ISSN:0173-0835    

DOI:10.1002/elps.1150180202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

ISSN:0173-0835    

DOI:10.1002/elps.1150180203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractOnline interfacing of capillary electrophoresis (CE) with inductively coupled plasma‐mass spectrometry (ICP‐MS) has been accomplished using a laboratory‐made nebulizer. The high resolution of CE is used for the separations of Pt species of standard solutions and real samples, followed by ICP‐MS for element‐specific detection within 12 min. The samples are analyzed immediately after sample preparation or after 2–4 h of aging in order to elucidate undesired species transformations which may occur before analysis. The method was proven not to impair the species during the analytical procedure while being a necessary prerequisite to judge time‐dependent species transformations. Quality control aspects concerning species stability during the analytical procedure and stability of electrical current during nebulization were studied. A possibly interfering suction flow was estimated and found to be negligible. The results will serve as a basis for quality assurance in future investigations about Pt speci

ISSN:0173-0835    

DOI:10.1002/elps.1150180204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractBacterial‐facilitated depletion of cyanide is under development for remediation of heap leach operations in the gold mining industry. Capillary electrophoresis was found to be a powerful tool for quantifying cyanide depletion. Changes in cyanide concentration in aqueous suspensions ofPseudomonas alcaligenesbacteria and cyanide at eleveated pH were easily monitored by capillary electrophoresis. The resulting data can be used to study rates of cyanide depletion by this strain of bacteria. Concentrations of these bacteria at 105cells/mL were found to reduce cyanide from 100 ppm to less than 8 ppm in four days. In addition, other ions of interest in cyanide metabolism, such as formate, can be simultaneously analyzed. Direct UV detection of cyanide at 192 nm further simplifies the analytical method for these ion

ISSN:0173-0835    

DOI:10.1002/elps.1150180205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractThe instability of sulfonylureas in solution in methanol has led us to a kinetic study of methanolysis of two sulfonylureas using capillary electrophoresis. In a preliminary experiment, solutions of the seven compounds, bensulfuron methyl, sulfometuron methyl, nicosulfuron, chlorimuron ethyl, thifensulfuron methyl, metsulfuron methyl, and chlorsulfuron were prepared in methanol and in acetonitrile. After six weeks at room temperature the compounds dissolved in acetonitrile were quite stable as shown by electropherograms obtained with free zone capillary electrophoresis (CE). All seven of the compounds dissolved in methanol had undergone extensive degradation and in some cases the sulfonylurea could not be detected. Bensulfuron methyl and sulfometuron methyl were selected for further detailed study. Solutions of these two compounds in methanol were heated at 5, 40, 50, 57, and 65°C. No decomposition of either compound was observed in similar solutions of acetonitrile incubated at 57°C. The rates of decomposition in methanolic solutions were estimated from the decrease in instrumental response representing the peaks of the two sulfonylureas. The methanolysis of both compounds proceeded with pseudo first‐order kinetics as evidenced by the fact that semilogarithmic plots of the concentration of the substrate as a function of time were linear (correlation coefficients of 0.99). Rate constants and half‐lives for the reactions at 40, 50, 57, and 65°C were determined. These varied by factors of 18 to 22 depending upon the reaction temperature. The energies of activation for these reactions were estimated from the appropriate Arrhenius plots and found to be 26 kcal per mole for bensulfuron methyl and 24.5 kcal per mole for sulfometuron methyl. The kinetics of appearance of the products of methanolysis were directly related to and accurately predicted by the pseudo first‐order rate constants observed for disappearance of the sulfonylureas. Kinetic study of the reaction mixture by negative and positive‐ion mass spectrometry indicated that the products of methanolysis of sulfometuron methyl were 2‐carboxymethyl (N‐carboxymethyl)benzsulfonamide and 2‐amino‐4,6‐dimethyl pyrimidine and suggested a general mechanism for methanolysis of each of the sev

ISSN:0173-0835    

DOI:10.1002/elps.1150180206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractMicellar electrokinetic capillary chromatography (MEKC) was used to determine then‐octanol/water partition coefficient (Kow) of nonionic and ionic organic chemicals, mainly herbicides. Three electrolyte buffer systems with different organic modifiers were tested to evaluate their effect on the linear relationship between logKowand log ḱ. The effect of the pH value of injected samples on linear logKow/log ḱ relationship of ionic chemicals was also evaluated. Since a good correlation was found between logKowvalues and the logarithms of the capacity factor (ḱ) of each tested organic solvent, other parameters were considered to evaluate the efficacy of the method, such as the rate of electroosmotic flow, the efficiency and reproducibility of the separation, and the separation number (n). The method was found to be applicable over a range of logKowvalues from 0.72 to 5.1 and demonstrated a good predictive capability, giving similar results to direct experimental measures, at least within classes of compounds with similar physico‐chemical p

ISSN:0173-0835    

DOI:10.1002/elps.1150180207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractA novel chiral nonionic surfactant, namely octyl‐b‐D‐maltopyranoside (OM), was evaluated in chiral capillary electrophoresis of fluorescently labeled phenoxy acid herbicides. The labeling of the analytes with 7‐aminonaphthalene‐1,3‐disulfonic acid (ANDSA) permitted a concentration detection limit of 5 × 10−10Musing laser‐induced fluorescence detection. This limit of detection allowed the determination of ultradiluted solutions of the ANDSA‐derivatized phenoxy acid herbicides whose concentration was as low as 10−11M(i.e.2.2 ppt) by applying the concept of field‐amplified sample stacking (FASS). The sample injection by FASS did not adversely affect separation efficiencies, resolution and reproducibility of the electroporetic system. The tagging of the phenoxy acid herbicides with ANDSA increased the hydrophobicity of the analytes, thus favoring an enhanced solubilization of the derivatized herbicides in the OM micellar phase. The net results of this effect were a much shorter analysis time and an improved enantiomeric resolution of the derivatives when compared to underivatized phenoxy acid herbicides. The optimum surfactant concentration required for maximum resolution decreased with increasing hydrophobicity of the analyte, with the least hydrophobic analyte requiring higher surfactant concentration. Because of the two permanently charged sulfonic acid groups of the ANDSA tag, the pH of the running electrolyte had little effect on the enantiomeric resolution of the derivatized herbicides. Due to its salting‐out effect and increasing the micellized surfactant concentration, increasing the ionic strength of the running electrolyte increased the enantiomeric resolution of the least hydrophobic analytes. Conversely, increasing the percent methanol in the running electrolyte decreased the enantiomeric resolution of the least hydrophobic analytes due to decrease strength of solute‐micelle association. For hydrophobic analytes, existed an optimum percent of methanol existed for maxim

ISSN:0173-0835    

DOI:10.1002/elps.1150180208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractCapillary zone electrophoresis has been used for the enantiomeric separation of several herbicides. Different β‐cyclodextrin (CD) derivatives have been investigated for chiral separations and among them the negatively charged sulfobutyl ether β‐cyclodextrin (SBE‐β‐CD) proved to be effective for the stereoselective resolutions of the investigated herbicides. The effect of CD concentration, buffer pH and organic modifier on effective mobilities, resolution and selectivity of the analytes have been studied. Addition of SBE‐β‐CD (5–50 mg/mL) to the buffer at pH 9 resulted in a general increase of migration times as well as resolution. A CD concentration as low as 5 mg/mL was effective to completely resolve napropamide and ethofumesate enantiomers. Buffer solutions containing 40 mg/mL of SBE‐β‐CD were chosen to study the effect of buffer pH (7, 8, and 9) on chiral separation of the herbicides. No great differences in resolution and effective mobilities have been found in the pH 7–9 range. The addition of different organic modifiers to the background electrolyte at pH 9, containing 20 mg/mL of SBE‐β‐CD, showed different effects. Methanol was the most effective in improving resolution but in some cases total loss in enantiomeric separation was observed. The qualitative analysis of an enantiomerically pure herbicide (flamprop isopropyl) commerc

ISSN:0173-0835    

DOI:10.1002/elps.1150180209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractCapillary electrophoresis with ultraviolet detection (CE/UV) of selected fungicides (carbendazim, metalaxyl, propiconazole, and vinclozolin) using different buffer compositions was investigated. Capillary zone electrophoresis (CZE) with 10 mMsodium phosphate (pH 7.0) was not useful in separating the four fungicides used in this study. However, the four fungicides were well resolved by employing micellar electrokinetic capillary chromatography (MEKC). Among the two surfactants tested in MEKC, bile salts provided better separation compared to sodium dodecyl sulfate (SDS). A buffer consisting of 10 mMsodium phosphate with 100 mMsodium cholate and 10% methanol (pH 7.0) gave best results; excellent separation of the four compounds was achieved in less than 15 min. The CE/UV method was validated by analyzing deionized and lake‐water samples fortified with known concentrations of the four fungicides. Average recoveries of the fungicides in lake water at 4 μg/L level ranged from 42 to 8

ISSN:0173-0835    

DOI:10.1002/elps.1150180210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractA capillary electrophoresis (CE)‐indirect UV absorbance detection method for organotin compounds is described. The five triorganotin cations,viz., trimethyltin (TMT), triethyltin (TET), tripropyltin (TPT), tributyltin (TBT) and triphenyltin (TPhT), were efficiently separated by CE in 10 min with a 5 mMacetate buffer (pH 4.5) containing 3 mM4‐aminopyridine (4‐AP). 4‐AP also functioned as a UV‐absorbing coion for the indirect detection of these UV‐transparent organotin species. Simultaneous separation of di‐ and triorganotins was achieved with the addition of α‐cyclodextrin (α‐CD) as a modifier in the electrophoresis buffer. Linearity (r≥ 0.995) of about two orders of magnitude was generally obtained. The concentration limits of detection for the organotin compounds studied were between 2 and 20 μM(as tin). The relative standard deviation (RSD) values were in the range 1.3–7.1%. The applicability of the method for the analysis of mari

ISSN:0173-0835    

DOI:10.1002/elps.1150180211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY