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Metabolomics, peptidomics and proteomics applications of capillary electrophoresis-mass spectrometry in Foodomics: A review
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Clara Ibáñez , Carolina Simó , Virginia García-Cañas , Alejandro Cifuentes , María Castro-Puyana
In the current post-genomic era, Foodomics has been defined as a discipline that studies food and nutrition through the application of advanced omics approaches. Foodomics involves the use of genomics, transcriptomics, epigenetics, proteomics, peptidomics, and/or metabolomics to investigate food quality, safety, traceability and bioactivity. In this context, capillary electrophoresis-mass spectrometry (CE-MS) has been applied mainly in food proteomics, peptidomics and metabolomics. The aim of this review work is to present an overview of the most recent developments and applications of CE-MS as analytical platform for Foodomics, covering the relevant works published from 2008 to 2012. The review provides also information about the integration of several omics approaches in the new Foodomics field.
Source:Analytica Chimica Acta, Volume 802
Author(s): Clara Ibáñez , Carolina Simó , Virginia García-Cañas , Alejandro Cifuentes , María Castro-Puyana
In the current post-genomic era, Foodomics has been defined as a discipline that studies food and nutrition through the application of advanced omics approaches. Foodomics involves the use of genomics, transcriptomics, epigenetics, proteomics, peptidomics, and/or metabolomics to investigate food quality, safety, traceability and bioactivity. In this context, capillary electrophoresis-mass spectrometry (CE-MS) has been applied mainly in food proteomics, peptidomics and metabolomics. The aim of this review work is to present an overview of the most recent developments and applications of CE-MS as analytical platform for Foodomics, covering the relevant works published from 2008 to 2012. The review provides also information about the integration of several omics approaches in the new Foodomics field.
Graphical abstract
Activated sludge characterization through microscopy: A review on quantitative image analysis and chemometric techniques
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Daniela P. Mesquita , A. Luís Amaral , Eugénio C. Ferreira
In wastewater treatment processes, and particularly in activated sludge systems, efficiency is quite dependent on the operating conditions, and a number of problems may arise due to sludge structure and proliferation of specific microorganisms. In fact, bacterial communities and protozoa identification by microscopy inspection is already routinely employed in a considerable number of cases. Furthermore, quantitative image analysis techniques have been increasingly used throughout the years for the assessment of aggregates and filamentous bacteria properties. These procedures are able to provide an ever growing amount of data for wastewater treatment processes in which chemometric techniques can be a valuable tool. However, the determination of microbial communities’ properties remains a current challenge in spite of the great diversity of microscopy techniques applied. In this review, activated sludge characterization is discussed highlighting the aggregates structure and filamentous bacteria determination by image analysis on bright-field, phase-contrast, and fluorescence microscopy. An in-depth analysis is performed to summarize the many new findings that have been obtained, and future developments for these biological processes are further discussed.
Source:Analytica Chimica Acta, Volume 802
Author(s): Daniela P. Mesquita , A. Luís Amaral , Eugénio C. Ferreira
In wastewater treatment processes, and particularly in activated sludge systems, efficiency is quite dependent on the operating conditions, and a number of problems may arise due to sludge structure and proliferation of specific microorganisms. In fact, bacterial communities and protozoa identification by microscopy inspection is already routinely employed in a considerable number of cases. Furthermore, quantitative image analysis techniques have been increasingly used throughout the years for the assessment of aggregates and filamentous bacteria properties. These procedures are able to provide an ever growing amount of data for wastewater treatment processes in which chemometric techniques can be a valuable tool. However, the determination of microbial communities’ properties remains a current challenge in spite of the great diversity of microscopy techniques applied. In this review, activated sludge characterization is discussed highlighting the aggregates structure and filamentous bacteria determination by image analysis on bright-field, phase-contrast, and fluorescence microscopy. An in-depth analysis is performed to summarize the many new findings that have been obtained, and future developments for these biological processes are further discussed.
Graphical abstract
Handling large datasets of hyperspectral images: Reducing data size without loss of useful information
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Carlotta Ferrari , Giorgia Foca , Alessandro Ulrici
Hyperspectral Imaging (HSI) is gaining increasing interest in the field of analytical chemistry, since this fast and non-destructive technique allows one to easily acquire a large amount of spectral and spatial information on a wide number of samples in very short times. However, the large size of hyperspectral image data often limits the possible uses of this technique, due to the difficulty of evaluating many samples altogether, for example when one needs to consider a representative number of samples for the implementation of on-line applications. In order to solve this problem, we propose a novel chemometric strategy aimed to significantly reduce the dataset size, which allows to analyze in a completely automated way from tens up to hundreds of hyperspectral images altogether, without losing neither spectral nor spatial information. The approach essentially consists in compressing each hyperspectral image into a signal, named hyperspectrogram, which is created by combining several quantities obtained by applying PCA to each single hyperspectral image. Hyperspectrograms can then be used as a compact set of descriptors and subjected to blind analysis techniques. Moreover, a further improvement of both data compression and calibration/classification performances can be achieved by applying proper variable selection methods to the hyperspectrograms. A visual evaluation of the correctness of the choices made by the algorithm can be obtained by representing the selected features back into the original image domain. Likewise, the interpretation of the chemical information underlying the selected regions of the hyperspectrograms related to the loadings is enabled by projecting them in the original spectral domain. Examples of applications of the hyperspectrogram-based approach to hyperspectral images of food samples in the NIR range (1000–1700nm) and in the vis–NIR range (400–1000nm), facing a calibration and a defect detection issue respectively, demonstrate the effectiveness of the proposed approach.
Source:Analytica Chimica Acta, Volume 802
Author(s): Carlotta Ferrari , Giorgia Foca , Alessandro Ulrici
Hyperspectral Imaging (HSI) is gaining increasing interest in the field of analytical chemistry, since this fast and non-destructive technique allows one to easily acquire a large amount of spectral and spatial information on a wide number of samples in very short times. However, the large size of hyperspectral image data often limits the possible uses of this technique, due to the difficulty of evaluating many samples altogether, for example when one needs to consider a representative number of samples for the implementation of on-line applications. In order to solve this problem, we propose a novel chemometric strategy aimed to significantly reduce the dataset size, which allows to analyze in a completely automated way from tens up to hundreds of hyperspectral images altogether, without losing neither spectral nor spatial information. The approach essentially consists in compressing each hyperspectral image into a signal, named hyperspectrogram, which is created by combining several quantities obtained by applying PCA to each single hyperspectral image. Hyperspectrograms can then be used as a compact set of descriptors and subjected to blind analysis techniques. Moreover, a further improvement of both data compression and calibration/classification performances can be achieved by applying proper variable selection methods to the hyperspectrograms. A visual evaluation of the correctness of the choices made by the algorithm can be obtained by representing the selected features back into the original image domain. Likewise, the interpretation of the chemical information underlying the selected regions of the hyperspectrograms related to the loadings is enabled by projecting them in the original spectral domain. Examples of applications of the hyperspectrogram-based approach to hyperspectral images of food samples in the NIR range (1000–1700nm) and in the vis–NIR range (400–1000nm), facing a calibration and a defect detection issue respectively, demonstrate the effectiveness of the proposed approach.
Graphical abstract
Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Manuel Azenha , Eric Schillinger , Esther Sanmartin , M. Teresa Regueiras , Fernando Silva , Börje Sellergren
The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel–titanium (Ni–Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13–15nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography.
Source:Analytica Chimica Acta, Volume 802
Author(s): Manuel Azenha , Eric Schillinger , Esther Sanmartin , M. Teresa Regueiras , Fernando Silva , Börje Sellergren
The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel–titanium (Ni–Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13–15nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography.
Graphical abstract
Molecular evaluation of soil organic matter characteristics in three agricultural soils by improved off-line thermochemolysis: The effect of hydrofluoric acid demineralisation treatment
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Riccardo Spaccini , XiangYun Song , Vincenza Cozzolino , Alessandro Piccolo
The molecular composition of soil organic matter (SOM) in three agricultural fields under different managements, was evaluated by off-line thermochemolysis followed by gas chromatography mass spectrometry analysis (THM-GC-MS). While this technique enabled the characterization of SOM components in coarse textured soil, its efficiency in heavy textured soils was seriously affected by the interference of clay minerals, which catalyzed the formation of secondary artifacts in pyrolysates. Soil demineralization with hydrofluoric acid (HF) solutions effectively improved the reliable characterization of organic compounds in clayey soils by thermochemolysis, while did not alter significantly the results of coarse textured soil. A wide range of lignin monomers and lipids molecules, of plant and microbial origin, were identified in the pyrograms of HF treated soils, thereby revealing interesting molecular differences between SOM management practices. Our results indicated that clay removal provided by HF pretreatment enhanced the capacity of thermochemolysis to be a valuable and accurate technique to study the SOM dynamics also in heavy-textured and OC-depleted cultivated soils.
Source:Analytica Chimica Acta, Volume 802
Author(s): Riccardo Spaccini , XiangYun Song , Vincenza Cozzolino , Alessandro Piccolo
The molecular composition of soil organic matter (SOM) in three agricultural fields under different managements, was evaluated by off-line thermochemolysis followed by gas chromatography mass spectrometry analysis (THM-GC-MS). While this technique enabled the characterization of SOM components in coarse textured soil, its efficiency in heavy textured soils was seriously affected by the interference of clay minerals, which catalyzed the formation of secondary artifacts in pyrolysates. Soil demineralization with hydrofluoric acid (HF) solutions effectively improved the reliable characterization of organic compounds in clayey soils by thermochemolysis, while did not alter significantly the results of coarse textured soil. A wide range of lignin monomers and lipids molecules, of plant and microbial origin, were identified in the pyrograms of HF treated soils, thereby revealing interesting molecular differences between SOM management practices. Our results indicated that clay removal provided by HF pretreatment enhanced the capacity of thermochemolysis to be a valuable and accurate technique to study the SOM dynamics also in heavy-textured and OC-depleted cultivated soils.
Graphical abstract
Steroid and steroid glucuronide profiles in urine during pregnancy determined by liquid chromatography–electrospray ionization-tandem mass spectrometry
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Sirkku E. Jäntti , Minna Hartonen , Mika Hilvo , Heli Nygren , Tuulia Hyötyläinen , Raimo A. Ketola , Risto Kostiainen
An ultra performance liquid chromatography–electrospray ionization-tandem mass spectrometry (UPLC–MS/MS) method was developed for the analysis of steroids and their glucuronides in urine samples. The method provides high sensitivity and fast analysis, as both steroids and their glucuronides can be analyzed directly without hydrolysis or complex sample preparation. The method was applied in profiling of targeted and nontargeted steroids and steroid glucuronides during pregnancy. The concentrations of 11 of 27 targeted steroids and steroid glucuronides and the concentrations of 25 nontargeted steroid glucuronides increased about 10–400 fold during the pregnancy. The concentrations of most of these 36 compounds began to increase in the first days of the pregnancy, increased gradually during the pregnancy, achieved a maximum in late pregnancy, and decreased sharply after delivery. Exceptionally, the concentrations of allopregnanolone and 17-hydroxypregnenolone started to increase later than those of the other steroids. Moreover, the concentrations of E2 glucuronides began to decrease one week before the delivery, in contrast to most of the steroids and steroid glucuronides, whose concentrations dropped sharply during the delivery. Concentrations of 34 compounds decreased noticeably when the subject was on sick leave owing a series of painful contractions. The results suggest that steroids and especially steroid glucuronides may provide a valuable diagnostic tool to follow the course of pregnancy.
Source:Analytica Chimica Acta, Volume 802
Author(s): Sirkku E. Jäntti , Minna Hartonen , Mika Hilvo , Heli Nygren , Tuulia Hyötyläinen , Raimo A. Ketola , Risto Kostiainen
An ultra performance liquid chromatography–electrospray ionization-tandem mass spectrometry (UPLC–MS/MS) method was developed for the analysis of steroids and their glucuronides in urine samples. The method provides high sensitivity and fast analysis, as both steroids and their glucuronides can be analyzed directly without hydrolysis or complex sample preparation. The method was applied in profiling of targeted and nontargeted steroids and steroid glucuronides during pregnancy. The concentrations of 11 of 27 targeted steroids and steroid glucuronides and the concentrations of 25 nontargeted steroid glucuronides increased about 10–400 fold during the pregnancy. The concentrations of most of these 36 compounds began to increase in the first days of the pregnancy, increased gradually during the pregnancy, achieved a maximum in late pregnancy, and decreased sharply after delivery. Exceptionally, the concentrations of allopregnanolone and 17-hydroxypregnenolone started to increase later than those of the other steroids. Moreover, the concentrations of E2 glucuronides began to decrease one week before the delivery, in contrast to most of the steroids and steroid glucuronides, whose concentrations dropped sharply during the delivery. Concentrations of 34 compounds decreased noticeably when the subject was on sick leave owing a series of painful contractions. The results suggest that steroids and especially steroid glucuronides may provide a valuable diagnostic tool to follow the course of pregnancy.
Graphical abstract
An ultrasensitive quantum dots fluorescent polarization immunoassay based on the antibody modified Au nanoparticles amplifying for the detection of adenosine triphosphate
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Yanlong He , Jianniao Tian , Kun Hu , Juanni Zhang , Sheng Chen , Yixuan Jiang , Yanchun Zhao , Shulin Zhao
In this work, an ultrasensitive fluorescent polarization immunoassay (FPIA) method based on the quantum dot/aptamer/antibody/gold nanoparticles ensemble has been developed for the detection of adenosine triphosphate (ATP). DNA hybridization is formed when ATP is present in the PBS solution containing the DNA-conjugated quantum dots (QDs) and antibody-AuNPs. The substantial sensitivity improvement of the antibody-AuNPs-enhanced method is mainly attributed to the slower rotation of fluorescent unit when QDs-labeled oligonucleotides hybridize with antibody modified the gold nanoparticle. As a result, the fluorescent polarization (FP) values of the system increase significantly. Under the optimal conditions, a linear response with ATP concentration is ranged from 8×10−12 M to 2.40×10−4 M. The detection limit reached as low as 1.8pM. The developed work provides a sensitive and selective immunoassay protocol for ATP detection, which could be applied in more bioanalytical systems.
Source:Analytica Chimica Acta, Volume 802
Author(s): Yanlong He , Jianniao Tian , Kun Hu , Juanni Zhang , Sheng Chen , Yixuan Jiang , Yanchun Zhao , Shulin Zhao
In this work, an ultrasensitive fluorescent polarization immunoassay (FPIA) method based on the quantum dot/aptamer/antibody/gold nanoparticles ensemble has been developed for the detection of adenosine triphosphate (ATP). DNA hybridization is formed when ATP is present in the PBS solution containing the DNA-conjugated quantum dots (QDs) and antibody-AuNPs. The substantial sensitivity improvement of the antibody-AuNPs-enhanced method is mainly attributed to the slower rotation of fluorescent unit when QDs-labeled oligonucleotides hybridize with antibody modified the gold nanoparticle. As a result, the fluorescent polarization (FP) values of the system increase significantly. Under the optimal conditions, a linear response with ATP concentration is ranged from 8×10−12 M to 2.40×10−4 M. The detection limit reached as low as 1.8pM. The developed work provides a sensitive and selective immunoassay protocol for ATP detection, which could be applied in more bioanalytical systems.
Graphical abstract
Simultaneous, real-time measurement of nitric oxide and oxygen dynamics during cardiac ischemia–reperfusion of the rat utilizing sol–gel-derived electrochemical microsensors
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Sung Wook Kang , Ok Kyun Kim , Bochan Seo , Sung Ho Lee , Fu Shi Quan , Jae Ho Shin , Gi-Ja Lee , Hun-Kuk Park
In this study, we simultaneously measured nitric oxide (NO) and oxygen (O2) dynamics in the myocardium during myocardial ischemia–reperfusion (IR) utilizing sol–gel modified electrochemical NO and O2 microsensors. In addition, we attempted to clarify the correlation between NO release in the ischemic period and O2 restoration in the myocardium after reperfusion, comparing a control heart with a remote ischemic preconditioning (RIPC)-treated heart as an attractive strategy for myocardial protection. Rat hearts were randomly divided into two groups: a control group (n =5) and an RIPC group (n =5, with RIPC treatment). Myocardia that underwent RIPC treatment (182±70nM, p <0.05) released more NO during the ischemic period than those of the control group (63±41nM). The restoration value of oxygen tension (pO2) in the RIPC group significantly increased and was restored to pre-ischemic levels (92.6±36.8%); however, the pO2 of the control group did not increase throughout the reperfusion period (5.7±7.5%, p =0.001). Myocardial infarct size measurements revealed a significant decrease in cell death in the myocardium region of the RIPC group (41.44±6.42%, p =0.001) compared with the control group (60.05±10.91%). As a result, we showed that the cardioprotective effect of RIPC could be attributed to endogenous NO production during the ischemic period, which subsequently promoted reoxygenation in post-ischemic myocardia during early reperfusion. Our results suggest that the promotion of endogenous formation during an ischemic episode might be helpful as a therapeutic strategy for protecting the myocardium from IR injury. Additionally, our NO and O2 perm-selective microsensors could be utilized to evaluate the effect of drug or treatment.
Source:Analytica Chimica Acta, Volume 802
Author(s): Sung Wook Kang , Ok Kyun Kim , Bochan Seo , Sung Ho Lee , Fu Shi Quan , Jae Ho Shin , Gi-Ja Lee , Hun-Kuk Park
In this study, we simultaneously measured nitric oxide (NO) and oxygen (O2) dynamics in the myocardium during myocardial ischemia–reperfusion (IR) utilizing sol–gel modified electrochemical NO and O2 microsensors. In addition, we attempted to clarify the correlation between NO release in the ischemic period and O2 restoration in the myocardium after reperfusion, comparing a control heart with a remote ischemic preconditioning (RIPC)-treated heart as an attractive strategy for myocardial protection. Rat hearts were randomly divided into two groups: a control group (n =5) and an RIPC group (n =5, with RIPC treatment). Myocardia that underwent RIPC treatment (182±70nM, p <0.05) released more NO during the ischemic period than those of the control group (63±41nM). The restoration value of oxygen tension (pO2) in the RIPC group significantly increased and was restored to pre-ischemic levels (92.6±36.8%); however, the pO2 of the control group did not increase throughout the reperfusion period (5.7±7.5%, p =0.001). Myocardial infarct size measurements revealed a significant decrease in cell death in the myocardium region of the RIPC group (41.44±6.42%, p =0.001) compared with the control group (60.05±10.91%). As a result, we showed that the cardioprotective effect of RIPC could be attributed to endogenous NO production during the ischemic period, which subsequently promoted reoxygenation in post-ischemic myocardia during early reperfusion. Our results suggest that the promotion of endogenous formation during an ischemic episode might be helpful as a therapeutic strategy for protecting the myocardium from IR injury. Additionally, our NO and O2 perm-selective microsensors could be utilized to evaluate the effect of drug or treatment.
Graphical abstract
An ultrasensitive method for the determination of melamine using cadmium telluride quantum dots as fluorescence probes
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Xiafei Li , Jin Li , Huiyan Kuang , Lei Feng , Shoujun Yi , Xiaodong Xia , Haowen Huang , Yong Chen , Chunran Tang , Yunlong Zeng
An ultrasensitive and simple method for the determination of melamine was developed based on the fluorescence quenching of thioglycolic acid (TGA) capped CdTe quantum dots (QDs) at pH 11.0. In strong alkaline aqueous solution, the selectivity of the method has been greatly improved due to most heavy metal ions show no interference as they are in the precipitation form or in their anion form. Furthermore, CdTe quantum dots have higher quantum yields at higher pH. The method has a wider concentration range and lower detection limit. The influence factors on the determination of melamine were investigated and the optimum conditions were determined. Under optimum conditions, the fluorescence intensity change of TGA coated CdTe quantum dots was linearly proportional to melamine over a concentration range from 1.0×10−11 to 1.0×10−5 molL−1 with a correlation coefficient of 0.9943 and a detection limit of 5×10−12 molL−1. The mechanism of fluorescence quenching of the QDs has been proposed based on the infrared spectroscopy information and electrophoresis experiments in presence of melamine under alkaline condition. The proposed method was employed to detect trace melamine in milk powder and pet feeds with satisfactory results.
Source:Analytica Chimica Acta, Volume 802
Author(s): Xiafei Li , Jin Li , Huiyan Kuang , Lei Feng , Shoujun Yi , Xiaodong Xia , Haowen Huang , Yong Chen , Chunran Tang , Yunlong Zeng
An ultrasensitive and simple method for the determination of melamine was developed based on the fluorescence quenching of thioglycolic acid (TGA) capped CdTe quantum dots (QDs) at pH 11.0. In strong alkaline aqueous solution, the selectivity of the method has been greatly improved due to most heavy metal ions show no interference as they are in the precipitation form or in their anion form. Furthermore, CdTe quantum dots have higher quantum yields at higher pH. The method has a wider concentration range and lower detection limit. The influence factors on the determination of melamine were investigated and the optimum conditions were determined. Under optimum conditions, the fluorescence intensity change of TGA coated CdTe quantum dots was linearly proportional to melamine over a concentration range from 1.0×10−11 to 1.0×10−5 molL−1 with a correlation coefficient of 0.9943 and a detection limit of 5×10−12 molL−1. The mechanism of fluorescence quenching of the QDs has been proposed based on the infrared spectroscopy information and electrophoresis experiments in presence of melamine under alkaline condition. The proposed method was employed to detect trace melamine in milk powder and pet feeds with satisfactory results.
Graphical abstract
Inkjet printing lanthanide doped nanorods test paper for visual assays of nitroaromatic explosives
31 October 2013,
13:29:59
Publication date: 13 November
2013
Source:Analytica Chimica Acta, Volume 802
Author(s): Liang Hong , Qingsong Mei , Lei Yang , Cheng Zhang , Renyong Liu , Mingyong Han , Ruilong Zhang , Zhongping Zhang
The facile and sensitive strategies for detections of nitroaromatic explosives are highly desirable in many challenging environments, especially for homeland security against terrorism. Here, we inkjet printed polyethylenimine (PEI)-coated Ce, Tb co-doped NaGdF4 nanorods (NaGdF4:Ce/Tb NRs) onto common filter paper to construct test paper for visual and instant detections of a typical explosive 2,4,6-trinitrophenol (TNP). Polyethylenimine molecules not only facilitate the formation of uniform NaGdF4 nanorods but also provide specific recognized sites for TNP by the acid–base pairing interaction. The resultant TNP bound at the surface of PEI-coated NaGdF4:Ce/Tb NRs can strongly quench the phosphorescence with a remarkably high quenching constant by the charge transfer mechanism from NaGdF4:Ce/Tb NRs to TNP. By printing of the probe on a piece of filter paper, trace amounts of TNP can be visually detected by the appearance of a dark color against a bright green background under a UV lamp. This test paper can detect TNP as low as 0.45ngmm−2 by the naked eye, which provides a potential application in the rapid, on-line detections of explosives.
Source:Analytica Chimica Acta, Volume 802
Author(s): Liang Hong , Qingsong Mei , Lei Yang , Cheng Zhang , Renyong Liu , Mingyong Han , Ruilong Zhang , Zhongping Zhang
The facile and sensitive strategies for detections of nitroaromatic explosives are highly desirable in many challenging environments, especially for homeland security against terrorism. Here, we inkjet printed polyethylenimine (PEI)-coated Ce, Tb co-doped NaGdF4 nanorods (NaGdF4:Ce/Tb NRs) onto common filter paper to construct test paper for visual and instant detections of a typical explosive 2,4,6-trinitrophenol (TNP). Polyethylenimine molecules not only facilitate the formation of uniform NaGdF4 nanorods but also provide specific recognized sites for TNP by the acid–base pairing interaction. The resultant TNP bound at the surface of PEI-coated NaGdF4:Ce/Tb NRs can strongly quench the phosphorescence with a remarkably high quenching constant by the charge transfer mechanism from NaGdF4:Ce/Tb NRs to TNP. By printing of the probe on a piece of filter paper, trace amounts of TNP can be visually detected by the appearance of a dark color against a bright green background under a UV lamp. This test paper can detect TNP as low as 0.45ngmm−2 by the naked eye, which provides a potential application in the rapid, on-line detections of explosives.
Graphical abstract
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