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Characterization of chemical selectivity in micellar electrokinetic chromatography. 4. Effect of surfactant headgroup

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ANALYTICAL CHEMISTRY 1999年第7期71卷 1270-1277页

作者： Trone, MD Khaledi, MG N Carolina State Univ Dept Chem Raleigh NC 27695 USA

The influence of surfactant headgroups on migration behavior in micellar electrokinetic chromatography is examined. Using linear solvation energy relationships (LSER) and functional group selectivity studies, the effect of six anionic headgroups on chemical selectivity is characterized. The sodium dodecyl surfactants of the sulfate [SO4-], sulfonate [SO3-], carboxylate [CO2-], carbonyl valine [OC(O)NHCH(CH(CH3)(2))CO2-], and sulfoacetate [OC(O)CH2SO3-] anions are investigated. Solute size and the hydrogen-bond-donating ability of the micellar phase play the most significant roles in solute retention in all of the surfactants studied. While solute-micelle hydrogen bonding plays a dominant role in the observed selectivity, the dipolarity and polarizability of the micellar phase also have a small influence. The results also suggest that the hydrogen-bond-accepting ability for surfactants is inversely proportional to the proton acidity (pK(a)) of its headgroup, The observed hydrogen-bond-donating ability and dipolarity of surfactant systems are believed to be a result of the water that resides near the micelle surface.

关键词：色谱法胶束电动毛细管/方法氢键合表面活性剂/化学

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Congeneric behavior in estimations of octanol-water partition coefficients by micellar electrokinetic chromatography

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ANALYTICAL CHEMISTRY 2000年第6期72卷 1228-1235页

作者： Trone, MD Leonard, MS Khaledi, MG N Carolina State Univ Dept Chem Raleigh NC 27695 USA

Linear Solvation Energy Relationships (LSERs) are used to explain the congeneric behavior observed when using Micellar Electrokinetic Chromatography (MEKC) to estimate the octanol-water partition coefficient scale of solute hydrophobicity. Such studies provide useful insights about the nature of Solute interactions that are responsible for the sources of congeneric relationships between MEKC retention and log P-o/w. It was determined that solute dipolarity/polarizability and hydrogen-bonding character play the most important roles in the congeneric behavior observed for many surfactant systems. The individual dipolarity/polarizability and hydrogen-bonding contributions to the free energy of transfer were also investigated.

关键词：色谱法胶束电动毛细管/方法氢键合辛醇类/化学水/化学

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Simultaneous determination of sweeteners and preservatives in preserved fruits by micellar electrokinetic capillary chromatography

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JOURNAL OF CHROMATOGRAPHIC SCIENCE 2000年第8期38卷 345-352页

作者： Lin, YH Chou, SS Sheu, F Shyu, YT Natl Taiwan Univ Dept Hort Taipei 10660 Taiwan Natl Labs Foods & Drugs Dept Hlth Taipei Taiwan

A micellar electrokinetic capillary method for the simultaneous determination of the sweeteners dulcin, aspartame, saccharin, and acesulfame-K and the preservatives sorbic acid; benzoic acid; sodium dehydroacetate; and methyl-, ethyl-, propyl-, isopropyl-, butyl-, and isobutyl-p-hydroxybenzoate in preserved fruits is developed. These additives are ion-paired and extracted using sonication followed by solid-phase extraction from the sample. Separation is achieved using a 57-cm fused-silica capillary with a buffer comprised of 0.05M sodium deoxycholate, 0.02M borate-phosphate buffer (pH 8.6), and 5% acetonitrile, and the wavelength for detection is 214 nm. The average recovery rate for all sweeteners and preservatives is approximately 90% with good reproducibility, and the detection limits range from 10 to 25 μg/g. Fifty preserved fruit samples are analyzed for the content of sweeteners and preservatives. The sweeteners found in 28 samples was aspartame (0.17–11.59 g/kg) or saccharin (0.09–5.64 g/kg). Benzoic acid (0.02–1.72 g/kg) and sorbic acid (0.27–1.15 g/kg) were found as preservatives in 29 samples.

关键词：乙腈类缓冲剂色谱法胶束电动毛细管/方法食品保存食品防腐剂/分析水果/化学氢离子浓度甲醇甜味剂/分析

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Separation of urea, uric acid, creatine, and creatinine by micellar electrokinetic capillary chromatography with sodium cholate

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JOURNAL OF CHROMATOGRAPHIC SCIENCE 1999年第2期37卷 45-50页

作者： Yan, SL Lin, PZ Hsiao, MW Chung Shan Med & Dent Coll Dept Med Technol Taichung 40203 Taiwan

The capillary electrophoretic separation of the four nonprotein nitrogenous compounds (NPNs; urea, uric acid, creatine, and creatinine) typically employed in clinical and medical settings for the monitoring of renal function is described. Successful resolution of these compounds is achieved with the use of a bile salt micelle system composed of sodium cholate at phosphate buffer pH 7.4. The elution patterns of four NPNs are obtained within 30 min with a voltage of 30 kV. The effect of varying the applied voltage, temperature, and the mole ratio of phosphate buffer with bile salt surfactant on the migration behavior is also examined.

关键词：色谱法胶束电动毛细管/方法肌酸/分离和提纯肌酸酐/分离和提纯胆酸钠/化学温度尿素/分离和提纯尿酸/分离和提纯

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Determination of regularly distributed plant protectants in raw and drinking waters, using a multiresidue method with cyclodextrin-modified micellar electrokinetic chromatography

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JOURNAL OF AOAC INTERNATIONAL 1999年第6期82卷 1510-1522页

作者： Stutz, H Malissa, H Salzburg Univ Inst Chem & Biochem A-5020 Salzburg Austria

Eighteen plant protectant compounds were separated and determined by cyclodextrin-modified micellar electrokinetic chromatography (MEKC) in a multiclass/multiresidue method. The pesticides included are those dispersed in the greatest amounts today over agricultural acreage, and they represent 8 different classes of compounds (azoles, benzoic acids, chloroacetanilides, phenoxy acids, phenylureas, sulfonylureas, thiocarbamates, and triazines) covering a wide range of chemical reactivities and physicochemical properties. A 500 mt sample of tap water is preconcentrated by solid-phase extraction (SPE) with 300 mg combined polystyrene-divinylbenzene and methacrylate macroporous resins. Trapped analytes are eluted collectively with diethyl ether. Concentration and solvent change yield 250 mu L of an acetone "concentrate," which is further worked up and concentrated 1:10 to produce the MEKC injection solution containing 10 mmol/L sodium dodecyl sulfate (SDS) surfactant, For MEKC, 2 phosphate/SDS buffer systems were designed, each allowing complete separation of all pesticides in a single run. Sensitivity was enhanced by a self-etched bubble cell and an injection procedure which employs stacking at reversed polarity. The ability of MEKC to determine plant protectants in raw and drinking waters at the 0.1 mu g/L level, as demanded by the guidelines of the European Union, was demonstrated with spiked tap waters. Recoveries were between 75 and 110%, and limits of quantification, evaluated as method detection limits according to guidelines of the U.S. Environmental Protection Agency, ranged between 0.03 and 0.10 mu g/L. The precisions of the relative migration times were all below 0.5%.

关键词：醋酸缓冲剂色谱法胶束电动毛细管/方法环糊精类氢离子浓度农药残留量/分析质量控制水/化学

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