC-FLD) was established. The limits of detection (LODs) for four FQs ranged from 0.4 to 1.4 ng/g. The intra- and interday relative standard deviations (RSDs) were less than 17.6%. The recoveries of FQs for three spiked honey samples ranged from 86.3 to 121.3%, with relative standard deviations (RSDs) of less than 16.3%.
Graphical abstract
By mixing magnetic nanoparticles (MNPs) and one-dimensional polyanilines (1D-PANIs) in a solvent, magnetic one-dimensional polyanilines (1D-PANIs/MNPs) were formed facilely due to the encapsulation of magnetic nanoparticles into the interconnected network of o1D-PANIs. The 1D-PANIs/MNPs have been demonstrated to be applicable for magnetic solid-phase extraction.
Highlights
? Magnetic 1D polyaniline (1D-PANIs/MNPs) was prepared by a simple co-mixing method? Efficacy of 1D-PANIs/MNPs for isolating four fluoroquinolones (FQs) from honey was tested? The optimized conditions were established for 1D-PANIs/MNPs-based magnetic solid-phase extraction (MSPE)? ?-? and hydrophobic interactions played a dominant role to the retention between the FQs and 1D-PANIs/MNPs? A simple, rapid, and effective MSPE-HPLC analysis method for FQs in honey samples was developed
Publication year: 2012 Source: Analytica Chimica Acta, Available online 18 January 2012 Admira Bosnjakovic, Manoj K. Mishra, Hye Jung Han, Roberto Romero, Rangaramanujam M. Kannan A dendrimer-based sandwich type enzyme-linked immunosorbent assay (ELISA) was developed for the improved detection of recombinant human tumor necrosis factor-alpha (TNF-?) for early diagnosis of perinatal diseases. Hydroxyl-terminated generation four poly(amidoamine) dendrimer (G4-OH) was used for the development of a solid phase bio-sensing platform. The surface of the ELISA plate was modified with polyethylene-glycol (PEG) and thiol-functionalized G4-OH was immobilized on the PEG-functionalized plate. A capture antibody was oxidized and covalently immobilized onto the dendrimer-modified ELISA plate, which provides favorable orientation for the antigen binding sites towards the analyte. The dendrimer-modified plate showed enhanced sensitivity, and the detection limit for TNF-? was found to be 0.48 pg mL, which is significantly better than the commercially available ELISA kit. The selectivity of the dendrimer-modified ELISA plate was further evaluated with a mixture of cytokines, which showed results for similar to that of TNF-? alone. The modified plate provides a greater opportunity for the detection of a wide range of cytokines and biomarkers.
Graphical abstract
Highlights
? Sensitive, early detection of cytokines can help in identifying perinatal diseases. ? Appropriately grafted dendrimer on the biosensor leads to better antibody orientation. ? Significantly improved detection limit and sensitivity has been shown for TNF-?. ? Platform approach is adaptable to both capture and detection, and for a wide variety of cytokines.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 18 January 2012 Jiangtao Peng, Silong Peng, Yong Hu A novel outlier detection method in partial least squares based on random sample consensus is proposed. The proposed algorithm repeatedly generates partial least squares solutions estimated from random samples and then tests each solution for the support from the complete dataset for consistency. A comparative study of the proposed method and leave-one-out cross validation in outlier detection on simulated data and near-infrared data of pharmaceutical tablets is presented. In addition, a comparison between the proposed method and PLS, RSIMPLS, PRM is provided. The obtained results demonstrate that the proposed method is highly efficient.
Graphical abstract
Graphical abstract
Highlights
? A novel outlier detection method in partial least squares based on random sample consensus is proposed. ? The proposed algorithm repeatedly generates PLS solutions estimated from random samples and then tests each solution for the support based on PLS residuals. ? It models inlier error as an unbiased Gaussian distribution and outlier error as a uniform distribution. ? Compared with the classic PLS and robust methods such as RSIMPLS and PRM, the proposed PLSSAC method shows comparable performance.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 18 January 2012 Zhenzhong Yang, Yufeng Zhang, Lijuan Sun, Yi Wang, Xiumei Gao, ... Tyrosinase is a key enzyme in melanin synthesis. Its inhibitor may be used to efficiently treat hyperpigmentation and widely applied in cosmetic products and food supplements. In the present study, a new assay based on ultrafiltration high-performance liquid chromatography coupled with diode array detector and mass spectrometry (HPLC-DAD-MS) was developed for the rapid screening and identification of ligands for tyrosinase. Experiments were carried out to select the optimal binding conditions, tyrosinase concentration, and incubation time. Non-specific binding to the denatured tyrosinase was also investigated. Twelve compounds with tyrosinase binding activity were found in mulberry leaf extracts. The identities of these compounds were characterised by HPLC-DAD-MS. Particularly, two compounds, namely, quercetin-3-O-(6-O-malonyl)-?-D-glucopyranoside and kaempferol-3-O-(6-O-malonyl)-?-D-glucopyranoside, were identified as new tyrosinase inhibitors. The screening results were verified by tyrosinase inhibition assays. Experimental results proved that the proposed method could rapidly screen tyrosinase inhibitors in complex mixtures
Graphical abstract
Highlights
? A new assay based on ultrafiltration HPLC-DAD-MS has been developed for rapid screening and identification of ligands for tyrosinase. ? Experiments were carried out to select the optimum binding conditions. ? Twelve compounds with tyrosinase binding activity were found from extract of mulberry leaves. ? Two malonyl-glycosylflavones were identified as new tyrosinase inhibitors
Publication year: 2012 Source: Analytica Chimica Acta, Available online 18 January 2012 Zhenkun Lin, Wenjing Cheng, Yanyan Li, Zhiren Liu, Xiangping Chen, ... Leakage of the residual template molecules is one of the biggest challenges for application of molecularly imprinted polymer (MIP) in solid-phase extraction (SPE). In this study, bisphenol F (BPF) was adopted as a dummy template to prepare MIP of bisphenol A (BPA) with a superparamagnetic core-shell nanoparticle as the supporter, aiming to avoid residual template leakage and to increase the efficiency of SPE. Characterization and test of the obtained products (called mag-DMIP beads) revealed that these novel nanoparticles not only had excellent magnetic property but also displayed high selectivity to the target molecule BPA. As mag-DMIP beads were adopted as the adsorbents of solid-phase extraction for detecting BPA in real water samples, the recoveries of spiked samples ranged from 84.7 to 93.8% with the limit of detection of 2.50 pg mL, revealing that mag-DMIP beads were efficient SPE adsorbents.
Graphical abstract
BPF was adopted as a dummy template to prepare BPA-MIP with a superparamagnetic core-shell nanoparticle as the supporter, which was approved to be an efficient SPE adsorbent.
Highlights
? BPF was used as a dummy template to prepare BPA-MIP. ? A superparamagnetic core-shell nanoparticle was designed as MIP supporter. ? A method for BPA extraction from water sample was provided. ? MIP bead was proved to be an efficient SPE adsorbent.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 18 January 2012 Ali Sarafraz-Yazdi, Amirhassan Amiri, Gholamhossein Rounaghi, Hossein Eshtiagh-Hosseini In this study, poly(ethylene glycol) (PEG) grafted multi-walled carbon nanotubes (PEG-g-MWCNTs) were synthesized by the covalent functionalization of MWCNTs with hydroxyl-terminated PEG chains. PEG-g-MWCNTs was used as a novel stationary phase to prepare the sol–gel solid-phase microextraction (SPME) fiber in combination with gas chromatography-flame ionization detector (GC–FID) for the determination of ibuprofen, naproxen and diclofenac in real water samples.Some parameters which influencing the extraction efficiency were such as desorption temperature and time, extraction temperature and time, pH, salt effect and stirring speed that were investigated and optimized. Under the optimal conditions, the method detection limits (S/N = 3) were in the range of 0.007–0.03 ng mLand the limits of quantification (S/N = 10) between 0.05–0.07 ng mL. The relative standard deviations (RSDs) for one fiber (Repeatability) (n = 5) were obtained from 5.9 up to 8.1% and between fibers or batch to batch (n = 3) (Reproducibility) in the range of 7.2–9.1%. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples at 0.2 ng mLwere from 84 to 107%.
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Highlights
? A new, simple and sensitive method for determining NSAIDs was proposed. ? SPME based on sol-gel technology was proposed for the determination of NSAIDs. ? PEG-g-MWCNTs was used as stationary phase to prepare the sol–gel SPME fiber. ? This method has a considerably low LOD and a relatively wide linear rang.
Publication year: 2012 Source: Analytica Chimica Acta, Available online 17 January 2012 Carmen Ibáñez-Palomino, José Fermín López-Sánchez, Angels Sahuquillo The usefulness of a certified reference material (CRM) for analytical method validation and quality control purposes is attributed mainly to its key properties, namely homogeneity and stability. However, it is also advisable to select suitable CRMs in terms of representativeness. To assess the representativeness of a CRM for analytical mercury speciation, a number of aspects must be considered in regard to the routine samples analyzed: the origin of the matrix, the type of mercury species and the level of concentration.This review critically analyzes the availability of current CRMs for mercury speciation analysis in environmental and biological fields. The characteristics of the CRMs are compared with the matrices and samples covered in papers published in the last five years on mercury speciation, mainly in water, soils, sediments, sewage sludge, seafood, blood, urine and hair.
Graphical abstract
Highlights
? We review the application and usefulness of current CRMs for analytical mercury speciation. ? Similarity of CRMs with field samples assures valuable information. ? There is a lack of CRMs for Hg speciation in soils and waters. ? Spiking/fortification procedures must be carefully designed to simulate the behavior of Hg species naturally occurring.
Posted on 18 January 2012 | 2:17 am
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