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Multi-element determination of Pt, Pd and Ir traces in environmental samples by ICP-MS after pre-concentration
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Manuel L.Alonso Castillo, Amparo García de Torres, Elisa Vereda Alonso, Mª Teresa Siles Cordero, José Manuel Cano Pavón
An automated flow analysis method with on-line column pre-concentration/ inductively coupled plasma mass spectrometry (ICP-MS) was developed for the simultaneous determination of Pt, Pd and Ir in environmental samples. The system is based on retention of the analytes onto a column filled with 1,5-bis (2-pyridyl)-3-sulphophenyl methylene thiocarbonohydrazide immobilized on an aminopropyl-controlled pore glass (PSTH-cpg) placed in the injection valve of a simple flow manifold. The retained platinum group metals (PGMs) were subsequently eluted with a mixture of HNO3 and thiourea. The effects of chemicals and flow variables were investigated. The optimized operating conditions were: sample pH 3.2, sample flow rate: 1.1mLmin−1; eluent flow rate: 2.1mLmin−1 and eluent 0.03% m/v thiourea solution in 3.2% (v/v) HNO3. The detection limits obtained were 78.5ngL−1 for Pt, 55.5ngL−1 for Pd and 0.1ngL−1 for Ir. The enrichment factors were 18, 2.3 and 43 for Pt, Pd and Ir, respectively. The accuracy of the method was checked by the analysis of certified reference materials and by determining the analytes content in spiked environmental samples. Recovery was found to be in the range of 93–107% in all cases.
Source:Talanta
Manuel L.Alonso Castillo, Amparo García de Torres, Elisa Vereda Alonso, Mª Teresa Siles Cordero, José Manuel Cano Pavón
An automated flow analysis method with on-line column pre-concentration/ inductively coupled plasma mass spectrometry (ICP-MS) was developed for the simultaneous determination of Pt, Pd and Ir in environmental samples. The system is based on retention of the analytes onto a column filled with 1,5-bis (2-pyridyl)-3-sulphophenyl methylene thiocarbonohydrazide immobilized on an aminopropyl-controlled pore glass (PSTH-cpg) placed in the injection valve of a simple flow manifold. The retained platinum group metals (PGMs) were subsequently eluted with a mixture of HNO3 and thiourea. The effects of chemicals and flow variables were investigated. The optimized operating conditions were: sample pH 3.2, sample flow rate: 1.1mLmin−1; eluent flow rate: 2.1mLmin−1 and eluent 0.03% m/v thiourea solution in 3.2% (v/v) HNO3. The detection limits obtained were 78.5ngL−1 for Pt, 55.5ngL−1 for Pd and 0.1ngL−1 for Ir. The enrichment factors were 18, 2.3 and 43 for Pt, Pd and Ir, respectively. The accuracy of the method was checked by the analysis of certified reference materials and by determining the analytes content in spiked environmental samples. Recovery was found to be in the range of 93–107% in all cases.
Highlights
► The determination of PGMs at ultratrace concentration level in environmental samples is achieved. ► An automatic solid phase microextraction system via FI-ICP-MS is developed. ► The proposed method is simple, sensible and fast. ► The chelating resin employed (PSTH-cpg) has numerous advantages compared with other sorbents.Bismuth film electrode at a silver solid amalgam substrate as a new tool for voltammetric determination of electrochemically reducible organic compounds
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Dana Deýlová, Vlastimil Vyskočil, Jiří Barek, Anastasios Economou
New type of bismuth film electrode prepared by electrodeposition of bismuth film on a silver solid amalgam substrate (BiF-AgSAE) was tested as a sensor for voltammetric determination of electrochemically reducible organic substances using 2-amino-6-nitrobenzothiazole (ANBT) as a model analyte. Using the optimized conditions (a 9:1 (v/v) mixture of aqueous Britton–Robinson buffer solution (pH 10.0) and methanol), the limits of quantification are 0.16µmolL−1 for direct current voltammetry (DCV) and 0.22µmolL−1 for differential pulse voltammetry (DPV). The obtained calibration dependences are linear in the concentration range from 0.2 to 100µmolL−1 and the practical applicability of the newly developed electrode for the direct determination of ANBT in tap and mineral water model samples was confirmed in this concentration range.
Source:Talanta
Dana Deýlová, Vlastimil Vyskočil, Jiří Barek, Anastasios Economou
New type of bismuth film electrode prepared by electrodeposition of bismuth film on a silver solid amalgam substrate (BiF-AgSAE) was tested as a sensor for voltammetric determination of electrochemically reducible organic substances using 2-amino-6-nitrobenzothiazole (ANBT) as a model analyte. Using the optimized conditions (a 9:1 (v/v) mixture of aqueous Britton–Robinson buffer solution (pH 10.0) and methanol), the limits of quantification are 0.16µmolL−1 for direct current voltammetry (DCV) and 0.22µmolL−1 for differential pulse voltammetry (DPV). The obtained calibration dependences are linear in the concentration range from 0.2 to 100µmolL−1 and the practical applicability of the newly developed electrode for the direct determination of ANBT in tap and mineral water model samples was confirmed in this concentration range.
Highlights
► Introduction of a novel bismuth film electrode applicable for cathodic voltammetry. ► First use of silver solid amalgam as a substrate for the bismuth film deposition. ► Sensitive voltammetric determination of genotoxic 2-amino-6-nitrobenzothiazole. ► Developed methods successfully verified on model samples of tap and mineral water. ► Limits of quantification for the determined analyte in submicromolar concentrations.An amperometric sensor for the determination of benzophenone in food packaging materials based on the electropolymerized molecularly imprinted poly-o-phenylenediamine film
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Haidong Li, Huaimin Guan, Hong Dai, Yuejin Tong, Xianen Zhao, Wenjing Qi, Saadat Majeed, Guobao Xu
Benzophenone is one of the most commonly used photoinitiators of UV-cured inks on the food packaging materials and can migrate into the foodstuffs. In this study, an amperometric benzophenone sensor based on molecularly imprinted polymer (MIP) was successfully constructed for the first time. The sensor was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode (GCE) in the presence of template benzophenone, and then removing template by immersing poly-o-phenylenediamine film-modified GCE in ethanol. The molecularly imprinted sensor was tested in the presence or absence of benzophenone by cyclic voltammetry and linear sweep voltammetry to verify the changes in the redox peak currents of potassium ferricyanide. The sensor responded sensitively to benzophenone over a linear range of 0.05 to 5μM with a detection limit of 10nM. The imprinted sensor showed high recognition ability for benzophenone and was successfully applied to the determination of benzophenone in food packaging material samples.
Source:Talanta
Haidong Li, Huaimin Guan, Hong Dai, Yuejin Tong, Xianen Zhao, Wenjing Qi, Saadat Majeed, Guobao Xu
Benzophenone is one of the most commonly used photoinitiators of UV-cured inks on the food packaging materials and can migrate into the foodstuffs. In this study, an amperometric benzophenone sensor based on molecularly imprinted polymer (MIP) was successfully constructed for the first time. The sensor was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode (GCE) in the presence of template benzophenone, and then removing template by immersing poly-o-phenylenediamine film-modified GCE in ethanol. The molecularly imprinted sensor was tested in the presence or absence of benzophenone by cyclic voltammetry and linear sweep voltammetry to verify the changes in the redox peak currents of potassium ferricyanide. The sensor responded sensitively to benzophenone over a linear range of 0.05 to 5μM with a detection limit of 10nM. The imprinted sensor showed high recognition ability for benzophenone and was successfully applied to the determination of benzophenone in food packaging material samples.
Highlights
► An amperometric benzophenone MI P sensor has been reported for the first time. ► The MIP sensor was constructed by electropolymerizing o-phenylenediamine on GCE. ► The sensor shows high sensitivity, nice selectivity and excellent stability.A highly sensitive and automated method for the determination of hypoxanthine based on lab-on-valve approach using Fe3O4/MWCNTs/β-CD modified electrode
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Yang Wang, Lu Wang, Tian Tian, Guojun Yao, Xiaoya Hu, Chun Yang, Qin Xu
A Fe3O4/multiwall carbon nanotubes/β-cyclodextrin (Fe3O4/MWCNTs/β-CD) modified electrode, for highly sensitive and automated hypoxanthine measurements, was developed in a sequential injection lab-on-valve system. The electrochemical oxidation behavior of hypoxanthine was investigated in phosphate buffer solution by cyclic voltammetry and linear sweep voltammetry. The Fe3O4/MWCNTs/β-CD modified electrode exhibits preferably analytical characteristics in electrocatalytic activity towards the oxidation of hypoxanthine. Under the optimized conditions, the log oxidation peak current intensity was proportional to log hypoxanthine concentration covering the range from 5.0×10−8 to 1.0×10−5 molL−1 with a correlation coefficient of 0.9965. A detection limit of 0.3×10–8 mol L−1 was achieved along with a sampling frequency of 20h−1. This hyphenated system offers some advantages in terms of rapidness, sensitivity and ease of manipulation. Its further applications were utilized for the determination of hypoxanthine in meat samples.
Source:Talanta
Yang Wang, Lu Wang, Tian Tian, Guojun Yao, Xiaoya Hu, Chun Yang, Qin Xu
A Fe3O4/multiwall carbon nanotubes/β-cyclodextrin (Fe3O4/MWCNTs/β-CD) modified electrode, for highly sensitive and automated hypoxanthine measurements, was developed in a sequential injection lab-on-valve system. The electrochemical oxidation behavior of hypoxanthine was investigated in phosphate buffer solution by cyclic voltammetry and linear sweep voltammetry. The Fe3O4/MWCNTs/β-CD modified electrode exhibits preferably analytical characteristics in electrocatalytic activity towards the oxidation of hypoxanthine. Under the optimized conditions, the log oxidation peak current intensity was proportional to log hypoxanthine concentration covering the range from 5.0×10−8 to 1.0×10−5 molL−1 with a correlation coefficient of 0.9965. A detection limit of 0.3×10–8 mol L−1 was achieved along with a sampling frequency of 20h−1. This hyphenated system offers some advantages in terms of rapidness, sensitivity and ease of manipulation. Its further applications were utilized for the determination of hypoxanthine in meat samples.
Highlights
► Fe3O4/MWCNTs/β-CD materials were synthesized as a modifier on the glassy carbon electrode. ► The material was used for the first time in a LOV system coupled with LSV to detect hypoxanthine. ► Results exhibited the developed method is automated and highly sensitive. ► Satisfactory results were obtained when the assay was applied in the analysis of real samples.Novel Spectroscopic Sensor for the Hydroxyl Radical Scavenging Activity Measurement of Biological Samples
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Burcu Bekdeşer, Mustafa Özyürek, Kubilay Güçlü, Reşat Apak
A novel spectroscopic sensor was developed and validated for hydroxyl radical scavenging (HRS) activity estimation using terephthalate (TP) as probe. This sensor was designed by electrostatic immobilization of the chromogenic oxidizing agent of the CUPric Reducing Antioxidant Capacity (CUPRAC) method, Cu(II)-Neocuproine (Cu(II)-Nc) complex, on a Nafion cation-exchange membrane, and the spectrophotometric assay developed in aqueous-alcoholic solutions was integrated to the CUPRAC sensor. Hydroxyl radicals (•OH) generated from an equivalent mixture of Fe(II)+EDTA with hydrogen peroxide attacked both the probe and the •OH scavengers in 37°C-incubated solutions for 1/2h. The HRS activity was measured using the decrease in CUPRAC absorbance at 450nm–arising from the reduction of Cu(II)-Nc reagent to the Cu(I)-neocuproine chelate– of the hydroxylated probe (TP) undergoing radical attack in the presence of •OH scavengers. The HRS activity was evaluated as the second-order rate constants of biologically active compounds for •OH scavenging and also as the percentage scavenging of a measured compound or sample relative to a reference compound. Using this reaction, a kinetic approach was adopted to assess the HRS activity of amino acids, plasma- and thiol-antioxidants. This assay, applicable to small molecule antioxidants and tissue homogenates, proved to be efficient for serine and albumin for which the widely used TBARS (thiobarbituric acid−reactive substances) test is nonresponsive. Under optimal conditions, about half of the probe (TP) was converted into 2-hydroxyterephthalate (hTP), and this monohydroxylated derivative, being the only product of hydroxylation, was a more specific marker of •OH than the non-specific malondialdehyde end-product of the TBARS test. The sensor gave a linear response to scavenger concentration in the competition kinetic equation.
Source:Talanta
Burcu Bekdeşer, Mustafa Özyürek, Kubilay Güçlü, Reşat Apak
A novel spectroscopic sensor was developed and validated for hydroxyl radical scavenging (HRS) activity estimation using terephthalate (TP) as probe. This sensor was designed by electrostatic immobilization of the chromogenic oxidizing agent of the CUPric Reducing Antioxidant Capacity (CUPRAC) method, Cu(II)-Neocuproine (Cu(II)-Nc) complex, on a Nafion cation-exchange membrane, and the spectrophotometric assay developed in aqueous-alcoholic solutions was integrated to the CUPRAC sensor. Hydroxyl radicals (•OH) generated from an equivalent mixture of Fe(II)+EDTA with hydrogen peroxide attacked both the probe and the •OH scavengers in 37°C-incubated solutions for 1/2h. The HRS activity was measured using the decrease in CUPRAC absorbance at 450nm–arising from the reduction of Cu(II)-Nc reagent to the Cu(I)-neocuproine chelate– of the hydroxylated probe (TP) undergoing radical attack in the presence of •OH scavengers. The HRS activity was evaluated as the second-order rate constants of biologically active compounds for •OH scavenging and also as the percentage scavenging of a measured compound or sample relative to a reference compound. Using this reaction, a kinetic approach was adopted to assess the HRS activity of amino acids, plasma- and thiol-antioxidants. This assay, applicable to small molecule antioxidants and tissue homogenates, proved to be efficient for serine and albumin for which the widely used TBARS (thiobarbituric acid−reactive substances) test is nonresponsive. Under optimal conditions, about half of the probe (TP) was converted into 2-hydroxyterephthalate (hTP), and this monohydroxylated derivative, being the only product of hydroxylation, was a more specific marker of •OH than the non-specific malondialdehyde end-product of the TBARS test. The sensor gave a linear response to scavenger concentration in the competition kinetic equation.
Highlights
► OH scavenging measurement is vital for biochemical research on oxidative stress. ► An optical sensor was designed for hydroxyl radical detection with CUPRAC method. ► Using competition kinetics, sensor response to scavenger concentration was linear. ► Colorimetric sensor was statistically validated against HPLC and TBARS methods.Graphene-Carbon Paste Electrode for Cadmium and Lead Ion Monitoring in a Flow-based System
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Wanida Wonsawat, Suchada Chuanuwatanakul, Wijitar Dungchai, Eakkasit Punrat, Shoji Motomizu, Orawon Chailapakul
An environmentally friendly electrode for determining Cd2+ and Pb2+ levels in an automated flow system was successfully developed. Cyclic voltammetry and square wave anodic stripping voltammetry (SWASV) coupled with sequential injection analysis (SIA) were employed to study the electrochemical behavior of the electrode. The in situ bismuth-modified graphene carbon paste electrode (Bi-GCPE) exhibited excellent electrooxidation of Cd2+ and Pb2+ in the automated flow system with a significantly higher peak current for both metal ions compared with the unmodified CPE. The limits of detection from this method were 0.07 and 0.04μgL−1 for Cd2+ and Pb2+, respectively, with a linear oxidation peak current response for Cd2+ and Pb2+ in the range of 0.10 to 50.0μgL−1 under optimum conditions. The Bi-GCPE was also applied for the determination of Cd2+ and Pb2+ in low- (tap water) and high- (sea bass fish and undulated surf clam tissues) matrix complexity samples by automated flow system. The recoveries were acceptable and ranged from 70.4 to 120% for Cd2+ and 65.8 to 113.5% for Pb2+.
Source:Talanta
Wanida Wonsawat, Suchada Chuanuwatanakul, Wijitar Dungchai, Eakkasit Punrat, Shoji Motomizu, Orawon Chailapakul
An environmentally friendly electrode for determining Cd2+ and Pb2+ levels in an automated flow system was successfully developed. Cyclic voltammetry and square wave anodic stripping voltammetry (SWASV) coupled with sequential injection analysis (SIA) were employed to study the electrochemical behavior of the electrode. The in situ bismuth-modified graphene carbon paste electrode (Bi-GCPE) exhibited excellent electrooxidation of Cd2+ and Pb2+ in the automated flow system with a significantly higher peak current for both metal ions compared with the unmodified CPE. The limits of detection from this method were 0.07 and 0.04μgL−1 for Cd2+ and Pb2+, respectively, with a linear oxidation peak current response for Cd2+ and Pb2+ in the range of 0.10 to 50.0μgL−1 under optimum conditions. The Bi-GCPE was also applied for the determination of Cd2+ and Pb2+ in low- (tap water) and high- (sea bass fish and undulated surf clam tissues) matrix complexity samples by automated flow system. The recoveries were acceptable and ranged from 70.4 to 120% for Cd2+ and 65.8 to 113.5% for Pb2+.
Highlights
► Graphene modified CPE was used to develop novel method in flow-based system. ► Automated flow-based system is employed for the determination of heavy metal ions. ► This method was successfully applied for the complicated samples.Dispersive liquid-liquid microextraction with non-halogenated extractants for trihalomethanes determination in tap and swimming pool water
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
T. Rodríguez-Cabo, M. Ramil, I. Rodríguez, R. Cela
An effective, low solvent consumption, reduced cost and high throughput sample preparation method for the determination of four trihalomethanes (THMs) in tap and swimming pool water samples is presented. THMs extraction and concentration were performed by dispersive liquid-liquid microextraction (DLLME), based on the use of non-halogenated and low volatile solvents as extractants. Analytes were further determined by gas chromatography with micro-electron capture detection (GC-microECD). Under optimized conditions, the proposed method uses 18mL volume samples, 0.7mL of acetone (dispersant) and 0.05mL of 1-undecanol (extractant). Achieved enrichment factors (EFs) varied from 67 to 104 times, the limits of quantification (LOQs) stayed between 0.05 and 1.3ngmL−1, and an excellent linearity was noticed up to 100ngmL−1. Relative recoveries, measured for spiked aliquots of tap and swimming pool water samples, remained between 79% and 113%, with associated standard deviations below 12%. The applicability of the developed methodology was demonstrated with chlorinated water samples analysis. As regards tap water samples, the sum of THMs concentrations remained under the limit fixed by the European Union (100ngmL−1); however, some samples contained levels close to 80ngmL−1, the maximum allowable concentration established by the United States Environmental Protection Agency (EPA).
Source:Talanta
T. Rodríguez-Cabo, M. Ramil, I. Rodríguez, R. Cela
An effective, low solvent consumption, reduced cost and high throughput sample preparation method for the determination of four trihalomethanes (THMs) in tap and swimming pool water samples is presented. THMs extraction and concentration were performed by dispersive liquid-liquid microextraction (DLLME), based on the use of non-halogenated and low volatile solvents as extractants. Analytes were further determined by gas chromatography with micro-electron capture detection (GC-microECD). Under optimized conditions, the proposed method uses 18mL volume samples, 0.7mL of acetone (dispersant) and 0.05mL of 1-undecanol (extractant). Achieved enrichment factors (EFs) varied from 67 to 104 times, the limits of quantification (LOQs) stayed between 0.05 and 1.3ngmL−1, and an excellent linearity was noticed up to 100ngmL−1. Relative recoveries, measured for spiked aliquots of tap and swimming pool water samples, remained between 79% and 113%, with associated standard deviations below 12%. The applicability of the developed methodology was demonstrated with chlorinated water samples analysis. As regards tap water samples, the sum of THMs concentrations remained under the limit fixed by the European Union (100ngmL−1); however, some samples contained levels close to 80ngmL−1, the maximum allowable concentration established by the United States Environmental Protection Agency (EPA).
Highlights
► Dispersive liquid microextraction with non-halogenated, low-volatile solvents. ► High-throughput and low cost trihalomethanes extraction. ► Optimization, validation and application to tap and swimming-pool waters.Synthesis of water-compatible imprinted polymers of in situ produced fructosazine and 2,5-deoxyfructosazine
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Nathaly Henry, Raphaël Delépée, Jean-Marc Seigneuret, Luigi A. Agrofoglio
Fructosazine and 2,5-deoxyfructosazine are two natural chemicals with various applications as flavoring agents in food and tobacco industry; the 2,5-deoxyfructosazine has also anti-diabetic and anti-inflammatory activities. In order to quantify these compounds in natural samples such as plant or food, we have developed a selective technique based on a water-compatible molecularly imprinted polymer (MIP). MIPs are prepared with a covalent approach from 2,5-deoxyfructosazine as template formed in situ by the self condensation of glucosamine with vinylphenyl boronic acid, taken as catalyst and covalent monomer during the pre-complexation step. Acrylamide and polyethylene glycol diacrylate are used as supplementary non covalent functional monomer and cross-linker, respectively. For the first time, a highly cross-linked but highly polar imprinted polymer of fructosazine and deoxyfructosazine is obtained as a solid material and not a gel. Amount of monomers is optimized to obtain high selectivity for both molecules. Results show that the MIPs prepared have a significant imprinting effect with a resulting imprinting factor of 3 for both templates. Molecularly imprinted solid-phase extraction is then performed and could be used in routine analysis to extract 2,5-deoxyfructosazine and fructosazine from soy sauce.
Source:Talanta
Nathaly Henry, Raphaël Delépée, Jean-Marc Seigneuret, Luigi A. Agrofoglio
Fructosazine and 2,5-deoxyfructosazine are two natural chemicals with various applications as flavoring agents in food and tobacco industry; the 2,5-deoxyfructosazine has also anti-diabetic and anti-inflammatory activities. In order to quantify these compounds in natural samples such as plant or food, we have developed a selective technique based on a water-compatible molecularly imprinted polymer (MIP). MIPs are prepared with a covalent approach from 2,5-deoxyfructosazine as template formed in situ by the self condensation of glucosamine with vinylphenyl boronic acid, taken as catalyst and covalent monomer during the pre-complexation step. Acrylamide and polyethylene glycol diacrylate are used as supplementary non covalent functional monomer and cross-linker, respectively. For the first time, a highly cross-linked but highly polar imprinted polymer of fructosazine and deoxyfructosazine is obtained as a solid material and not a gel. Amount of monomers is optimized to obtain high selectivity for both molecules. Results show that the MIPs prepared have a significant imprinting effect with a resulting imprinting factor of 3 for both templates. Molecularly imprinted solid-phase extraction is then performed and could be used in routine analysis to extract 2,5-deoxyfructosazine and fructosazine from soy sauce.
Highlights
► A water-compatible imprinted polymer for fructosazine and 2,5-deoxyfructosazine is formed. ► The highly polar and highly cross-linked polymer is a solid material and not a gel. ► Eco-friendly parameters were used for the design of imprinted polymers. ► The template is formed in situ by the self condensation of glucosamine. ► The vinylphenyl boronic acid is taken as catalyst and covalent monomer.A flow system with zone merging and zone trapping in the main reactor applied to spectrophotometric catalytic determination of cobalt in grasses
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Taciana F. Gomes, Ana C.F. Vida, Milton K. Sasaki, Claudineia R. Silva, Valdemir A.F. Barros, Elias A.G. Zagatto
A flow system with zone merging and zone trapping in the main reactor was proposed. The sample and reagent inserted aliquots merge together and the resulting zone is directed towards a displaceable reactor inside which its most concentrated portion is trapped. After the pre-set TRAP period, the handled sample is released towards detection. A comparison with an analogous flow system exploiting zone stopping revealed the superior characteristics of sampling rate and system operation; moreover, the sample inserted volume plays little influence on sampling rate. The system was applied to the spectrophotometric determination of cobalt in pastures, and enhanced figures of merit (sampling rate=18h−1; peak height r.s.d.=0.7%, detection limit=0.046µgL−1 Co; reagent consumption=330µg of Tiron per measurement; 98%<recovery<114%) were estimated.
Source:Talanta
Taciana F. Gomes, Ana C.F. Vida, Milton K. Sasaki, Claudineia R. Silva, Valdemir A.F. Barros, Elias A.G. Zagatto
A flow system with zone merging and zone trapping in the main reactor was proposed. The sample and reagent inserted aliquots merge together and the resulting zone is directed towards a displaceable reactor inside which its most concentrated portion is trapped. After the pre-set TRAP period, the handled sample is released towards detection. A comparison with an analogous flow system exploiting zone stopping revealed the superior characteristics of sampling rate and system operation; moreover, the sample inserted volume plays little influence on sampling rate. The system was applied to the spectrophotometric determination of cobalt in pastures, and enhanced figures of merit (sampling rate=18h−1; peak height r.s.d.=0.7%, detection limit=0.046µgL−1 Co; reagent consumption=330µg of Tiron per measurement; 98%<recovery<114%) were estimated.
Highlights
► Zone trapping is effective for zone halting inside the main reactor. ► A comparison between zone trapping and zone stopping is performed. ► The catalytic spectrophotometric determination of Co in plants is improved.Evaluation of matrix effect in determination of some bioflavonoids in food samples by LC-MS/MS method
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Andrija Ćirić, Helena Prosen, Milena Jelikić-Stankov, Predrag Đurđević
In the present work the LC-MS/MS method with solid phase extraction for simultaneous determination of bioflavonoids rutin, quercetin, hesperidin, hesperetin and kaempferol in some food samples (red onion, orange peel and honey) was developed and the matrix effect accompanying this determination was quantified. The matrix effect evaluated using postextraction addition method was found to be negative in the range −44 to −0.5%, indicating ionization suppression and strongly depended on bioflavonoid concentration. The observed matrix effect was explained taking into account the co-elution of phenolic acids, in terms of their acid-base and hydrophilic properties. The efficacy of extraction expressed as the absolute recoveries of flavonoids were 88–96%, indicating very good efficiency of extraction. The extracts of food samples obtained either by Soxhlet or ultrasonic extraction were analyzed for bioflavonoid content by LC-MS/MS method in selected reaction monitoring mode using triple quadrupole detector and standard addition method, which was found to be the most suitable calibration approach for these samples. The optimized separation was achieved on Phenomenex Gemini C18 column with gradient elution and mobile phase composition A: 2% acetic acid in water and B: acetonitrile. R s values were in the range from 1.3 to 3.1, indicating good selectivity of the method. The obtained results (mg/100g fresh weight) for different bioflavonids were for rutin 0.16, for quercetin in the range 0.65–56, for hesperidin 0.016–24, for hesperetin 0.0068–36.4 and for kaempferol 0.14–1.63 and generally show good agreement with published data. Low detection limits (0.014–0.063μg/mL) were obtained with acceptable recoveries (86–114%). Total time of analysis was less than 40min, therefore the proposed method represents significant improvement over existing methods.
Source:Talanta
Andrija Ćirić, Helena Prosen, Milena Jelikić-Stankov, Predrag Đurđević
In the present work the LC-MS/MS method with solid phase extraction for simultaneous determination of bioflavonoids rutin, quercetin, hesperidin, hesperetin and kaempferol in some food samples (red onion, orange peel and honey) was developed and the matrix effect accompanying this determination was quantified. The matrix effect evaluated using postextraction addition method was found to be negative in the range −44 to −0.5%, indicating ionization suppression and strongly depended on bioflavonoid concentration. The observed matrix effect was explained taking into account the co-elution of phenolic acids, in terms of their acid-base and hydrophilic properties. The efficacy of extraction expressed as the absolute recoveries of flavonoids were 88–96%, indicating very good efficiency of extraction. The extracts of food samples obtained either by Soxhlet or ultrasonic extraction were analyzed for bioflavonoid content by LC-MS/MS method in selected reaction monitoring mode using triple quadrupole detector and standard addition method, which was found to be the most suitable calibration approach for these samples. The optimized separation was achieved on Phenomenex Gemini C18 column with gradient elution and mobile phase composition A: 2% acetic acid in water and B: acetonitrile. R s values were in the range from 1.3 to 3.1, indicating good selectivity of the method. The obtained results (mg/100g fresh weight) for different bioflavonids were for rutin 0.16, for quercetin in the range 0.65–56, for hesperidin 0.016–24, for hesperetin 0.0068–36.4 and for kaempferol 0.14–1.63 and generally show good agreement with published data. Low detection limits (0.014–0.063μg/mL) were obtained with acceptable recoveries (86–114%). Total time of analysis was less than 40min, therefore the proposed method represents significant improvement over existing methods.
Highlights
► HPLC-MS/MS method for determination of flavonoids in food was developed and optimized. ► Matrix effect was evaluated for each food sample and corrected during method development. ► Extraction procedure was optimized achieving 88–96% of Soxhlet yield. ► Negative matrix effect (−44 to −0.5%) was confirmed and flavonoids were quantified by standard addition method.Electrochemical DNA sensors based on electropolymerized materials
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Herman C. Budnikov, Gennady A. Evtugyn, Anna V. Porfireva
The use of electropolymerized materials in the DNA sensors is reviewed with particular emphasis on their functions and specific interactions with DNA and oligonucleotides. Polyaniline, pollypyrrole, polythiophenes and polymeric forms of phenazines play significant role in the immobilization and signal transduction of DNA sensors for the detection of hybridization events, DNA-protein and other specific interactions on the sensor surface. The mechanism of electropolymerization and the influence of oligonucleotides are also considered for various types of polymers. The DNA sensor performance is classified in accordance with the biological targets and composition of the surface layer.
Source:Talanta
Herman C. Budnikov, Gennady A. Evtugyn, Anna V. Porfireva
The use of electropolymerized materials in the DNA sensors is reviewed with particular emphasis on their functions and specific interactions with DNA and oligonucleotides. Polyaniline, pollypyrrole, polythiophenes and polymeric forms of phenazines play significant role in the immobilization and signal transduction of DNA sensors for the detection of hybridization events, DNA-protein and other specific interactions on the sensor surface. The mechanism of electropolymerization and the influence of oligonucleotides are also considered for various types of polymers. The DNA sensor performance is classified in accordance with the biological targets and composition of the surface layer.
Determination of gold in geological materials by carbon slurry sampling graphite furnace atomic absorption spectrometry
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Ryszard Dobrowolski, Michał Kuryło, Magdalena Otto, Agnieszka Mróz
A simple and cost effective preconcentration method on modified activated carbons is described for the determination of traces of gold (Au) in geological samples by carbon slurry sampling graphite furnace atomic absorption spectrometry (GFAAS). The basic parameters affecting the adsorption capacity of Au(III) ions on modified activated carbons were studied in detail and the effect of activated carbons modification has been determined by studying the initial runs of adsorption isotherms. The influence of chlorides and nitrates on adsorption ability of Au(III) ions onto the modified activated carbons for diluted aqueous solution was also studied in detail in respect to the determination of gold in solid materials after digestion steps in the analytical procedure, which usually involves the application of aqua regia. SEM-EDX and XPS studies confirmed that the surface reduction of Au(III) ions to Au(0) is the main gold adsorption mechanism on the activated carbon. Determination of gold after its preconcentration on the modified activated carbon was validated by applying certified reference materials. The experimental results are in good agreement with the certified values. The proposed method has been successfully applied for the determination of Au in real samples using aqueous standards.
Source:Talanta
Ryszard Dobrowolski, Michał Kuryło, Magdalena Otto, Agnieszka Mróz
A simple and cost effective preconcentration method on modified activated carbons is described for the determination of traces of gold (Au) in geological samples by carbon slurry sampling graphite furnace atomic absorption spectrometry (GFAAS). The basic parameters affecting the adsorption capacity of Au(III) ions on modified activated carbons were studied in detail and the effect of activated carbons modification has been determined by studying the initial runs of adsorption isotherms. The influence of chlorides and nitrates on adsorption ability of Au(III) ions onto the modified activated carbons for diluted aqueous solution was also studied in detail in respect to the determination of gold in solid materials after digestion steps in the analytical procedure, which usually involves the application of aqua regia. SEM-EDX and XPS studies confirmed that the surface reduction of Au(III) ions to Au(0) is the main gold adsorption mechanism on the activated carbon. Determination of gold after its preconcentration on the modified activated carbon was validated by applying certified reference materials. The experimental results are in good agreement with the certified values. The proposed method has been successfully applied for the determination of Au in real samples using aqueous standards.
Highlights
► Slurry sampling GFAAS for Au determination in geological samples is proposed. ► The discharging activated carbon was used in the sorption process of Au(III). ► Great adsorption capacity and selectivity for Au(III) ions were confirmed. ► Low LOD and satisfactory enrichment factors were obtained for geological materials. ► XPS data proved the surface reduction as the main gold adsorption mechanism.Advances of CE-ICP-MS in speciation analysis related to metalloproteomics of anticancer drugs
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Andrei R. Timerbaev, Katarzyna Pawlak, Svetlana S. Aleksenko, Lidia S. Foteeva, Magdalena Matczuk, Maciej Jarosz
The mode of action of metal-based anticancer drugs, including their accumulation in blood, transport, delivery to cancer cell, and cell processing (together with release of an active form and possibly targeting) is largely dependent on protein binding. Among analytical methods capable of providing a better understanding of metallodrug–protein interactions, capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) detection is arguably a premier technique. Since its advent to the area of metallodrug proteomics in 2004 [1], the benefits of CE-ICP-MS became evident, stimulating further research and methodological developments. This hyphenated technique's merits comprise an ability to separate rapidly and efficiently the parent drug and protein-bound drug form(s), with no alteration of original speciation in the sample, to identify the metal-containing species due to specific ICP-MS response, to measure the binding parameters (e.g. rate and equilibrium constants), and finally to quantify the metal–protein adducts in real-world samples. This review is aimed on offering the reader a summary of applications of CE-ICP-MS to various metallodrug–protein systems, with a focus on experimental strategies in use for the assessment of binding reactivity and affinity, monitoring in vitro cellular transformations and serum binding profiles, and ex vivo metallodrug–proteomic analysis.
Source:Talanta
Andrei R. Timerbaev, Katarzyna Pawlak, Svetlana S. Aleksenko, Lidia S. Foteeva, Magdalena Matczuk, Maciej Jarosz
The mode of action of metal-based anticancer drugs, including their accumulation in blood, transport, delivery to cancer cell, and cell processing (together with release of an active form and possibly targeting) is largely dependent on protein binding. Among analytical methods capable of providing a better understanding of metallodrug–protein interactions, capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) detection is arguably a premier technique. Since its advent to the area of metallodrug proteomics in 2004 [1], the benefits of CE-ICP-MS became evident, stimulating further research and methodological developments. This hyphenated technique's merits comprise an ability to separate rapidly and efficiently the parent drug and protein-bound drug form(s), with no alteration of original speciation in the sample, to identify the metal-containing species due to specific ICP-MS response, to measure the binding parameters (e.g. rate and equilibrium constants), and finally to quantify the metal–protein adducts in real-world samples. This review is aimed on offering the reader a summary of applications of CE-ICP-MS to various metallodrug–protein systems, with a focus on experimental strategies in use for the assessment of binding reactivity and affinity, monitoring in vitro cellular transformations and serum binding profiles, and ex vivo metallodrug–proteomic analysis.
Analysis of mycotoxins in barley using ultra high liquid chromatography high resolution mass spectrometry: Comparison of efficiency and efficacy of different extraction procedures
23 July 2012,
00:36:27
Publication year:
2012
Source:Talanta
Josep Rubert, Zbynek Dzuman, Marta Vaclavikova, Milena Zachariasova, Carla Soler, Jana Hajslova
The effectiveness of four extraction methods (modified QuEChERS, matrix solid-phase dispersion (MSPD), solid-liquid extraction (SLE) and solid-phase extraction (SPE) clean-up) were evaluated for simultaneous determination of 32 mycotoxins produced by the genus Fusarium, Claviceps, Aspergillus, Penicillium and Alternaria in barley by ultra high pressure liquid chromatography coupled to ultra-high resolution mass spectrometry (UHPLC-Orbitrap® MS). The efficiency and efficacy of extraction methods were evaluated and compared in number of extracted mycotoxins and obtained recoveries. From the one point of view, QuEChERS procedure was fast and easy, as well as it was able to successfully extract all selected mycotoxins. On the other hand, SLE method, MSPD and SPE clean-up method did not extract adequately all selected mycotoxins and recoveries were not suitable enough. Thereby, method employing QuEChERS extraction connected with UHPLC-Orbitrap® MS was developed to quantify 32 mycotoxins in barley within this study. Analytical method was validated and recoveries ranged from 72 to 101% for selected mycotoxins with only one exception nivalenol (NIV) and deoxynivalenol-3-glucoside (D3G), which were lower than 67%. Relative standard deviations (RSD) were lower than 17.4% for all target mycotoxins. The lowest calibration levels (LCLs) ranged from 1 to 100µg/kg. Validated method was finally used for monitoring mycotoxins in a total of 15 Czech barley samples, when only Fusarium toxins representatives were detected in 53% of samples and the mycotoxins with the highest incidence were enniatins.
Source:Talanta
Josep Rubert, Zbynek Dzuman, Marta Vaclavikova, Milena Zachariasova, Carla Soler, Jana Hajslova
The effectiveness of four extraction methods (modified QuEChERS, matrix solid-phase dispersion (MSPD), solid-liquid extraction (SLE) and solid-phase extraction (SPE) clean-up) were evaluated for simultaneous determination of 32 mycotoxins produced by the genus Fusarium, Claviceps, Aspergillus, Penicillium and Alternaria in barley by ultra high pressure liquid chromatography coupled to ultra-high resolution mass spectrometry (UHPLC-Orbitrap® MS). The efficiency and efficacy of extraction methods were evaluated and compared in number of extracted mycotoxins and obtained recoveries. From the one point of view, QuEChERS procedure was fast and easy, as well as it was able to successfully extract all selected mycotoxins. On the other hand, SLE method, MSPD and SPE clean-up method did not extract adequately all selected mycotoxins and recoveries were not suitable enough. Thereby, method employing QuEChERS extraction connected with UHPLC-Orbitrap® MS was developed to quantify 32 mycotoxins in barley within this study. Analytical method was validated and recoveries ranged from 72 to 101% for selected mycotoxins with only one exception nivalenol (NIV) and deoxynivalenol-3-glucoside (D3G), which were lower than 67%. Relative standard deviations (RSD) were lower than 17.4% for all target mycotoxins. The lowest calibration levels (LCLs) ranged from 1 to 100µg/kg. Validated method was finally used for monitoring mycotoxins in a total of 15 Czech barley samples, when only Fusarium toxins representatives were detected in 53% of samples and the mycotoxins with the highest incidence were enniatins.
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