Selected papers from the latest issue:
Electrochemical stripping analysis of nanogold label-induced silver deposition for ultrasensitive multiplexed detection of tumor markers13 March 2012, 10:07:06
Publication year: 2012
Source:Analytica Chimica Acta, Volume 721
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 α-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 3.9pgmL−1, 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.
Source:Analytica Chimica Acta, Volume 721
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 α-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 3.9pgmL−1, 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.
Graphical Abstract
Graphical abstract Highlights
► 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.Probing protein interactions with hydrogen/deuterium exchange and mass spectrometry—A review
13 March 2012, 10:07:06
Publication year: 2012
Source:Analytica Chimica Acta, Volume 721
Andrew J. Percy, Martial Rey, Kyle M. 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.
Source:Analytica Chimica Acta, Volume 721
Andrew J. Percy, Martial Rey, Kyle M. 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.
Graphical Abstract
Graphical abstract Highlights
► Protein chemistry generates mass shifts useful for structure–function studies. ► H/DX supports a powerful mass shift method for protein interaction analysis. ► H/DX mass shifts are useful for determining binding data (K d, off-rates). ► Improved H/DX–MS workflows can accommodate complex protein systems.Speciation of mercury in fish samples by flow injection catalytic cold vapour atomic absorption spectrometry
13 March 2012, 10:07:06
Publication year: 2012
Source:Analytica Chimica Acta, Volume 721
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 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 CHg 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 91.5% and 102.3% recoveries for total and methyl mercury, respectively. The use of flow injection enabled rapid analysis with a sample throughput of 180h−1.
Source:Analytica Chimica Acta, Volume 721
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 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 CHg 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 91.5% and 102.3% recoveries for total and methyl mercury, respectively. The use of flow injection enabled rapid analysis with a sample throughput of 180h−1.
Graphical Abstract
Graphical abstract Highlights
► Successful speciation of inorganic and organic Hg with Fe3+, Cu2+ and thiourea as catalysts. ► Best sensitivity enhancement and similar sensitivity for MeHg and Hg2+ with Fe3+. ► Successful use of Hg2+ as the primary standard for quantification of inorganic and total-Hg. ► Quantitative extraction of Hg and MeHg with 2M HCl which contained thiourea. ► Integration with FIA for rapid analysis with a sample throughput of 180h−1.A new formulation to estimate the variance of model prediction. Application to near infrared spectroscopy calibration
13 March 2012, 10:07:06
Publication year: 2012
Source:Analytica Chimica Acta, Volume 721
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.
Source:Analytica Chimica Acta, Volume 721
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.
Graphical Abstract
Graphical abstract Highlights
► 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.Potential antioxidant compounds in Mallotus species fingerprints. Part II: Fingerprint alignment, data analysis and peak identification
13 March 2012, 10:07:06
Publication year: 2012
Source:Analytica Chimica Acta, Volume 721
C. Tistaert, B. Dejaegher, G. Chataigné, C. Rivière, N. Nguyen Hoai, M. Chau Van, J. Quetin-Leclercq, Y. Vander Heyden
Some Mallotus species are commonly used as 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 39 Mallotus samples (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 given Mallotus species, 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 the Mallotus fingerprints 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–mass spectrometry (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 were also considered.
Source:Analytica Chimica Acta, Volume 721
C. Tistaert, B. Dejaegher, G. Chataigné, C. Rivière, N. Nguyen Hoai, M. Chau Van, J. Quetin-Leclercq, Y. Vander Heyden
Some Mallotus species are commonly used as 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 39 Mallotus samples (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 given Mallotus species, 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 the Mallotus fingerprints 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–mass spectrometry (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 were also considered.
Graphical Abstract
Graphical abstract Highlights
► Indication of peaks responsible for the antioxidant activity of Mallotus species (O-PLS). ► Development of a warping strategy based on correlation optimised warping. ► Evaluation of a multivariate model prior and after alignment for indicative and predictive purposes. ► LC–MS analyses of the indicated peaks.Fractions of Rechtschaffner matrices as supersaturated designs in screening experiments aimed at evaluating main and two-factor interaction effects
13 March 2012, 10:07:06
Publication year: 2012
Source:Analytica Chimica Acta, Volume 721
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.
Source:Analytica Chimica Acta, Volume 721
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.
Graphical Abstract
Graphical abstract Highlights
► 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.Simultaneous electrochemical sensing of ascorbic acid, dopamine and uric acid at anodized nanocrystalline graphite-like pyrolytic carbon film electrode
13 March 2012, 10:07:06
Publication year: 2012
Source:Analytica Chimica Acta, Volume 721
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 2.9μM for AA, 0.04μM for DA, and 0.03μM for UA with sensitivities of 0.078, 5.345, and 6.192AM−1, 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.
Source:Analytica Chimica Acta, Volume 721
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 2.9μM for AA, 0.04μM for DA, and 0.03μM for UA with sensitivities of 0.078, 5.345, and 6.192AM−1, 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.
Graphical Abstract
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