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Determination of trace elements in lithium niobate crystals by solid sampling and solution-based spectrometry methods
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
László Bencs, Krisztina György, Márta Kardos, János Osán, Bálint Alföldy, Imre Varga, Zsolt Ajtony, Norbert Szoboszlai, Zsolt Stefánka, Éva Széles, László Kovács
Solid sampling (SS) graphite furnace atomic absorption spectrometry (GFAAS) and solution-based (SB) methods of GFAAS, flame atomic absorption spectrometry (FAAS), inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) were elaborated and/or optimized for the determination of Cr, Fe and Mn trace elements used as dopants in lithium niobate optical crystals. The calibration of the SS-GFAAS analysis was possible with the application of the three-point-estimation standard addition method, while the SB methods were mostly calibrated against matrix-matched and/or acidic standards. Spectral and non-spectral interferences were studied in SB-GFAAS after digestion of the samples. The SS-GFAAS method required the use of less sensitive spectral lines of the analytes and a higher internal furnace gas (Ar) flow rate to decrease the sensitivity for crystal samples of higher (doped) analyte content. The chemical forms of the matrix produced at various stages of the graphite furnace heating cycle, dispensed either as a solid sample or a solution (after digestion), were studied by means of the X-ray near-edge absorption structure (XANES). These results revealed that the solid matrix vaporized/deposited in the graphite furnace is mostly present in the metallic form, while the dry residue from the solution form mostly vaporized/deposited as the oxide of niobium.
Source:Analytica Chimica Acta, Volume 726
László Bencs, Krisztina György, Márta Kardos, János Osán, Bálint Alföldy, Imre Varga, Zsolt Ajtony, Norbert Szoboszlai, Zsolt Stefánka, Éva Széles, László Kovács
Solid sampling (SS) graphite furnace atomic absorption spectrometry (GFAAS) and solution-based (SB) methods of GFAAS, flame atomic absorption spectrometry (FAAS), inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) were elaborated and/or optimized for the determination of Cr, Fe and Mn trace elements used as dopants in lithium niobate optical crystals. The calibration of the SS-GFAAS analysis was possible with the application of the three-point-estimation standard addition method, while the SB methods were mostly calibrated against matrix-matched and/or acidic standards. Spectral and non-spectral interferences were studied in SB-GFAAS after digestion of the samples. The SS-GFAAS method required the use of less sensitive spectral lines of the analytes and a higher internal furnace gas (Ar) flow rate to decrease the sensitivity for crystal samples of higher (doped) analyte content. The chemical forms of the matrix produced at various stages of the graphite furnace heating cycle, dispensed either as a solid sample or a solution (after digestion), were studied by means of the X-ray near-edge absorption structure (XANES). These results revealed that the solid matrix vaporized/deposited in the graphite furnace is mostly present in the metallic form, while the dry residue from the solution form mostly vaporized/deposited as the oxide of niobium.
Graphical Abstract
Graphical abstract Highlights
► Solid sampling GFAAS was studied for Cr, Fe and Mn determination in lithium niobate. ► Solution based GFAAS, FAAS, ICP-OES and ICP-MS were elaborated for method validation. ► The performances of the elaborated spectrochemical methods have been compared. ► The chemical forms of the matrix produced in GFAAS cycles were studied by XANES.Alignment and clustering strategies for GC×GC–MS features using a cylindrical mapping
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Jos J.A.M. Weusten, Eduard P.P.A. Derks, John H.M. Mommers, Sjoerd van der Wal
Comprehensive two-dimensional gas chromatography coupled to mass spectrometry is a powerful tool to analyze complex samples. For application of the technique in studies like biomarker discovery in which large sets of complex samples have to be analyzed, extensive preprocessing is needed to align the data obtained in several injections (analyses). We developed new alignment and clustering algorithms for this type of data. New in the current procedures is the consistent way in which the phenomenon referred to as wrap-around is treated. The data analysis problems associated with this phenomenon are solved by treating the 2D display as the surface of a three-dimensional cylinder. Based on this transformation we developed a new similarity metric for features as a function of both the cylindrical distance (reflecting similarity in chromatographic behavior) and of the mass spectral correlation (reflecting similarity in chemical structure). The concepts are used in warping and clustering, and include a protection against greedy warping. The methods were applied – for the purpose of an example – to the analysis of 11 replicates of a human urine sample concentrated by solid phase extraction. It is shown that the alignment is well protected against greedy warping which is important with respect to analytical qualities as robustness and repeatability. It is also demonstrated that chemically similar features are clustered together. The paper is organized as follows. First a brief introduction is provided addressing the background of the GC×GC–MS data structure followed by a theoretical section with a conceptual description of the procedures and details of the algorithms. Finally an example is given in the experimental section, illustrating the application of the procedures.
Source:Analytica Chimica Acta, Volume 726
Jos J.A.M. Weusten, Eduard P.P.A. Derks, John H.M. Mommers, Sjoerd van der Wal
Comprehensive two-dimensional gas chromatography coupled to mass spectrometry is a powerful tool to analyze complex samples. For application of the technique in studies like biomarker discovery in which large sets of complex samples have to be analyzed, extensive preprocessing is needed to align the data obtained in several injections (analyses). We developed new alignment and clustering algorithms for this type of data. New in the current procedures is the consistent way in which the phenomenon referred to as wrap-around is treated. The data analysis problems associated with this phenomenon are solved by treating the 2D display as the surface of a three-dimensional cylinder. Based on this transformation we developed a new similarity metric for features as a function of both the cylindrical distance (reflecting similarity in chromatographic behavior) and of the mass spectral correlation (reflecting similarity in chemical structure). The concepts are used in warping and clustering, and include a protection against greedy warping. The methods were applied – for the purpose of an example – to the analysis of 11 replicates of a human urine sample concentrated by solid phase extraction. It is shown that the alignment is well protected against greedy warping which is important with respect to analytical qualities as robustness and repeatability. It is also demonstrated that chemically similar features are clustered together. The paper is organized as follows. First a brief introduction is provided addressing the background of the GC×GC–MS data structure followed by a theoretical section with a conceptual description of the procedures and details of the algorithms. Finally an example is given in the experimental section, illustrating the application of the procedures.
Graphical Abstract
Graphical abstract Highlights
► Data preprocessing is an important but complex step for analysis of GC×GC–MS data. ► We developed a strategy to deal with the phenomenon known as wrap-around. ► We developed a similarity measure for features based on GC×GC and MS information. ► We developed a concept to identify non-specific features. ► We developed an alignment procedure based on cluster analysis.A layered magnetic iron/iron oxide nanoscavenger for the analytical enrichment of ng-L−1 concentration levels of heavy metals from water
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Andreas E. Karatapanis, Dimitrios E. Petrakis, Constantine D. Stalikas
Magnetically driven separation techniques have received considerable attention in recent decade because of their great potential application. In this study, we investigate the application of an unmodified layered magnetic Fe/Fe2O3 nanoscavenger for the analytical enrichment and determination of sub-parts per billion concentrations of Cd(II), Pb(II), Ni(II), Cr(VI) and As(V) from water samples. The synthesized nanoscavenger was characterized by BET, TGA, XRD and IR and the parameters influencing the extraction and recovery of the preconcentration process were assessed by atomic absorption spectrometry. The possible mechanism of the enrichment of heavy metals on Fe/Fe2O3 was proposed, which involved the dominant adsorption and reduction. The nanoscale size offers large surface area and high reactivity of sorption and reduction reactions. The obtained limits of detection for the metals studied were in the range of 20–125ngL−1 and the applicability of the nanomaterial was verified using a real sample matrix. The method is environmentally friendly as only 15mg of nanoscavenger are used, no organic solvent is required for the extraction and the experiment is performed without the need for filtration or preparation of packed preconcentration columns.
Source:Analytica Chimica Acta, Volume 726
Andreas E. Karatapanis, Dimitrios E. Petrakis, Constantine D. Stalikas
Magnetically driven separation techniques have received considerable attention in recent decade because of their great potential application. In this study, we investigate the application of an unmodified layered magnetic Fe/Fe2O3 nanoscavenger for the analytical enrichment and determination of sub-parts per billion concentrations of Cd(II), Pb(II), Ni(II), Cr(VI) and As(V) from water samples. The synthesized nanoscavenger was characterized by BET, TGA, XRD and IR and the parameters influencing the extraction and recovery of the preconcentration process were assessed by atomic absorption spectrometry. The possible mechanism of the enrichment of heavy metals on Fe/Fe2O3 was proposed, which involved the dominant adsorption and reduction. The nanoscale size offers large surface area and high reactivity of sorption and reduction reactions. The obtained limits of detection for the metals studied were in the range of 20–125ngL−1 and the applicability of the nanomaterial was verified using a real sample matrix. The method is environmentally friendly as only 15mg of nanoscavenger are used, no organic solvent is required for the extraction and the experiment is performed without the need for filtration or preparation of packed preconcentration columns.
Graphical Abstract
Graphical abstract Highlights
► A layered magnetic Fe/Fe2O3 nanomaterial is prepared. ► Analytical enrichment of selected heavy metals on Fe/Fe2O3 nanoparticles. ► The mechanism of enrichment involves the adsorption and reduction. ► The applicability of the nanomaterial is verified using a real sample matrix.Determination of perfluorocarboxylic acids in water by ion-pair dispersive liquid–liquid microextraction and gas chromatography–tandem mass spectrometry with injection port derivatization
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Wen-Lin Liu, Yen-Chen Ko, Bao-Huey Hwang, Zu-Guang Li, Thomas Ching-Cherng Yang, Maw-Rong Lee
A novel technique for derivatization in a gas chromatograph injection port after a one-step extraction of trace perfluorocarboxylic acids (PFCAs) in water with ion pair formation during dispersive liquid–liquid microextraction (DLLME) was investigated. Tetrabutylammonium hydrogen sulfate (TBAHS) was used as the ion pair reagent. PFCA butyl ester derivatives were formed in the GC injection port and then analyzed using gas chromatography coupled to tandem mass spectrometry with negative chemical ionization. According to our analysis, the operative linear range for PFCA detection from 250pgmL−1 to 2μgmL−1 with a relative standard derivation (RSD) below 13%. Detection limits were achieved at the level of 37–51pgmL−1. This method was successfully applied for the analyzing of PFCAs in river water samples from urban and industrial areas without tedious pretreatment. The concentration range over which PFCAs were detected is from 0.6ngmL−1 to 604.9ngmL−1.
Source:Analytica Chimica Acta, Volume 726
Wen-Lin Liu, Yen-Chen Ko, Bao-Huey Hwang, Zu-Guang Li, Thomas Ching-Cherng Yang, Maw-Rong Lee
A novel technique for derivatization in a gas chromatograph injection port after a one-step extraction of trace perfluorocarboxylic acids (PFCAs) in water with ion pair formation during dispersive liquid–liquid microextraction (DLLME) was investigated. Tetrabutylammonium hydrogen sulfate (TBAHS) was used as the ion pair reagent. PFCA butyl ester derivatives were formed in the GC injection port and then analyzed using gas chromatography coupled to tandem mass spectrometry with negative chemical ionization. According to our analysis, the operative linear range for PFCA detection from 250pgmL−1 to 2μgmL−1 with a relative standard derivation (RSD) below 13%. Detection limits were achieved at the level of 37–51pgmL−1. This method was successfully applied for the analyzing of PFCAs in river water samples from urban and industrial areas without tedious pretreatment. The concentration range over which PFCAs were detected is from 0.6ngmL−1 to 604.9ngmL−1.
Graphical Abstract
Graphical abstract Highlights
► One-step extraction of perfluorocarboxylic acids in aqueous was investigated. ► Quantitation was performed by using GC–NCI-MS/MS. ► The detection limits were picogram per milliliter level for all PFCAs analyses.Incorporation of methamphetamine and amphetamine in human hair following controlled oral methamphetamine administration
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Aldo Polettini, Edward J. Cone, David A. Gorelick, Marilyn A. Huestis
Background Although 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 methods Seven volunteers with a history of stimulant use received 4×10mg (low) doses of sustained release S-(+)-MAMP HCl within 1 week, with weekly head hair samples collected by shaving. 3 weeks later, 4 of them received 4×20mg (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, 0.005ngmg−1). Results MAMP T max occurred from 1 to 2 weeks after both doses, with C max ranging from 0.6 to 3.5ngmg−1 after the low and 1.2 to 5.3ngmg−1 after the high MAMP doses. AMP C max in hair was 0.1–0.3ngmg−1 and 0.2–0.5ngmg−1, respectively, for low and high doses. Highly dose-related concentrations within subjects, but large variability between subjects were observed. MAMP concentrations were above the 0.2ngmg−1 cut-off for at least 2 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 2 =0.90, p =0.00) and AMP (r 2 =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 C max and melanin. Conclusions This 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.
Source:Analytica Chimica Acta, Volume 726
Aldo Polettini, Edward J. Cone, David A. Gorelick, Marilyn A. Huestis
Background Although 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 methods Seven volunteers with a history of stimulant use received 4×10mg (low) doses of sustained release S-(+)-MAMP HCl within 1 week, with weekly head hair samples collected by shaving. 3 weeks later, 4 of them received 4×20mg (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, 0.005ngmg−1). Results MAMP T max occurred from 1 to 2 weeks after both doses, with C max ranging from 0.6 to 3.5ngmg−1 after the low and 1.2 to 5.3ngmg−1 after the high MAMP doses. AMP C max in hair was 0.1–0.3ngmg−1 and 0.2–0.5ngmg−1, respectively, for low and high doses. Highly dose-related concentrations within subjects, but large variability between subjects were observed. MAMP concentrations were above the 0.2ngmg−1 cut-off for at least 2 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 2 =0.90, p =0.00) and AMP (r 2 =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 C max and melanin. Conclusions This 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.
Graphical Abstract
Graphical abstract Highlights
► We studied in vivo incorporation of methamphetamine in human head hair. ► Methamphetamine (40 and 80mg) 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 cut-off are proposed.2-Aminopurine hairpin probes for the detection of ultraviolet-induced DNA damage
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Amira F. El-Yazbi, Glen R. Loppnow
Nucleic acid exposure to radiation and chemical insults leads to damage and disease. Thus, detection and understanding DNA damage is important for elucidating molecular mechanisms of disease. However, current methods of DNA damage detection are either time-consuming, destroy the sample, or are too specific to be used for generic detection of damage. In this paper, we develop a fluorescence sensor of 2-aminopurine (2AP), a fluorescent analogue of adenine, incorporated in the loop of a hairpin probe for the quantification of ultraviolet (UV) C-induced nucleic acid damage. Our results show that the selectivity of the 2AP hairpin probe to UV-induced nucleic acid damage is comparable to molecular beacon (MB) probes of DNA damage. The calibration curve for the 2AP hairpin probe shows good linearity (R 2 =0.98) with a limit of detection of 17.2nM. This probe is a simple, fast and economic fluorescence sensor for the quantification of UV-induced damage in DNA.
Source:Analytica Chimica Acta, Volume 726
Amira F. El-Yazbi, Glen R. Loppnow
Nucleic acid exposure to radiation and chemical insults leads to damage and disease. Thus, detection and understanding DNA damage is important for elucidating molecular mechanisms of disease. However, current methods of DNA damage detection are either time-consuming, destroy the sample, or are too specific to be used for generic detection of damage. In this paper, we develop a fluorescence sensor of 2-aminopurine (2AP), a fluorescent analogue of adenine, incorporated in the loop of a hairpin probe for the quantification of ultraviolet (UV) C-induced nucleic acid damage. Our results show that the selectivity of the 2AP hairpin probe to UV-induced nucleic acid damage is comparable to molecular beacon (MB) probes of DNA damage. The calibration curve for the 2AP hairpin probe shows good linearity (R 2 =0.98) with a limit of detection of 17.2nM. This probe is a simple, fast and economic fluorescence sensor for the quantification of UV-induced damage in DNA.
Graphical Abstract
Graphical abstract Highlights
► Molecular beacon with 2AP bases detects DNA damage in a simple mix-and-read assay. ► Molecular beacons with 2AP bases detect damage at a 17.2nM limit of detection. ► The 2AP molecular beacon is linear over a 0–3.5μM concentration range for damage.Improving the efficiency of ion mobility spectrometry analyses by using multivariate calibration
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
David Zamora, Marcelo Blanco
The simplicity, sensitivity and expeditiousness of ion mobility spectrometry (IMS) make it especially useful for the determination of active principal ingredients (APIs) present at low concentrations in pharmaceuticals. However, the poor resolution of this technique precludes the identification and/or determination of substances with similar molecular weights, which exhibit also similar drift times and give overlapped peaks as a result. Oral contraceptives are pharmaceutical formulations containing two APIs of similar molecular weights at very low concentrations which therefore give strongly overlapped peaks hindering their determination by IMS. In this work, we assessed the potential of IMS for detecting and quantifying the contraceptives ethinylestradiol (ETE) and desogestrel (DES) in commercial tablets. To this end, we used various chemometric techniques including a second-derivative (TN2D) algorithm and the more powerful choice Multivariate Curve Resolution (MCR) to improve the resolution of IMS and enable the determination of both APIs. Quantitation was based on PLS1 models for each API. The models constructed involve a single PLS factor with a Y-explained variance above 98.4%, obtaining a RMSEP of 0.34 and 0.63 for ETE and DES, respectively. The ensuing method, which was validated for use in routine analyses, is quite expeditious (analyses take less than 1min) and uses very small amounts of sample (a few microliters). Based on the results, IMS has a great potential for the qualitative and quantitative determination of APIs in low doses.
Source:Analytica Chimica Acta, Volume 726
David Zamora, Marcelo Blanco
The simplicity, sensitivity and expeditiousness of ion mobility spectrometry (IMS) make it especially useful for the determination of active principal ingredients (APIs) present at low concentrations in pharmaceuticals. However, the poor resolution of this technique precludes the identification and/or determination of substances with similar molecular weights, which exhibit also similar drift times and give overlapped peaks as a result. Oral contraceptives are pharmaceutical formulations containing two APIs of similar molecular weights at very low concentrations which therefore give strongly overlapped peaks hindering their determination by IMS. In this work, we assessed the potential of IMS for detecting and quantifying the contraceptives ethinylestradiol (ETE) and desogestrel (DES) in commercial tablets. To this end, we used various chemometric techniques including a second-derivative (TN2D) algorithm and the more powerful choice Multivariate Curve Resolution (MCR) to improve the resolution of IMS and enable the determination of both APIs. Quantitation was based on PLS1 models for each API. The models constructed involve a single PLS factor with a Y-explained variance above 98.4%, obtaining a RMSEP of 0.34 and 0.63 for ETE and DES, respectively. The ensuing method, which was validated for use in routine analyses, is quite expeditious (analyses take less than 1min) and uses very small amounts of sample (a few microliters). Based on the results, IMS has a great potential for the qualitative and quantitative determination of APIs in low doses.
Graphical Abstract
Graphical abstract Highlights
► Simple, inexpensive and highly expeditious method for contraceptives determination. ► Chemometric techniques were assessed to improve efficiency in overlapped peaks. ► TN2D and MCR algorithms enable identification of the two analytes. ► PLS calibration allows APIs to be determined and overcomes their mutual interference.Rapid prediction of moisture content of dehydrated prawns using online hyperspectral imaging system
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Di Wu, Hui Shi, Songjing Wang, Yong He, Yidan Bao, Kangsheng Liu
Because the shape of prawn is not round, spectroscopy instruments cannot measure the spectra of the whole prawn without containing background information. In this study, an online hyperspectral imaging system in the spectral region of 380–1100nm was developed to determine the moisture content of prawns at different dehydrated levels. Hyperspectral images of prawns were acquired at different dehydration periods. The spectra of prawns then were extracted from hyperspectral images based on ‘Manual Prawn Mask’ and ‘Automatic Prawn Mask’, respectively. Spectral data were analyzed using partial least squares regression (PLSR) and least-squares support vector machines (LS-SVM) to establish the calibration models, respectively. Successive projections algorithm (SPA) was first applied for the optimal wavelength selection in the hyperspectral image analysis. Out of 482 wavelengths, only twelve wavelengths (428, 445, 544, 569, 629, 672, 697, 760, 827, 917, 958, and 999nm) were selected by SPA as the optimum wavelengths for moisture prediction. Based on these optimum wavelengths, a multiple linear regression (MLR) calibration model was established and used to obtain the moisture distribution of each prawn. The overall results of this study revealed the potentiality of hyperspectral imaging as an objective and non-destructive method to obtain the content and distribution of moisture of prawns whose shapes are not round.
Source:Analytica Chimica Acta, Volume 726
Di Wu, Hui Shi, Songjing Wang, Yong He, Yidan Bao, Kangsheng Liu
Because the shape of prawn is not round, spectroscopy instruments cannot measure the spectra of the whole prawn without containing background information. In this study, an online hyperspectral imaging system in the spectral region of 380–1100nm was developed to determine the moisture content of prawns at different dehydrated levels. Hyperspectral images of prawns were acquired at different dehydration periods. The spectra of prawns then were extracted from hyperspectral images based on ‘Manual Prawn Mask’ and ‘Automatic Prawn Mask’, respectively. Spectral data were analyzed using partial least squares regression (PLSR) and least-squares support vector machines (LS-SVM) to establish the calibration models, respectively. Successive projections algorithm (SPA) was first applied for the optimal wavelength selection in the hyperspectral image analysis. Out of 482 wavelengths, only twelve wavelengths (428, 445, 544, 569, 629, 672, 697, 760, 827, 917, 958, and 999nm) were selected by SPA as the optimum wavelengths for moisture prediction. Based on these optimum wavelengths, a multiple linear regression (MLR) calibration model was established and used to obtain the moisture distribution of each prawn. The overall results of this study revealed the potentiality of hyperspectral imaging as an objective and non-destructive method to obtain the content and distribution of moisture of prawns whose shapes are not round.
Graphical Abstract
Graphical abstract Highlights
► Hyperspectral imaging as moisture content predictors of prawn. ► Prawns were extracted from background using spatial features of hyperspectral imaging. ► Moisture contents were determined using spectral features of hyperspectral imaging. ► SPA was first used for wavelength selection in hyperspectral imaging analysis. ► Moisture content distributions were visualized at different dehydration periods.3,4,9,10-Perylenetetracarboxylic dianhydride functionalized graphene sheet as labels for ultrasensitive electrochemiluminescent detection of thrombin
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Xianxue Gan, Ruo Yuan, Yaqin Chai, Yali Yuan, Yaling Cao, Yuhong Liao, Huijing Liu
A novel tracer, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) functionalized graphene sheet (GS) composite (GS–TCDA), is employed to label the secondary anti-thrombin aptamer (TBA) to construct an ultrasensitive electrochemiluminescent sandwich-type aptasensor. The GS provided large surface area for loading abundant PTCDA and TBA with good stability and biocompatibility. Because of the excellent electroconductivity of GS and the desirable optical properties of PTCDA, the as-formed Apt II bioconjugate considerably amplified the electrochmiluminescence (ECL) signal of peroxydisulfate (S2O8 2−) and worked as the desirable label for Apt II. On the basis of the considerably amplified ECL signal and sandwich format, an extremely wide range from 1fM to 1nM with an ultralow detection limit of 0.33fM for thrombin was obtained. Additionally, the selectivity and stability of the proposed aptasensor were also excellent. Thus, this procedure has great promise for detection of thrombin present at ultra-trace levels during early stage of diseases.
Source:Analytica Chimica Acta, Volume 726
Xianxue Gan, Ruo Yuan, Yaqin Chai, Yali Yuan, Yaling Cao, Yuhong Liao, Huijing Liu
A novel tracer, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) functionalized graphene sheet (GS) composite (GS–TCDA), is employed to label the secondary anti-thrombin aptamer (TBA) to construct an ultrasensitive electrochemiluminescent sandwich-type aptasensor. The GS provided large surface area for loading abundant PTCDA and TBA with good stability and biocompatibility. Because of the excellent electroconductivity of GS and the desirable optical properties of PTCDA, the as-formed Apt II bioconjugate considerably amplified the electrochmiluminescence (ECL) signal of peroxydisulfate (S2O8 2−) and worked as the desirable label for Apt II. On the basis of the considerably amplified ECL signal and sandwich format, an extremely wide range from 1fM to 1nM with an ultralow detection limit of 0.33fM for thrombin was obtained. Additionally, the selectivity and stability of the proposed aptasensor were also excellent. Thus, this procedure has great promise for detection of thrombin present at ultra-trace levels during early stage of diseases.
Graphical Abstract
Graphical abstract Highlights
► We constructed a novel sandwich-type ECL aptasensor with 3,4,9,10-perylenetetracarboxylic dianhydride functionalized graphene sheet composite (GS–TCDA) for secondary anti-thrombin aptamer (TBA 2) labeling. ► The GS provided large surface area for loading abundant PTCDA and TBA 2 with good stability and biocompatibility. ► The as-formed GS–TCDA–TBA 2 bioconjugates were captured onto the electrode surface via “sandwich” reaction, obtaining a considerably enhanced ECL signal due to the synergistic amplification of PTCDA and GS on the ECL intensity of S2O8 2−. ► To the best of our knowledge, synergistic amplification of PTCDA and GS on the ECL signal of S2O8 2− was first reported here to develop a sensitive aptasensor.An efficient strategy for unmodified nucleotide-mediated dispersion of magnetic nanoparticles, leading to a highly sensitive MRI-based mercury ion assay
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Guohai Liang, Peng Zhang, Huixiang Li, Zhengyong Zhang, Hui Chen, Song Zhang, Jilie Kong
It is highly attractive to develop a detection system that is not only sensitive and selective but also simple, rapid, practical and cost-effective in operation. Here, we report an interesting observation that single-stranded oligonucleotide (ssDNA) can adsorb efficiently on carboxylic acid-functionalized magnetic nanoparticles (CAMNPs) and stabilize the nanoparticles against aggregation in weakly acidic solution. The adsorbing rate closely correlates with the pH of the solution, the temperature and the sequence length of ssDNA. On the basis of this observation, we have designed a highly sensitive, non-sandwich type magnetic relaxation-based detection system for quantitatively probing mercury ion. The assay is independent of the sample's optical properties, requires no covalent modification of the ssDNA or the CAMNPs surfaces, and can be used for high-throughput analysis. By varying the concentration of CAMNPs, four orders of dynamic response range and a detection limit of 0.3nM for Hg2+ are achieved. Moreover, we developed a multi-sample assay to detect Hg2+ in real environmental samples with high sensitivity, selectivity and efficiency.
Source:Analytica Chimica Acta, Volume 726
Guohai Liang, Peng Zhang, Huixiang Li, Zhengyong Zhang, Hui Chen, Song Zhang, Jilie Kong
It is highly attractive to develop a detection system that is not only sensitive and selective but also simple, rapid, practical and cost-effective in operation. Here, we report an interesting observation that single-stranded oligonucleotide (ssDNA) can adsorb efficiently on carboxylic acid-functionalized magnetic nanoparticles (CAMNPs) and stabilize the nanoparticles against aggregation in weakly acidic solution. The adsorbing rate closely correlates with the pH of the solution, the temperature and the sequence length of ssDNA. On the basis of this observation, we have designed a highly sensitive, non-sandwich type magnetic relaxation-based detection system for quantitatively probing mercury ion. The assay is independent of the sample's optical properties, requires no covalent modification of the ssDNA or the CAMNPs surfaces, and can be used for high-throughput analysis. By varying the concentration of CAMNPs, four orders of dynamic response range and a detection limit of 0.3nM for Hg2+ are achieved. Moreover, we developed a multi-sample assay to detect Hg2+ in real environmental samples with high sensitivity, selectivity and efficiency.
Graphical Abstract
Graphical abstract Highlights
► Single-stranded oligonucleotide (ssDNA) can adsorb efficiently on carboxylic acid-functionalized magnetic nanoparticles (CAMNPs). ► We use ssDNA to stabilize the CAMNPs against aggregation in weakly acidic solution. ► We develop a non-sandwich type magnetic relaxation-based detection system for quantitatively probing mercury ion (Hg2+). ► We use the MRI-based high-throughput screening method to detect Hg2+ in 40 samples at the same time.Ultrasensitive detection of ovarian cancer marker using immunoliposomes and gold nanoelectrodes
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Subramanian Viswanathan, Chinnakkaruppanan Rani, Cristina Delerue-Matos
Mucin-16 (MUC16) is the established ovarian cancer marker used to follow the disease during or after treatment for epithelial ovarian cancer. The emerging science of cancer markers also demands for the new sensitive detection methods. In this work, we have developed an electrochemical immunosensor for antigen MUC16 using gold nanoelectrode ensemble (GNEE) and ferrocene carboxylic acid encapsulated liposomes tethered with monoclonal anti-Mucin-16 antibodies (αMUC16). GNEEs were fabricated by electroless deposition of the gold within the pores of polycarbonate track-etched membranes. Afterwards, αMUC16 were immobilized on preformed self-assembled monolayer of cysteamine on the GNEE via cross-linking with EDC-Sulfo-NHS. A sandwich immunoassay was performed on αMUC16 functionalized GNEE with MUC16 and immunoliposomes. The differential pulse voltammetry was employed to quantify the faradic redox response of ferrocene carboxylic acid released from immunoliposomes. The dose–response curve for MUC16 concentration was found between the range of 0.001–300UmL−1. The lowest detection limit was found to be 5×10−4 UmL−1 (S/N=3). We evaluated the performance of this developed immunosensor with commercial ELISA assay by comparing results obtained from spiked serum samples and real blood serum samples from volunteers.
Source:Analytica Chimica Acta, Volume 726
Subramanian Viswanathan, Chinnakkaruppanan Rani, Cristina Delerue-Matos
Mucin-16 (MUC16) is the established ovarian cancer marker used to follow the disease during or after treatment for epithelial ovarian cancer. The emerging science of cancer markers also demands for the new sensitive detection methods. In this work, we have developed an electrochemical immunosensor for antigen MUC16 using gold nanoelectrode ensemble (GNEE) and ferrocene carboxylic acid encapsulated liposomes tethered with monoclonal anti-Mucin-16 antibodies (αMUC16). GNEEs were fabricated by electroless deposition of the gold within the pores of polycarbonate track-etched membranes. Afterwards, αMUC16 were immobilized on preformed self-assembled monolayer of cysteamine on the GNEE via cross-linking with EDC-Sulfo-NHS. A sandwich immunoassay was performed on αMUC16 functionalized GNEE with MUC16 and immunoliposomes. The differential pulse voltammetry was employed to quantify the faradic redox response of ferrocene carboxylic acid released from immunoliposomes. The dose–response curve for MUC16 concentration was found between the range of 0.001–300UmL−1. The lowest detection limit was found to be 5×10−4 UmL−1 (S/N=3). We evaluated the performance of this developed immunosensor with commercial ELISA assay by comparing results obtained from spiked serum samples and real blood serum samples from volunteers.
Graphical Abstract
Graphical abstract Highlights
► PEGylated liposome biolabel was used for signal amplification. ► GNEE is an efficient support for antibody and electrochemical transduction. ► LOD was found 5×10−4 UmL−1 of MUC16 in blood serum. ► This MUC16 immunosensor is a better alternative to ELISA in clinical analysis.Improvement of the homogeneity of protein-imprinted polymer films by orientated immobilization of the template
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Lijian Liu, Jingjing Zheng, Guijie Fang, Weihong Xie
A method for preparing homogeneous protein-imprinted polymer films with orientated immobilization of template is described. The template methyl parathion hydrolase (MPH) was modified with a peptide linker (Gly-Ser)5–Cys and was immobilized on a cover glass with a fixed orientation via the linker. The activity of the fusion enzyme (MPH-L) was evaluated by determining the product's absorbance at 405nm (A 405). Both the free and the immobilized MPH-L showed higher retention of the bioactivity than the wide type enzyme (MPH-W) as revealed by the A 405 values for MPH-Lfree/MPH-Wfree (1.159/1.111) and for MPH-Limmobilized/MPH-Wimmobilized (0.348/0.118). The immobilized MPH-L also formed a more homogeneous template stamp compared to the immobilized MPH-W. The molecularly imprinted polymer films prepared with the immobilized MPH-L exhibited high homogeneity with low Std. Deviations of 80 and 200 from the CL intensity mean volumes which were observed for batch-prepared films and an individual film, respectively. MPH-L-imprinted polymer film also had a larger template binding capacity indicated by higher CL intensity mean volume of 3900 INT over 2500 INT for MPH-W-imprinted films. The imprinted film prepared with the orientated immobilization of template showed an imprinting factor of 1.7, while the controls did not show an imprinting effect.
Source:Analytica Chimica Acta, Volume 726
Lijian Liu, Jingjing Zheng, Guijie Fang, Weihong Xie
A method for preparing homogeneous protein-imprinted polymer films with orientated immobilization of template is described. The template methyl parathion hydrolase (MPH) was modified with a peptide linker (Gly-Ser)5–Cys and was immobilized on a cover glass with a fixed orientation via the linker. The activity of the fusion enzyme (MPH-L) was evaluated by determining the product's absorbance at 405nm (A 405). Both the free and the immobilized MPH-L showed higher retention of the bioactivity than the wide type enzyme (MPH-W) as revealed by the A 405 values for MPH-Lfree/MPH-Wfree (1.159/1.111) and for MPH-Limmobilized/MPH-Wimmobilized (0.348/0.118). The immobilized MPH-L also formed a more homogeneous template stamp compared to the immobilized MPH-W. The molecularly imprinted polymer films prepared with the immobilized MPH-L exhibited high homogeneity with low Std. Deviations of 80 and 200 from the CL intensity mean volumes which were observed for batch-prepared films and an individual film, respectively. MPH-L-imprinted polymer film also had a larger template binding capacity indicated by higher CL intensity mean volume of 3900 INT over 2500 INT for MPH-W-imprinted films. The imprinted film prepared with the orientated immobilization of template showed an imprinting factor of 1.7, while the controls did not show an imprinting effect.
Graphical Abstract
Graphical abstract Highlights
► MPH was genetically modified at its C-terminal with (Gly-Ser)5–Cys. ► MPH-L was immobilized with fixed orientation via disulfide chemistry. ► The immobilized MPH-L retained the activity of MPH. ► MPH-L formed a homogeneous template. ► Homogeneous MIP film was obtained with orientated immobilization of the template.Influence of hole mobility on the response characteristics of p-type nickel oxide thin film based glucose biosensor
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Manisha Tyagi, Monika Tomar, Vinay Gupta
RF sputtered p-type nickel oxide (NiO) thin film exhibiting tunable semiconductor character which in turns enhanced its functional properties. NiO thin film with high hole mobility is developed as a potential matrix for the realization of glucose biosensor. NiO thin film prepared under the optimized deposition conditions offer good electrical conductivity (1.5×10−3 Ω−1-cm−1) with high hole mobility (2.8cm2 V−1 s−1). The bioelectrode (GO x /NiO/ITO/glass) exhibits a low value of Michaelis–Menten constant (K m =1.05mM), indicating high affinity of the immobilized GO x toward the analyte (glucose). Due to the high surface coverage (2.32×10−7 molcm−2) of the immobilized enzyme on to the NiO matrix and its high electrocatalytic activity, the prepared biosensor exhibits a high sensitivity of 0.1mA(mM−1-cm−2) and a good linearity from 25 to 300mgdL−1 of glucose concentration with fast response time of 5s. Various functional properties of the material (mobility, crystallinity and stress) are found to influence the charge communication feature of NiO thin film matrix to a great extent, resulting in enhanced sensing response characteristics.
Source:Analytica Chimica Acta, Volume 726
Manisha Tyagi, Monika Tomar, Vinay Gupta
RF sputtered p-type nickel oxide (NiO) thin film exhibiting tunable semiconductor character which in turns enhanced its functional properties. NiO thin film with high hole mobility is developed as a potential matrix for the realization of glucose biosensor. NiO thin film prepared under the optimized deposition conditions offer good electrical conductivity (1.5×10−3 Ω−1-cm−1) with high hole mobility (2.8cm2 V−1 s−1). The bioelectrode (GO x /NiO/ITO/glass) exhibits a low value of Michaelis–Menten constant (K m =1.05mM), indicating high affinity of the immobilized GO x toward the analyte (glucose). Due to the high surface coverage (2.32×10−7 molcm−2) of the immobilized enzyme on to the NiO matrix and its high electrocatalytic activity, the prepared biosensor exhibits a high sensitivity of 0.1mA(mM−1-cm−2) and a good linearity from 25 to 300mgdL−1 of glucose concentration with fast response time of 5s. Various functional properties of the material (mobility, crystallinity and stress) are found to influence the charge communication feature of NiO thin film matrix to a great extent, resulting in enhanced sensing response characteristics.
Graphical Abstract
Graphical abstract Highlights
► Manuscript emphasizes that p-type semiconducting matrix is attractive for biosensor with enhanced response. ► Hole mobility and stress in the matrix play major role in governing the sensing response characteristics. ► p-type NiO films act as efficient matrix with high sensitivity for realization of integrated biochip.Carbon nanoparticles from corn stalk soot and its novel application as stationary phase of hydrophilic interaction chromatography and per aqueous liquid chromatography
25 April 2012,
10:43:57
Publication year:
2012
Source:Analytica Chimica Acta, Volume 726
Yuanyuan Li, Luan Xu, Tong Chen, Xiaoyan Liu, Zhigang Xu, Haixia Zhang
Carbon nanoparticles (CNPs) (6–18nm in size) were prepared by refluxing corn stalk soot in nitric acid. The obtained acid-oxidized CNPs are soluble in water due to the existence of carboxylic and hydroxyl groups. 13C NMR measurement shows the CNPs are mainly of sp2 and sp3 carbon structure different from CNPs obtained from candle soot and natural gas soot. Furthermore, these CNPs exhibit unique photoluminescence properties. Interestingly, the CNPs might be exploited to immobilize on the surface of porous silica particles as chromatographic stationary phase. The resultant packing material was evaluated by high-performance liquid chromatography, indicating that the new stationary phase could be used in hydrophilic interaction liquid chromatography (HILIC) and per aqueous liquid chromatography (PALC) modes. The separation of five nucleosides, four sulfa compounds and safflower injection was achieved by using the new column in the HILIC and PALC modes, respectively.
Source:Analytica Chimica Acta, Volume 726
Yuanyuan Li, Luan Xu, Tong Chen, Xiaoyan Liu, Zhigang Xu, Haixia Zhang
Carbon nanoparticles (CNPs) (6–18nm in size) were prepared by refluxing corn stalk soot in nitric acid. The obtained acid-oxidized CNPs are soluble in water due to the existence of carboxylic and hydroxyl groups. 13C NMR measurement shows the CNPs are mainly of sp2 and sp3 carbon structure different from CNPs obtained from candle soot and natural gas soot. Furthermore, these CNPs exhibit unique photoluminescence properties. Interestingly, the CNPs might be exploited to immobilize on the surface of porous silica particles as chromatographic stationary phase. The resultant packing material was evaluated by high-performance liquid chromatography, indicating that the new stationary phase could be used in hydrophilic interaction liquid chromatography (HILIC) and per aqueous liquid chromatography (PALC) modes. The separation of five nucleosides, four sulfa compounds and safflower injection was achieved by using the new column in the HILIC and PALC modes, respectively.
Graphical Abstract
Technicians usually thrust this borderline with the potential involving just about any mixer mill material to limitations which render it useful with the objective and also style. Seldom can some sort of material arrive pure mainly because it is typically alloyed or perhaps mixed with various other elements to make this stronger plus more resilient.
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