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Analytica Chimica Acta (v.576, #2)
Per- O-methylation reaction for structural analysis of carbohydrates by mass spectrometry by Ionel Ciucanu (pp. 147-155).
Per- O-methylation of carbohydrates is an important sample preparation step in structural analysis of complex carbohydrates, which has generated considerable interest as shown by thousands of citations in the last 10 years. This article provides a critical overview of the per- O-methylation methods applied for structural analysis of carbohydrates by mass spectrometry. The understanding of the O-methylation mechanism can help the researchers to apply the adequate O-methylation method and can generate new ideas in the effort of improving this reaction. The per- O-methylation of carbohydrates is relied upon stepwise reactions. The parameters that affect the reaction are discussed for the most important methods and are critically commented for each reaction step. The limits of each method are emphasized. The improvements of the per- O-methylation reaction are described in detail with their advantages and disadvantages and some illustrative examples are given. The methods that give complete O-methylation in non-hazardous conditions with high yields within minutes at room temperature with a very low amount of side-products are especially highlighted.
Keywords: Per-; O; -methylation; Structural analysis of carbohydrates; Mass spectrometry
Per- O-methylation reaction for structural analysis of carbohydrates by mass spectrometry by Ionel Ciucanu (pp. 147-155).
Per- O-methylation of carbohydrates is an important sample preparation step in structural analysis of complex carbohydrates, which has generated considerable interest as shown by thousands of citations in the last 10 years. This article provides a critical overview of the per- O-methylation methods applied for structural analysis of carbohydrates by mass spectrometry. The understanding of the O-methylation mechanism can help the researchers to apply the adequate O-methylation method and can generate new ideas in the effort of improving this reaction. The per- O-methylation of carbohydrates is relied upon stepwise reactions. The parameters that affect the reaction are discussed for the most important methods and are critically commented for each reaction step. The limits of each method are emphasized. The improvements of the per- O-methylation reaction are described in detail with their advantages and disadvantages and some illustrative examples are given. The methods that give complete O-methylation in non-hazardous conditions with high yields within minutes at room temperature with a very low amount of side-products are especially highlighted.
Keywords: Per-; O; -methylation; Structural analysis of carbohydrates; Mass spectrometry
Determination of benzene in gasoline using direct injection-mass spectrometry by José Luis Pérez Pavón; Miguel del Nogal Sánchez; M Esther Fernández Laespada; Carmelo García Pinto; Bernardo Moreno Cordero (pp. 156-162).
A high-speed determination of benzene in gasoline samples using a non-separative method based on direct injection into the mass spectrometer is proposed. The results obtained are very similar to those provided with fast GC–MS.The calibration set was made up of gasoline samples in which the benzene was determined chromatographically and samples of gasoline subjected to a process of evaporation – until the complete disappearance of the original benzene – to which known concentrations of this compound had been added. A PLS1 multivariate calibration model was constructed. Cross-validation was used to select the optimum number of PLS components. The prediction capacity of the model was checked with an additional group of gasoline samples that had not been used either in the construction or in the validation of the model.With the direct injection method proposed here it was possible to analyse 24 samples over a period of 1h. The direct injection method is rapid, simple and – in view of the results – highly suitable for the determination of benzene in gasoline samples.
Keywords: Benzene; Gasoline; Direct injection; Mass spectrometry
Determination of benzene in gasoline using direct injection-mass spectrometry by José Luis Pérez Pavón; Miguel del Nogal Sánchez; M Esther Fernández Laespada; Carmelo García Pinto; Bernardo Moreno Cordero (pp. 156-162).
A high-speed determination of benzene in gasoline samples using a non-separative method based on direct injection into the mass spectrometer is proposed. The results obtained are very similar to those provided with fast GC–MS.The calibration set was made up of gasoline samples in which the benzene was determined chromatographically and samples of gasoline subjected to a process of evaporation – until the complete disappearance of the original benzene – to which known concentrations of this compound had been added. A PLS1 multivariate calibration model was constructed. Cross-validation was used to select the optimum number of PLS components. The prediction capacity of the model was checked with an additional group of gasoline samples that had not been used either in the construction or in the validation of the model.With the direct injection method proposed here it was possible to analyse 24 samples over a period of 1h. The direct injection method is rapid, simple and – in view of the results – highly suitable for the determination of benzene in gasoline samples.
Keywords: Benzene; Gasoline; Direct injection; Mass spectrometry
Determination of 36 elements in plant reference materials with different Si contents by inductively coupled plasma mass spectrometry: Comparison of microwave digestions assisted by three types of digestion mixtures by Julie Sucharová; Ivan Suchara (pp. 163-176).
Closed-vessel microwave digestion of nine standard reference plant materials (NIST, BCR, IAEA) and a laboratory standard of plant material with different Si contents assisted by HNO3+H2O2 (procedure A), HNO3+H2O2+HF+H3BO3 (procedure B) and HNO3+H2O2+HBF4 (procedure C) were used to determine the recovery of 36 elements by ICP-MS: Ag, Al, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, In, La, Li, Mn, Mo, Nd, Ni, Pb, Pr, Rb, Sb, Se, Sn, Sr, Th, Tl, U, V, W, Y, Zn. Additions of HF+H3BO3 and HBF4 in procedures B and C exceeded by 10% (B1, C1) and 100% (B2, C2) the equivalent concentrations of Si in the samples determined by ICP-OES. Most recoveries of certified elements (e.g., Al*, Cu, Mo*, Rb*, Sb*, Th) decreased significantly (* p≤0.05) with increasing Si content in plant reference materials digested by procedure A, while the recoveries from procedures B and C decreased insignificantly only for Mo and Sb. Digestions B and C gave significantly higher recoveries of Al, Sb, W and REEs, which were tighter to the reference values of these elements. A similar effect was found for Cu, Fe, Li, Ni, Sn, Th, Tl, V, Zn, Ba, Rb and Sr recoveries in samples with Si contents exceeding 2000μgg−1. If the Si content in plant samples is less than 10mgg−1, digestion of 0.5g of plant samples through 0.05mL of HF and 0.5mL of 4% H3BO3 or 0.1mL of HBF4 is recommended to get satisfactory results for most of the elements. For materials with Si content exceeding 10mgg−1 the weight of the sample for digestion should be reduced to 0.25g. However, the operation of potential interferences should be taken into account and eliminated through correction equations and adequate dilution of the samples.
Keywords: Reference plant materials; Silicon content; Microwave digestion procedures; Multi-element determinations; Inductively coupled plasma mass spectrometry; Interferences; Recoveries
Determination of 36 elements in plant reference materials with different Si contents by inductively coupled plasma mass spectrometry: Comparison of microwave digestions assisted by three types of digestion mixtures by Julie Sucharová; Ivan Suchara (pp. 163-176).
Closed-vessel microwave digestion of nine standard reference plant materials (NIST, BCR, IAEA) and a laboratory standard of plant material with different Si contents assisted by HNO3+H2O2 (procedure A), HNO3+H2O2+HF+H3BO3 (procedure B) and HNO3+H2O2+HBF4 (procedure C) were used to determine the recovery of 36 elements by ICP-MS: Ag, Al, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, In, La, Li, Mn, Mo, Nd, Ni, Pb, Pr, Rb, Sb, Se, Sn, Sr, Th, Tl, U, V, W, Y, Zn. Additions of HF+H3BO3 and HBF4 in procedures B and C exceeded by 10% (B1, C1) and 100% (B2, C2) the equivalent concentrations of Si in the samples determined by ICP-OES. Most recoveries of certified elements (e.g., Al*, Cu, Mo*, Rb*, Sb*, Th) decreased significantly (* p≤0.05) with increasing Si content in plant reference materials digested by procedure A, while the recoveries from procedures B and C decreased insignificantly only for Mo and Sb. Digestions B and C gave significantly higher recoveries of Al, Sb, W and REEs, which were tighter to the reference values of these elements. A similar effect was found for Cu, Fe, Li, Ni, Sn, Th, Tl, V, Zn, Ba, Rb and Sr recoveries in samples with Si contents exceeding 2000μgg−1. If the Si content in plant samples is less than 10mgg−1, digestion of 0.5g of plant samples through 0.05mL of HF and 0.5mL of 4% H3BO3 or 0.1mL of HBF4 is recommended to get satisfactory results for most of the elements. For materials with Si content exceeding 10mgg−1 the weight of the sample for digestion should be reduced to 0.25g. However, the operation of potential interferences should be taken into account and eliminated through correction equations and adequate dilution of the samples.
Keywords: Reference plant materials; Silicon content; Microwave digestion procedures; Multi-element determinations; Inductively coupled plasma mass spectrometry; Interferences; Recoveries
A novel route for immobilization of oligonucleotides onto modified silica nanoparticles by Kota Sreenivasa Rao; Sikhakolli Usha Rani; Devarayapalli Kamakshaiah Charyulu; Kamisetty Nagendra Kumar; Bong-Kuk Lee; Hea-Yeon Lee; Tomoji Kawai (pp. 177-183).
A novel approach for immobilization of probe oligonucleotides that uses zirconium phosphate modified silica nanoparticles is proposed. The surface modification of nanoparticles was carried out in two stages. Initially binding of Zr4+ to the surface of silica nanoparticles and later treated with phosphoric acid for terminal phosphate groups. Oligonucleotide probes modified with amine group at 5′-end were strongly binds to the phosphate terminated silica nanoparticles with imidazole in presence of 0.1molL−1 EDC [ N-ethyl- N′-(3-dimethylaminopropyl) carbodiimide], as phosphate groups are more reactive towards amine group. Various studies, i.e., synthesis of silica nanoparticles, their surface modification, probe immobilization, measurement of hybridization and effect of bovine serum albumin (BSA) were carried out during optimization of reaction conditions. The significant reduction in the background signal was observed by treating the probe modified silica nanoparticles with bovine serum albumin prior to hybridization. The probe modified silica nanoparticles were retained their properties and the hybridization was induced by exposure of single-stranded DNA (ssDNA) containing silica nanoparticles to the complementary DNA in solution. The decrease in the fluorescence signal for one mismatch and three mismatch was observed upon hybridization of probe with target DNAs, while there was no response for the random target ssDNA under the same experimental conditions. The intensity of fluorescence signal was linear to the concentration of target DNA ranging from 3.9×10−9 to 3.0×10−6molL−1. A detection limit of 1.22×10−9molL−1 of oligonucleotides can be estimated. The proposed hybridization assay is simple and possesses good analytical characteristics and it can provide an effective and efficient route in the development of DNA biosensors and biochips.
Keywords: Silica nanoparticles; Tetraethyl orthosilicate (TEOS); Immobilization; Single-stranded deoxyribonucleic acid (ssDNA); Hybridization
A novel route for immobilization of oligonucleotides onto modified silica nanoparticles by Kota Sreenivasa Rao; Sikhakolli Usha Rani; Devarayapalli Kamakshaiah Charyulu; Kamisetty Nagendra Kumar; Bong-Kuk Lee; Hea-Yeon Lee; Tomoji Kawai (pp. 177-183).
A novel approach for immobilization of probe oligonucleotides that uses zirconium phosphate modified silica nanoparticles is proposed. The surface modification of nanoparticles was carried out in two stages. Initially binding of Zr4+ to the surface of silica nanoparticles and later treated with phosphoric acid for terminal phosphate groups. Oligonucleotide probes modified with amine group at 5′-end were strongly binds to the phosphate terminated silica nanoparticles with imidazole in presence of 0.1molL−1 EDC [ N-ethyl- N′-(3-dimethylaminopropyl) carbodiimide], as phosphate groups are more reactive towards amine group. Various studies, i.e., synthesis of silica nanoparticles, their surface modification, probe immobilization, measurement of hybridization and effect of bovine serum albumin (BSA) were carried out during optimization of reaction conditions. The significant reduction in the background signal was observed by treating the probe modified silica nanoparticles with bovine serum albumin prior to hybridization. The probe modified silica nanoparticles were retained their properties and the hybridization was induced by exposure of single-stranded DNA (ssDNA) containing silica nanoparticles to the complementary DNA in solution. The decrease in the fluorescence signal for one mismatch and three mismatch was observed upon hybridization of probe with target DNAs, while there was no response for the random target ssDNA under the same experimental conditions. The intensity of fluorescence signal was linear to the concentration of target DNA ranging from 3.9×10−9 to 3.0×10−6molL−1. A detection limit of 1.22×10−9molL−1 of oligonucleotides can be estimated. The proposed hybridization assay is simple and possesses good analytical characteristics and it can provide an effective and efficient route in the development of DNA biosensors and biochips.
Keywords: Silica nanoparticles; Tetraethyl orthosilicate (TEOS); Immobilization; Single-stranded deoxyribonucleic acid (ssDNA); Hybridization
Simultaneous analysis of the photocatalytic degradation of polycyclic aromatic hydrocarbons using three-dimensional excitation–emission matrix fluorescence and parallel factor analysis by M.V. Bosco; M.P. Callao; M.S. Larrechi (pp. 184-191).
Polycyclic aromatic hydrocarbons (PAHs) may be photochemically degraded. Monitoring of degradation process of PAHs is carried out by traditional methods, which normally imply time-consuming procedures that do not allow the chemical process to be analyzed in real time. In the present study, photodegradation kinetics of dibenz[a,h]anthracene, benz[a]anthracene, benz[a]pyrene and benz[k]fluorantene were investigated in aqueous solutions under different conditions. A 23 factorial design was used for optimizing the degradation process.Fluorescence spectroscopy is a fast, cheap and sensitive analytical method, attractive for use in conjunction with chemometric methods; in this case three-way analytical methodology based on fluorescence excitation–emission matrix (EEM) and parallel factor analysis (PARAFAC) was employed. A four-factor PARAFAC model made it possible to resolve the species presents in the degradation mixture and quantify the relative concentration of the analytes throughout the degradation. Several different parameters, such as core consistency, percentage of fit and correlation coefficients between recovered and reference spectra were employed to determine the suitable number of factors for the PARAFAC model. This new methodology allows us to determine satisfactorily the PAHs concentration during the photodegradation in mixtures of arbitrary composition, representing an interesting alternative to the conventional techniques normally used for the monitoring of degradation reactions.
Keywords: Polycyclic aromatic hydrocarbons; Parallel factor analysis model; Photodegradation; Optimization; Excitation–emission matrix
Simultaneous analysis of the photocatalytic degradation of polycyclic aromatic hydrocarbons using three-dimensional excitation–emission matrix fluorescence and parallel factor analysis by M.V. Bosco; M.P. Callao; M.S. Larrechi (pp. 184-191).
Polycyclic aromatic hydrocarbons (PAHs) may be photochemically degraded. Monitoring of degradation process of PAHs is carried out by traditional methods, which normally imply time-consuming procedures that do not allow the chemical process to be analyzed in real time. In the present study, photodegradation kinetics of dibenz[a,h]anthracene, benz[a]anthracene, benz[a]pyrene and benz[k]fluorantene were investigated in aqueous solutions under different conditions. A 23 factorial design was used for optimizing the degradation process.Fluorescence spectroscopy is a fast, cheap and sensitive analytical method, attractive for use in conjunction with chemometric methods; in this case three-way analytical methodology based on fluorescence excitation–emission matrix (EEM) and parallel factor analysis (PARAFAC) was employed. A four-factor PARAFAC model made it possible to resolve the species presents in the degradation mixture and quantify the relative concentration of the analytes throughout the degradation. Several different parameters, such as core consistency, percentage of fit and correlation coefficients between recovered and reference spectra were employed to determine the suitable number of factors for the PARAFAC model. This new methodology allows us to determine satisfactorily the PAHs concentration during the photodegradation in mixtures of arbitrary composition, representing an interesting alternative to the conventional techniques normally used for the monitoring of degradation reactions.
Keywords: Polycyclic aromatic hydrocarbons; Parallel factor analysis model; Photodegradation; Optimization; Excitation–emission matrix
Investigation on sensitized chemiluminescence systems and their mechanism for five fluoroquinolones by Hanwen Sun; Liqing Li; Xueyan Chen (pp. 192-199).
The novel chemiluminescence (CL) reaction systems were established for lomefloxacin (LMFX), ofloxacin(OFLX), norfloxacin (NFLX), gatifloxacin (GAFX) and enoxacin (ENX). The sensitized CL emission mechanism was investigated for the five systems by comparing the fluorescence emission with CL spectra. For LMFX–Ce(IV)–S2O32−–H2SO4 and OFLX–Ce(IV)–S2O42−–H2SO4 systems, the CL intensity is enhanced through intermolecular energy transfer from the excited SO2* to LMFX and OFLX. For NFLX–Ce(IV)–S2O42−–HNO3 system, the sensitized CL is based on intermolecular energy transfer from the excited SO2* to NFLX oxide. For Eu3+–GAFX–Ce(IV)–S2O42−–HCl and Dy3+–ENX–Ce(IV)–S2O32−–H2SO4 systems, the CL spectra are from the narrow characteristic emission at 590, 619 and 649nm of Eu3+* (5D0→7F1,5D0→7F2,5D0→7F3) and at 482 and 578nm of Dy3+ (4F9→6H15/2,4F9→6H13/2) through intermolecular energy transfer from the excited SO2* to GAFX and ENX, followed by intramolecular energy transfer from GAFX* to Eu3+ and ENX* to Dy3+. The conditions of CL emission were investigated and optimized. The proposed five enhanced CL systems have good linearity, higher sensitivity, precision and potential capability for residue analysis of studied analytes in foods and biological samples.
Keywords: Sensitized CL systems; Mechanism; Lomefloxacin; Ofloxacin; Norfloxacin; Gatifloxacin; Enoxacin
Investigation on sensitized chemiluminescence systems and their mechanism for five fluoroquinolones by Hanwen Sun; Liqing Li; Xueyan Chen (pp. 192-199).
The novel chemiluminescence (CL) reaction systems were established for lomefloxacin (LMFX), ofloxacin(OFLX), norfloxacin (NFLX), gatifloxacin (GAFX) and enoxacin (ENX). The sensitized CL emission mechanism was investigated for the five systems by comparing the fluorescence emission with CL spectra. For LMFX–Ce(IV)–S2O32−–H2SO4 and OFLX–Ce(IV)–S2O42−–H2SO4 systems, the CL intensity is enhanced through intermolecular energy transfer from the excited SO2* to LMFX and OFLX. For NFLX–Ce(IV)–S2O42−–HNO3 system, the sensitized CL is based on intermolecular energy transfer from the excited SO2* to NFLX oxide. For Eu3+–GAFX–Ce(IV)–S2O42−–HCl and Dy3+–ENX–Ce(IV)–S2O32−–H2SO4 systems, the CL spectra are from the narrow characteristic emission at 590, 619 and 649nm of Eu3+* (5D0→7F1,5D0→7F2,5D0→7F3) and at 482 and 578nm of Dy3+ (4F9→6H15/2,4F9→6H13/2) through intermolecular energy transfer from the excited SO2* to GAFX and ENX, followed by intramolecular energy transfer from GAFX* to Eu3+ and ENX* to Dy3+. The conditions of CL emission were investigated and optimized. The proposed five enhanced CL systems have good linearity, higher sensitivity, precision and potential capability for residue analysis of studied analytes in foods and biological samples.
Keywords: Sensitized CL systems; Mechanism; Lomefloxacin; Ofloxacin; Norfloxacin; Gatifloxacin; Enoxacin
Leachability and analytical speciation of antimony in coal fly ash by Ricard Miravet; José Fermín López-Sánchez; Roser Rubio (pp. 200-206).
The present study assesses the single extraction of Sb from two coal fly ashes with aqueous solutions at a range of pHs (1–12) and with citrate 1molL−1 at pH 5, in order to obtain preliminary information about Sb leaching from this matrix. Speciation analysis of the coal fly ash extracts by HPLC-ICP-MS and HPLC-HG-AFS was carried out in order to identify the presence of individual Sb species. Sb(V) was the main Sb species in the leachates, although minor amounts of Sb(III) were also detected in some extracts. Citrate at pH 5 gave the best extraction efficiency for both samples whereas Sb species were also fairly soluble in aqueous solutions at acidic pHs. Analysis by HPLC-ICP-MS provided the most accurate results in some extracts (aqueous solution at pH 1 and citrate at pH 5) when both coupled techniques used were compared. The presence in these leachates of higher content of interfering metal ions (Ca, Fe and Pb) than those obtained for the Sb species reduced stibine generation in the HPLC-HG-AFS analysis. The proposed methodology can be considered reliable and useful for antimony speciation in environmental studies.
Keywords: Antimony speciation; Coal fly ash; Leachability; Hyphenated techniques
Leachability and analytical speciation of antimony in coal fly ash by Ricard Miravet; José Fermín López-Sánchez; Roser Rubio (pp. 200-206).
The present study assesses the single extraction of Sb from two coal fly ashes with aqueous solutions at a range of pHs (1–12) and with citrate 1molL−1 at pH 5, in order to obtain preliminary information about Sb leaching from this matrix. Speciation analysis of the coal fly ash extracts by HPLC-ICP-MS and HPLC-HG-AFS was carried out in order to identify the presence of individual Sb species. Sb(V) was the main Sb species in the leachates, although minor amounts of Sb(III) were also detected in some extracts. Citrate at pH 5 gave the best extraction efficiency for both samples whereas Sb species were also fairly soluble in aqueous solutions at acidic pHs. Analysis by HPLC-ICP-MS provided the most accurate results in some extracts (aqueous solution at pH 1 and citrate at pH 5) when both coupled techniques used were compared. The presence in these leachates of higher content of interfering metal ions (Ca, Fe and Pb) than those obtained for the Sb species reduced stibine generation in the HPLC-HG-AFS analysis. The proposed methodology can be considered reliable and useful for antimony speciation in environmental studies.
Keywords: Antimony speciation; Coal fly ash; Leachability; Hyphenated techniques
On-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry for the speciation of inorganic antimony in environmental and biological samples by Yingjie Li; Bin Hu; Zucheng Jiang (pp. 207-214).
A new method for the determination of inorganic Sb species by on-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) is presented and evaluated. The method is based on the complexation of Sb(III) with pyrrolidine dithiocarbamate (PDC) which form an hydrophobic complex at pH 5.5 and subsequently enter surfactant-rich phase at pH 5.5, whereas Sb(V) remained in aqueous solutions. The preconcentration step is mediated by micelles of the non-ionic surfactant Triton X-114 with ammonium pyrrolidine dithiocarbamate (APDC). The micellar system containing the complex was loaded into the FIA manifold at a flow rate of 2.5mLmin−1, and the surfactant-rich phase was retained in a microcolumn packed with absorbent cotton, at pH 5.5. After the surfactant-rich phase was eluted with 100μL acetonitrile, it was determined by ETV-ICP-AES. Sb(V) is reduced to Sb(III) byl-cysteine prior to determined total Sb, and its assay is based on subtracting Sb(III) from total antimony. The main factors affecting separation/preconcentration and the vaporization behavior of analyte in graphite tube were investigated in detail. Under the optimized conditions, the precision relative standard deviation (R.S.D.) for eight replicate measurements of 0.2μgmL−1 Sb(III) was 4.3%. The apparent concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for ETV-ICP-AES detection and in the initial solution, was 872 for Sb(III). The limit of detection (LOD) for Sb(III) was 0.09μgL−1. The proposed method was successfully applied for the speciation of inorganic antimony in different water samples and urine sample with satisfactory results.
Keywords: Inorganic antimony speciation; On-line cloud point extraction; Electrothermal vaporization inductively coupled plasma atomic emission spectrometry; Environmental and biological samples
On-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry for the speciation of inorganic antimony in environmental and biological samples by Yingjie Li; Bin Hu; Zucheng Jiang (pp. 207-214).
A new method for the determination of inorganic Sb species by on-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) is presented and evaluated. The method is based on the complexation of Sb(III) with pyrrolidine dithiocarbamate (PDC) which form an hydrophobic complex at pH 5.5 and subsequently enter surfactant-rich phase at pH 5.5, whereas Sb(V) remained in aqueous solutions. The preconcentration step is mediated by micelles of the non-ionic surfactant Triton X-114 with ammonium pyrrolidine dithiocarbamate (APDC). The micellar system containing the complex was loaded into the FIA manifold at a flow rate of 2.5mLmin−1, and the surfactant-rich phase was retained in a microcolumn packed with absorbent cotton, at pH 5.5. After the surfactant-rich phase was eluted with 100μL acetonitrile, it was determined by ETV-ICP-AES. Sb(V) is reduced to Sb(III) byl-cysteine prior to determined total Sb, and its assay is based on subtracting Sb(III) from total antimony. The main factors affecting separation/preconcentration and the vaporization behavior of analyte in graphite tube were investigated in detail. Under the optimized conditions, the precision relative standard deviation (R.S.D.) for eight replicate measurements of 0.2μgmL−1 Sb(III) was 4.3%. The apparent concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for ETV-ICP-AES detection and in the initial solution, was 872 for Sb(III). The limit of detection (LOD) for Sb(III) was 0.09μgL−1. The proposed method was successfully applied for the speciation of inorganic antimony in different water samples and urine sample with satisfactory results.
Keywords: Inorganic antimony speciation; On-line cloud point extraction; Electrothermal vaporization inductively coupled plasma atomic emission spectrometry; Environmental and biological samples
Mechanistic aspects of electrochemical hydride generation for cadmium by M.H. Arbab-Zavar; M. Chamsaz; A. Youssefi; M. Aliakbari (pp. 215-220).
The mechanistic aspects of a novel methodology for the electrochemical hydride generation (EcHG) of cadmium, entitled as the catholyte variation, have been studied. The hydrogen overvoltage of different cathode materials was determined in dilute electrolyte. The lead–tin alloy used as the cathode material for the EcHG of Cd had the highest hydrogen overpotential. In this technique, both electrolyte medium and cathode surface would change during electrolysis. The catholyte variation EcHG coupled with a flame heated quartz tube atomizer (QTA) atomic absorption spectrometer (AAS) produced peak-shaped transient signal of Cd. The analytical signal was significantly enhanced at neutralization time. The simultaneous production of lead and tin hydrides as well as the hydrogen at that time may speed up the desorption of cadmium species from the surface of the cathode. Also the high hydrogen overvoltage and the neutral medium aided the formation and separation of cadmium hydride molecules. The generated CdH2 vapour was kinetically stable.
Keywords: Cadmium; Cadmium hydride; Electrochemical hydride generation; Atomic absorption spectrometry
Mechanistic aspects of electrochemical hydride generation for cadmium by M.H. Arbab-Zavar; M. Chamsaz; A. Youssefi; M. Aliakbari (pp. 215-220).
The mechanistic aspects of a novel methodology for the electrochemical hydride generation (EcHG) of cadmium, entitled as the catholyte variation, have been studied. The hydrogen overvoltage of different cathode materials was determined in dilute electrolyte. The lead–tin alloy used as the cathode material for the EcHG of Cd had the highest hydrogen overpotential. In this technique, both electrolyte medium and cathode surface would change during electrolysis. The catholyte variation EcHG coupled with a flame heated quartz tube atomizer (QTA) atomic absorption spectrometer (AAS) produced peak-shaped transient signal of Cd. The analytical signal was significantly enhanced at neutralization time. The simultaneous production of lead and tin hydrides as well as the hydrogen at that time may speed up the desorption of cadmium species from the surface of the cathode. Also the high hydrogen overvoltage and the neutral medium aided the formation and separation of cadmium hydride molecules. The generated CdH2 vapour was kinetically stable.
Keywords: Cadmium; Cadmium hydride; Electrochemical hydride generation; Atomic absorption spectrometry
Comparison of liquid–liquid extraction, solid-phase extraction and co-precipitation preconcentration methods for the determination of cadmium, copper, nickel, lead and zinc in seawater by Irina Komjarova; Ronny Blust (pp. 221-228).
Three major types of pre-concentration methods were evaluated and optimised for the extraction and determination of Cd, Cu, Ni, Pb and Zn from seawater samples. The traditional APDC/DDDC-Freon liquid–liquid extraction method showed excellent results for a multi-elemental analysis. However, the technique is labour consuming, very sensitive to operational conditions, employs environmentally unsafe and expensive solvents and requires large sample volumes. In the solid phase extraction method, the performances of a traditional Amberlite XAD-4 and a novel Dowex Optipore V-493 were evaluated. Application of Dowex Optipore V-493 resin provided better results at low concentrations than the generally used Amberlite XAD-4 resin using low sample volumes. However, the presence of natural organic compounds may decrease extraction efficiency of both resins for Cu. Thus, a pre-treatment with UV irradiation is advantageous for samples with high organic content. Cobalt co-precipitation methods showed good Cu and Ni recoveries, but gave poor results for Cd at low concentrations. In addition, high sample volumes are required. Both solid phase and co-precipitation methods showed unsatisfactory results in determination of Pb. Finally, a summary of methods advantages are given for choosing the most suitable method.
Keywords: Analytical methods; Trace metals; Seawater; Atomic absorption; Electrothermal; Spectrometry; Preconcentration; Optimisation
Comparison of liquid–liquid extraction, solid-phase extraction and co-precipitation preconcentration methods for the determination of cadmium, copper, nickel, lead and zinc in seawater by Irina Komjarova; Ronny Blust (pp. 221-228).
Three major types of pre-concentration methods were evaluated and optimised for the extraction and determination of Cd, Cu, Ni, Pb and Zn from seawater samples. The traditional APDC/DDDC-Freon liquid–liquid extraction method showed excellent results for a multi-elemental analysis. However, the technique is labour consuming, very sensitive to operational conditions, employs environmentally unsafe and expensive solvents and requires large sample volumes. In the solid phase extraction method, the performances of a traditional Amberlite XAD-4 and a novel Dowex Optipore V-493 were evaluated. Application of Dowex Optipore V-493 resin provided better results at low concentrations than the generally used Amberlite XAD-4 resin using low sample volumes. However, the presence of natural organic compounds may decrease extraction efficiency of both resins for Cu. Thus, a pre-treatment with UV irradiation is advantageous for samples with high organic content. Cobalt co-precipitation methods showed good Cu and Ni recoveries, but gave poor results for Cd at low concentrations. In addition, high sample volumes are required. Both solid phase and co-precipitation methods showed unsatisfactory results in determination of Pb. Finally, a summary of methods advantages are given for choosing the most suitable method.
Keywords: Analytical methods; Trace metals; Seawater; Atomic absorption; Electrothermal; Spectrometry; Preconcentration; Optimisation
Heteroscedasticity of retention factor and adequate modeling in micellar liquid chromatography by Alexander P. Boichenko; Anna L. Iwashchenko; Lidia P. Loginova; Artem U. Kulikov (pp. 229-238).
The two concepts of micelle formation (pseudo-phase and mass-action) could be the basis of retention models in micellar liquid chromatography (MLC). The separation of 4-hydroxybenzoic acid esters and seven polyaromatic hydrocarbons were performed to study the repeatability of retention factor in MLC. The full two factor experimental design was used for studying the dependence of retention factor variance on mobile phase composition (sodium dodecylsulfate, 1-butanol). The experimentally observed heteroscedasticity and perturbations after linearization were taken into account by using statistical weights obtained on the basis of errors propagation law and the modeling of retention by non-weighted and weighted least squares method was performed. The mechanistical retention models based on pseudo-phase and mass-action concepts of micelle formation were compared by fitting quality and prediction capability and high robustness of bilogarithmic dependence was observed. The significance of retention factor heteroscedasticity for retention hydrophobicity relationships was shown.
Keywords: Micellar liquid chromatography; Heteroscedasticity; Statistical weights; Retention modeling; Retention hydrophobicity relationships
Heteroscedasticity of retention factor and adequate modeling in micellar liquid chromatography by Alexander P. Boichenko; Anna L. Iwashchenko; Lidia P. Loginova; Artem U. Kulikov (pp. 229-238).
The two concepts of micelle formation (pseudo-phase and mass-action) could be the basis of retention models in micellar liquid chromatography (MLC). The separation of 4-hydroxybenzoic acid esters and seven polyaromatic hydrocarbons were performed to study the repeatability of retention factor in MLC. The full two factor experimental design was used for studying the dependence of retention factor variance on mobile phase composition (sodium dodecylsulfate, 1-butanol). The experimentally observed heteroscedasticity and perturbations after linearization were taken into account by using statistical weights obtained on the basis of errors propagation law and the modeling of retention by non-weighted and weighted least squares method was performed. The mechanistical retention models based on pseudo-phase and mass-action concepts of micelle formation were compared by fitting quality and prediction capability and high robustness of bilogarithmic dependence was observed. The significance of retention factor heteroscedasticity for retention hydrophobicity relationships was shown.
Keywords: Micellar liquid chromatography; Heteroscedasticity; Statistical weights; Retention modeling; Retention hydrophobicity relationships
An improved method to detect ethyl glucuronide in urine using reversed-phase liquid chromatography and pulsed electrochemical detection by Romina Shah; William R. LaCourse (pp. 239-245).
Pulsed electrochemical detection (PED) following reversed-phase liquid chromatography (LC) has been applied recently to the detection of ethyl glucuronide (EtG) in the urine of live and deceased individuals. In this paper, several key improvements to the method are made to enhance sensitivity, reproducibility, and accuracy. These improvements include (i) further optimization of the sample preparation procedure that has increased the recovery from ca. 50% to 84±3% in synthetic urine matrix; (ii) changing the internal standard from methyl glucuronide (MetG) to propyl glucuronide (ProG), which does not elute within the interference of the matrix; and (iii) altering the mobile phase of the separation from acetonitrile to t-butanol to virtually eliminate signal suppression in PED. As a consequence, detection limits have been reduced to 0.01μgmL−1, reproducibility has been improved by a factor of two, and sample size has been reduced five-fold. Blind studies in synthetic urine showed no significant difference between the amount recovered and the true value determined at the 95% confidence level for all samples. Importantly, PED requires no derivatization, and it can detect virtually all glucuronides.
Keywords: Biomarker; Ethanol; Glucuronide; Pulsed electrochemical detection; Urine
An improved method to detect ethyl glucuronide in urine using reversed-phase liquid chromatography and pulsed electrochemical detection by Romina Shah; William R. LaCourse (pp. 239-245).
Pulsed electrochemical detection (PED) following reversed-phase liquid chromatography (LC) has been applied recently to the detection of ethyl glucuronide (EtG) in the urine of live and deceased individuals. In this paper, several key improvements to the method are made to enhance sensitivity, reproducibility, and accuracy. These improvements include (i) further optimization of the sample preparation procedure that has increased the recovery from ca. 50% to 84±3% in synthetic urine matrix; (ii) changing the internal standard from methyl glucuronide (MetG) to propyl glucuronide (ProG), which does not elute within the interference of the matrix; and (iii) altering the mobile phase of the separation from acetonitrile to t-butanol to virtually eliminate signal suppression in PED. As a consequence, detection limits have been reduced to 0.01μgmL−1, reproducibility has been improved by a factor of two, and sample size has been reduced five-fold. Blind studies in synthetic urine showed no significant difference between the amount recovered and the true value determined at the 95% confidence level for all samples. Importantly, PED requires no derivatization, and it can detect virtually all glucuronides.
Keywords: Biomarker; Ethanol; Glucuronide; Pulsed electrochemical detection; Urine
Determination of cefuroxime axetil in tablets and biological fluids using liquid chromatography and flow injection analysis by Nafiz Ö. Can; Göksel Altiokka; Hassan Y. Aboul-Enein (pp. 246-252).
Cefuroxime axetil is the pro-drug of cephalosporin cefuroxime that is used in the treatment of common community-acquired infections. A simple and precise liquid chromatographic method for the determination of cefuroxime axetil in pharmaceutical tablets, human serum and urine has been developed and validated. Cefuroxime axetil and indapamide (internal standard) were separated by a reversed phase column (Supelco Hypersil 5μm, 150mm×4.6mm i.d., C18) using a mobile phase consisting of KH2PO4 (0.1M) and acetonitrile (70:30v/v) (at pH 4.0). The mobile phase was pumped at 1.0mLmin−1 flow rate and cefuroxime axetil was detected by ultraviolet detection at 281nm within an average analysis time of 11min. Flow injection analysis was performed for pharmaceutical tablet analysis using a carrier stream of methanol:water (10:90v/v) with a flow rate of 1.0mLmin−1. The LOD and LOQ concentrations of the HPLC method were 1.35×10−7 and 4.08×10−7M for the HPLC analysis and 1.31×10−7 and 4.00×10−7M for FIA. The results of the analysis of the tablet formulation obtained by using these methods were statistically comparable with each other and with an additional spectrophotometric method. There was no significant difference between all these methods.
Keywords: Cefuroxime; Pharmaceutical analysis; Biological fluids; Flow injection analysis; High performance liquid chromatography (HPLC) analysis
Determination of cefuroxime axetil in tablets and biological fluids using liquid chromatography and flow injection analysis by Nafiz Ö. Can; Göksel Altiokka; Hassan Y. Aboul-Enein (pp. 246-252).
Cefuroxime axetil is the pro-drug of cephalosporin cefuroxime that is used in the treatment of common community-acquired infections. A simple and precise liquid chromatographic method for the determination of cefuroxime axetil in pharmaceutical tablets, human serum and urine has been developed and validated. Cefuroxime axetil and indapamide (internal standard) were separated by a reversed phase column (Supelco Hypersil 5μm, 150mm×4.6mm i.d., C18) using a mobile phase consisting of KH2PO4 (0.1M) and acetonitrile (70:30v/v) (at pH 4.0). The mobile phase was pumped at 1.0mLmin−1 flow rate and cefuroxime axetil was detected by ultraviolet detection at 281nm within an average analysis time of 11min. Flow injection analysis was performed for pharmaceutical tablet analysis using a carrier stream of methanol:water (10:90v/v) with a flow rate of 1.0mLmin−1. The LOD and LOQ concentrations of the HPLC method were 1.35×10−7 and 4.08×10−7M for the HPLC analysis and 1.31×10−7 and 4.00×10−7M for FIA. The results of the analysis of the tablet formulation obtained by using these methods were statistically comparable with each other and with an additional spectrophotometric method. There was no significant difference between all these methods.
Keywords: Cefuroxime; Pharmaceutical analysis; Biological fluids; Flow injection analysis; High performance liquid chromatography (HPLC) analysis
Stability indicating high-performance thin-layer chromatographic determination of gatifloxacin as bulk drug and from polymeric nanoparticles by Sanjay K. Motwani; Roop K. Khar; Farhan J. Ahmad; Shruti Chopra; K. Kohli; Sushma Talegaonkar; Zeenat Iqbal (pp. 253-260).
A simple, sensitive, selective, precise and stability indicating high-performance thin-layer chromatographic method for determination of gatifloxacin both as a bulk drug and from polymeric nanoparticles was developed and validated as per the International Conference on Harmonization (ICH) guidelines. The method employed thin-layer chromatography (TLC) aluminium plates precoated with silica gel 60F-254 as the stationary phase and the mobile phase consisted of n-propanol–methanol-concentrated ammonia solution (25%) (5:1:0.9, v/v/v). This solvent system was found to give compact spots for gatifloxacin ( Rf value of 0.60±0.02). Densitometric analysis of gatifloxacin was carried out in the absorbance mode at 292nm. The linear regression analysis data for the calibration plots showed good linear relationship with r=0.9953 with respect to peak area in the concentration range of 400–1200ngspot−1. The mean value (±S.D.) of slope and intercept were 9.66±0.05 and 956.33±27.67, respectively. The method was validated for precision, accuracy, ruggedness and recovery. The limits of detection and quantitation were 2.73 and 8.27ngspot−1, respectively. Gatifloxacin was subjected to acid and alkali hydrolysis, oxidation, photodegradation and dry heat treatment. The drug undergoes degradation under acidic and basic conditions and upon wet and dry heat treatment. The degraded products were well separated from the pure drug. The statistical analysis proves that the developed method for quantification of gatifloxacin as bulk drug and from polymeric nanoparticles is reproducible and selective. As the method could effectively separate the drug from its degradation products, it can be employed as stability-indicating one.
Keywords: Gatifloxacin; High-performance thin-layer chromatography; Stability indicating; Stress degradation; Validation
Stability indicating high-performance thin-layer chromatographic determination of gatifloxacin as bulk drug and from polymeric nanoparticles by Sanjay K. Motwani; Roop K. Khar; Farhan J. Ahmad; Shruti Chopra; K. Kohli; Sushma Talegaonkar; Zeenat Iqbal (pp. 253-260).
A simple, sensitive, selective, precise and stability indicating high-performance thin-layer chromatographic method for determination of gatifloxacin both as a bulk drug and from polymeric nanoparticles was developed and validated as per the International Conference on Harmonization (ICH) guidelines. The method employed thin-layer chromatography (TLC) aluminium plates precoated with silica gel 60F-254 as the stationary phase and the mobile phase consisted of n-propanol–methanol-concentrated ammonia solution (25%) (5:1:0.9, v/v/v). This solvent system was found to give compact spots for gatifloxacin ( Rf value of 0.60±0.02). Densitometric analysis of gatifloxacin was carried out in the absorbance mode at 292nm. The linear regression analysis data for the calibration plots showed good linear relationship with r=0.9953 with respect to peak area in the concentration range of 400–1200ngspot−1. The mean value (±S.D.) of slope and intercept were 9.66±0.05 and 956.33±27.67, respectively. The method was validated for precision, accuracy, ruggedness and recovery. The limits of detection and quantitation were 2.73 and 8.27ngspot−1, respectively. Gatifloxacin was subjected to acid and alkali hydrolysis, oxidation, photodegradation and dry heat treatment. The drug undergoes degradation under acidic and basic conditions and upon wet and dry heat treatment. The degraded products were well separated from the pure drug. The statistical analysis proves that the developed method for quantification of gatifloxacin as bulk drug and from polymeric nanoparticles is reproducible and selective. As the method could effectively separate the drug from its degradation products, it can be employed as stability-indicating one.
Keywords: Gatifloxacin; High-performance thin-layer chromatography; Stability indicating; Stress degradation; Validation
Novel catalytic oxidative coupling reaction of N,N-dimethyl- p-phenylenediamine with 1,3-phenylenediamine and its applications to the determination of copper and iron at trace levels by flow injection technique by S. Lunvongsa; T. Takayanagi; M. Oshima; S. Motomizu (pp. 261-269).
A new catalytic oxidative coupling reaction of N,N-dimethyl- p-phenylenediamine (DPD) with 1,3-phenylenediamine (mPD) in the presence of hydrogen peroxide has been developed for trace metals analysis. The rate of the oxidation/coupling reaction can be enhanced significantly by iron, copper and cobalt. These metal ions can catalyze the oxidation reaction of DPD to form an oxidized product; the oxidized DPD was then coupled with mPD to give a blue-colored product which was measured spectrophotometrically at 650nm. On the basis of such a reaction scheme, two simple flow injection analysis methods for the determination of copper and iron have been developed. Detailed studies on chemical and FIA variables affecting the sensitivity of the detection were carried out. Interferences from several ionic species were examined for the determination of copper: the interference effect by Fe(III) and Fe(II) up to 1.5mgL−1 was successfully suppressed by pretreating sample with ammonium acetate buffer solution (pH 8.4). Good linearity of a standard calibration graph was obtained over the ranges of 0–8 and 0–2μgL−1 of copper and iron, respectively, and the detection limits were 0.05 and 0.02μgL−1 for copper and iron, respectively. The precision of the methods in terms of relative standard deviation were 1.4 and 1.5% of R.S.D. which were obtained from 10 injections of 2.0 and 1.0μgL−1 of standard copper and iron, respectively. The proposed methods were successfully applied to the determination of copper and iron in tap and river water samples. The accuracy of the proposed methods was assessed by the analysis of certified reference material of river water.
Keywords: Copper; Iron; Flow injection analysis; Coupling reaction; N,N; -dimethyl-; p; -phenylenediamine
Novel catalytic oxidative coupling reaction of N,N-dimethyl- p-phenylenediamine with 1,3-phenylenediamine and its applications to the determination of copper and iron at trace levels by flow injection technique by S. Lunvongsa; T. Takayanagi; M. Oshima; S. Motomizu (pp. 261-269).
A new catalytic oxidative coupling reaction of N,N-dimethyl- p-phenylenediamine (DPD) with 1,3-phenylenediamine (mPD) in the presence of hydrogen peroxide has been developed for trace metals analysis. The rate of the oxidation/coupling reaction can be enhanced significantly by iron, copper and cobalt. These metal ions can catalyze the oxidation reaction of DPD to form an oxidized product; the oxidized DPD was then coupled with mPD to give a blue-colored product which was measured spectrophotometrically at 650nm. On the basis of such a reaction scheme, two simple flow injection analysis methods for the determination of copper and iron have been developed. Detailed studies on chemical and FIA variables affecting the sensitivity of the detection were carried out. Interferences from several ionic species were examined for the determination of copper: the interference effect by Fe(III) and Fe(II) up to 1.5mgL−1 was successfully suppressed by pretreating sample with ammonium acetate buffer solution (pH 8.4). Good linearity of a standard calibration graph was obtained over the ranges of 0–8 and 0–2μgL−1 of copper and iron, respectively, and the detection limits were 0.05 and 0.02μgL−1 for copper and iron, respectively. The precision of the methods in terms of relative standard deviation were 1.4 and 1.5% of R.S.D. which were obtained from 10 injections of 2.0 and 1.0μgL−1 of standard copper and iron, respectively. The proposed methods were successfully applied to the determination of copper and iron in tap and river water samples. The accuracy of the proposed methods was assessed by the analysis of certified reference material of river water.
Keywords: Copper; Iron; Flow injection analysis; Coupling reaction; N,N; -dimethyl-; p; -phenylenediamine
Flow-injection methylene blue-based spectrophotometric method for the determination of peroxide values in edible oils by Anissa Dhaouadi; Lotfi Monser; Saloua Sadok; Nafaâ Adhoum (pp. 270-274).
A flow-injection method for measuring the peroxide value (PV, mequiv. O2kg−1) in edible oils is described. The technique is based on spectrophotometric monitoring at 660nm of methylene blue (MB), generated from leucomethylene blue (LMB) oxidation with peroxides present in oil samples. After being optimized, the method was validated in terms of linearity, precision sensitivity and recovery.Linear calibration graph was obtained in the range 0.1–5mequiv. O2kg−1, with a detection limit ( S/ N=3) of 0.014mequiv. O2kg−1. The precision of the method (R.S.D., n=9) for within and between-days is better than 1.5% and 2.2%, respectively at 0.4mequiv. O2kg−1. The method was applied successfully to the determination of PV in six edible oil samples, and compared to the classical official method. Using the linear regression test, Student's t-test and variance ratio F-test, there was no significant difference between the compared methods. The proposed method is accurate, simple, cheap and could be used to control edible oil rancidity with a high sample throughputs (30 samples h−1).
Keywords: Edible oils; Flow injection; Methylene blue; Peroxide value
Flow-injection methylene blue-based spectrophotometric method for the determination of peroxide values in edible oils by Anissa Dhaouadi; Lotfi Monser; Saloua Sadok; Nafaâ Adhoum (pp. 270-274).
A flow-injection method for measuring the peroxide value (PV, mequiv. O2kg−1) in edible oils is described. The technique is based on spectrophotometric monitoring at 660nm of methylene blue (MB), generated from leucomethylene blue (LMB) oxidation with peroxides present in oil samples. After being optimized, the method was validated in terms of linearity, precision sensitivity and recovery.Linear calibration graph was obtained in the range 0.1–5mequiv. O2kg−1, with a detection limit ( S/ N=3) of 0.014mequiv. O2kg−1. The precision of the method (R.S.D., n=9) for within and between-days is better than 1.5% and 2.2%, respectively at 0.4mequiv. O2kg−1. The method was applied successfully to the determination of PV in six edible oil samples, and compared to the classical official method. Using the linear regression test, Student's t-test and variance ratio F-test, there was no significant difference between the compared methods. The proposed method is accurate, simple, cheap and could be used to control edible oil rancidity with a high sample throughputs (30 samples h−1).
Keywords: Edible oils; Flow injection; Methylene blue; Peroxide value
Application of 8-amino- N-(2-hydroxybenzylidene)naphthyl amine as a neutral ionophore in the construction of a lanthanum ion-selective sensor by M.R. Ganjali; P. Norouzi; T. Alizadeh; M. Adib (pp. 275-282).
In this work, a novel La(III) membrane sensor based on 8-amino- N-(2-hydroxybenzylidene)naphthylamine (AIP) is presented. This electrode reveals good selectivity for La3+ over a wide variety of lanthanides metal ions. Theoretical calculations and conductance study of AIP to lanthanum and some other metal ions were carried out and confirmed selectivity toward La(III) ions. The electrode comprises 7% AIP, 30% PVC, 61% NPOE and 2% KTpClPB. The sensor displays a linear dynamic range between 1.0×10−7 and 1.0×10−1M, with a nice Nernstian slope of 20.3±0.3mV per decade and a detection limit of 8.0×10−8M. The potentiometric response is independent of pH in the range of 4.0–9.0. The proposed sensor posses the advantage of short response time, and especially, very good selectivity towards a large number of cations, such as Sm(III), Ce(III, Pr(III), Yb(III) and Hg(II), low detection limit and wide linear dynamic range in comparison with former ones. The electrode can be used for at least seven weeks without any considerable divergence in the potentials. It was used as an indicator electrode in the potentiometric titration of La(III) ions with EDTA. The sensor was applied to the determination of La(III) ions concentration in binary mixtures. It was also applied for the determination of fluoride ions in mouth wash preparations.
Keywords: Lanthanum ions; 8-Amino-; N; -(2-hydroxybenzylidene)naphthylamine; Potentiometric sensor
Application of 8-amino- N-(2-hydroxybenzylidene)naphthyl amine as a neutral ionophore in the construction of a lanthanum ion-selective sensor by M.R. Ganjali; P. Norouzi; T. Alizadeh; M. Adib (pp. 275-282).
In this work, a novel La(III) membrane sensor based on 8-amino- N-(2-hydroxybenzylidene)naphthylamine (AIP) is presented. This electrode reveals good selectivity for La3+ over a wide variety of lanthanides metal ions. Theoretical calculations and conductance study of AIP to lanthanum and some other metal ions were carried out and confirmed selectivity toward La(III) ions. The electrode comprises 7% AIP, 30% PVC, 61% NPOE and 2% KTpClPB. The sensor displays a linear dynamic range between 1.0×10−7 and 1.0×10−1M, with a nice Nernstian slope of 20.3±0.3mV per decade and a detection limit of 8.0×10−8M. The potentiometric response is independent of pH in the range of 4.0–9.0. The proposed sensor posses the advantage of short response time, and especially, very good selectivity towards a large number of cations, such as Sm(III), Ce(III, Pr(III), Yb(III) and Hg(II), low detection limit and wide linear dynamic range in comparison with former ones. The electrode can be used for at least seven weeks without any considerable divergence in the potentials. It was used as an indicator electrode in the potentiometric titration of La(III) ions with EDTA. The sensor was applied to the determination of La(III) ions concentration in binary mixtures. It was also applied for the determination of fluoride ions in mouth wash preparations.
Keywords: Lanthanum ions; 8-Amino-; N; -(2-hydroxybenzylidene)naphthylamine; Potentiometric sensor
Polymer-coated bismuth film electrodes for the determination of trace metals by sequential-injection analysis/anodic stripping voltammetry by Georgia Kefala; Anastasios Economou (pp. 283-289).
In this work, the utility of polymer-coated bismuth film electrodes (BiFEs) was assessed for the simultaneous on-line determination of Cd(II), Pb(II) and Zn(II) by square-wave anodic stripping voltammetry (SWASV) in the sequential-injection analysis (SIA) mode. The polymeric Nafion coating was initially plated on a glassy carbon electrode forming part of the flow-through electrochemical cell. The subsequent steps of the bismuth layer generation, analyte preconcentration, voltammetric measurement and electrode cleaning were conducted on-line. For a sample volume of 1.2mL, the limits of detection (at S/N=3) were 2μgL−1 for Cd(II) and Pb(II) and 6μgL−1 for Zn(II), the coefficients of variation at 20μgL−1 were 5.1% for Cd(II), 5.9% for Pb(II) and 6.2% for Zn(II) and the measurement frequency was between 10 and 20h−1 (depending on the sample volume aspirated). It is demonstrated that the polymer-coated BiFEs, combined with SIA, can provide an environmentally friendly, sensitive and robust tool to perform rapid and cost-efficient on-line monitoring of trace metals by ASV, even in the presence of surface-active compounds.
Keywords: Sequential-injection analysis; Bismuth film electrodes; Trace metals; Nafion; Square-wave stripping voltammetry; Surfactants
Polymer-coated bismuth film electrodes for the determination of trace metals by sequential-injection analysis/anodic stripping voltammetry by Georgia Kefala; Anastasios Economou (pp. 283-289).
In this work, the utility of polymer-coated bismuth film electrodes (BiFEs) was assessed for the simultaneous on-line determination of Cd(II), Pb(II) and Zn(II) by square-wave anodic stripping voltammetry (SWASV) in the sequential-injection analysis (SIA) mode. The polymeric Nafion coating was initially plated on a glassy carbon electrode forming part of the flow-through electrochemical cell. The subsequent steps of the bismuth layer generation, analyte preconcentration, voltammetric measurement and electrode cleaning were conducted on-line. For a sample volume of 1.2mL, the limits of detection (at S/N=3) were 2μgL−1 for Cd(II) and Pb(II) and 6μgL−1 for Zn(II), the coefficients of variation at 20μgL−1 were 5.1% for Cd(II), 5.9% for Pb(II) and 6.2% for Zn(II) and the measurement frequency was between 10 and 20h−1 (depending on the sample volume aspirated). It is demonstrated that the polymer-coated BiFEs, combined with SIA, can provide an environmentally friendly, sensitive and robust tool to perform rapid and cost-efficient on-line monitoring of trace metals by ASV, even in the presence of surface-active compounds.
Keywords: Sequential-injection analysis; Bismuth film electrodes; Trace metals; Nafion; Square-wave stripping voltammetry; Surfactants
Monitoring of the insecticide trichlorfon by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy by Zahra Talebpour; Alireza Ghassempour; Mehdi Zendehzaban; Hamid Reza Bijanzadeh; Mohammad Hossein Mirjalili (pp. 290-296).
Trichlorfon is an organophosphorus insecticide, which is extensively being used for protection of fruit crops. Trichlorfon is a thermal labile compound, which cannot be easily determined by gas chromatography (GC) and has no suitable group for sensitive detection by high performance liquid chromatography (HPLC). In this study, a31P nuclear magnetic resonance (31P NMR) has been described for monitoring of trichlorfon without any separation step. The quantitative works of31P NMR spectroscopy has been performed in the presence of an internal standard (hexamethylphosphoramide). Limit of detection (LOD) for this method has been found to be 55mgL−1, without any sample preparation, and the linear working range was 150–5500mgL−1. Relative standard deviation (R.S.D.%) of the method for three replicates within and between days was obtained ≤9%. The average recovery efficiency was approximately 99–112%. This method was applied for monitoring trichlorfon in a commercial insecticide sample and tomato sample.
Keywords: Trichlorfon; Phosphorus-31 nuclear magnetic resonance (; 31; P NMR); Gas chromatography; High performance liquid chromatography
Monitoring of the insecticide trichlorfon by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy by Zahra Talebpour; Alireza Ghassempour; Mehdi Zendehzaban; Hamid Reza Bijanzadeh; Mohammad Hossein Mirjalili (pp. 290-296).
Trichlorfon is an organophosphorus insecticide, which is extensively being used for protection of fruit crops. Trichlorfon is a thermal labile compound, which cannot be easily determined by gas chromatography (GC) and has no suitable group for sensitive detection by high performance liquid chromatography (HPLC). In this study, a31P nuclear magnetic resonance (31P NMR) has been described for monitoring of trichlorfon without any separation step. The quantitative works of31P NMR spectroscopy has been performed in the presence of an internal standard (hexamethylphosphoramide). Limit of detection (LOD) for this method has been found to be 55mgL−1, without any sample preparation, and the linear working range was 150–5500mgL−1. Relative standard deviation (R.S.D.%) of the method for three replicates within and between days was obtained ≤9%. The average recovery efficiency was approximately 99–112%. This method was applied for monitoring trichlorfon in a commercial insecticide sample and tomato sample.
Keywords: Trichlorfon; Phosphorus-31 nuclear magnetic resonance (; 31; P NMR); Gas chromatography; High performance liquid chromatography