Journal of capillary electrophoresis and microchip technology最新文献

C18-sphingosine 1-phosphate (C18-SPP) is a sphingolipid with important functional and structural roles in cells. In this paper we report a new capillary electrophoresis technique that is coupled to a laser-induced fluorescence detection (CE-LIF) method to quantify the level of C18-SPP in biological samples. The method utilizes a commercial standard C17-sphingosine 1-phosphate (C17-SPP) derivatized with naphthalene-2,3-dicarboxaldehyde (NDA), a fluorogenic dye used to label primary amines. The detection limit for the C17-SPP NDA was 0.54 fmol. We quantified the C18-SPP in leukemic human cells before and after irradiation by gamma rays. We demonstrated that the amounts of this sphingolipid decreased after the irradiation. In a second part of this work, we used the technique to evaluate the ability of a novel transparent fused-silica capillary, which allows the use of fused-silica capillaries without burning a window. Solarization, homogeneity, and sensitivity were studied using this capillary. The results demonstrate that this new durable capillary can provide a sensitive and reproducible quantitation procedure for CE-LIF studies.

A simple and efficient method based on micellar electrokinetic capillary electrophoresis (MECC) with electrochemical detection for the determination of catechin, rutin, hyperin, and kaempferol in Plumula Nelumbini is described. Under optimum conditions, all analytes were well separated within 20 min at a separation voltage of 16 kV in a 60-mmol/L borate running buffer (pH 8.0) containing 20 mmol/L sodium dodecyl sulfate (SDS). The current response was linear over two orders of magnitude with detection limits (S/N = 3) ranging from 6.90 x 10(-8) g/mL to 1.30 x 10(-7) g/mL for all analytes. This work provides a useful method for the analysis of Plumula Nelumbini.

Corn has been known for its accumulation of flavones and phenolic acids. However, many parts of corn, except kernel, have not drawn much attention. In this work, a method based on capillary zone electrophoresis with electrochemical detection has been used for the separation and determination of epicatechin, rutin, ascorbic acid (Vc), kaempferol, chlorogenic acid, and quercetin in corn silk, leaf, and kernel. The distribution comparison of the ingredients among silk, leaf, and kernel is discussed. Several important factors--including running buffer acidity, separation voltage, and working electrode potential--were evaluated to acquire the optimum analysis conditions. Under the optimum conditions, the analytes could be well separated within 19 min in a 40-mmol/L borate buffer (pH 9.2). The response was linear over three orders of magnitude with detection limits (S/N = 3) ranging from 4.97 x 10(-8) to 9.75 x 10(-8) g/mL. The method has been successfully applied for the analysis of corn silk, leaf, and kernel with satisfactory results.

A review of microchip-based dielectrophoretic separations is presented. Benefits of miniaturization and applications of these devices are discussed. Device geometries employed to date are described.

There is an urgent need to analyze drugs and pharmaceuticals at nanoscale detection, both now and in the future. Capillary electrophoresis is a growing technique that is continuously developing with improved detectors, sample preparation units, and other components. This article describes the analysis of drugs and pharmaceuticals by capillary electrophoresis at nanoscale detection in various standard solutions, dosage formulations, and biological samples. Nanoscale detection analysis is discussed in terms of the advancement in the detectors and sample preparation methods. The coupling of the detectors and sample preparation units to capillary electrophoresis is also discussed. Attempts have been made to evaluate the optimization strategies of capillary electrophoresis conditions to achieve detection at the nanoscale. Applications of capillary electrophoresis for the analyses of simple and chiral mixtures of several drugs and pharmaceuticals at nanoscale detection are included.

A simple and reliable analytical procedure using capillary electrophoresis with UV absorbance detection for the direct enantiomeric resolution and quantitation of chiral fungicide metalaxyl is described. Several native cyclodextrins and modified beta-cyclodextrins were investigated as chiral additives to 50 mM sodium tetraborate buffer pH 9.3. The effect of their concentration on the resolution of metalaxyl enantiomeric forms was studied. The best results were achieved when 55 mM succynyl-beta-cyclodextrin in 50 mM sodium tetraborate buffer pH 9.3 was used. The optimized method showed satisfactory intraday repeatability as far as relative migration times and relative peak areas are concerned, with a detection limit of 0.1 mM for both enantiomers, and has been successfully applied to the analysis of a real plant protection product containing metalaxyl-M (metalaxyl R-form) as active ingredient.

This work is an overview of our use of affinity capillary electrophoresis (ACE) to estimate binding constants between D-Ala-D-Ala terminus peptides and the glycopeptides vancomycin (Van) from Streptomyces orientalis, teicoplanin (Teic) from Actinoplanes teicomyceticus, and ristocetin A (Rist) from Nocardia lurida. In these studies, modifications in the ACE technique, including partial-filling ACE (PFACE), flow-through PFACE (FTPFACE), on-column ligand derivatization ACE (OCLDACE), on-column receptor derivatization ACE (OCRDACE), multiple-step ligand injection PFACE (MSLIPFACE), and multiple-injection ACE (MIACE), are described and used to determine binding constants of peptides to antibiotics. The findings described herein demonstrate the advantages of ACE in estimating binding parameters between antibiotics and small peptides over other analytical techniques.

Capillary electrochromatography using cyclodextrins modified with dichloro-, dimethyl-, and chloromethylcarbamate groups were used for the enantiomeric separation of standard analytes. The chiral selector was chemically bonded to aminopropylsilanized silica particles, and these chiral stationary phases (CSPs), mixed with aminopropylsilanized silica (1:1 wt:wt), were packed into 100-microm-i.d. fused-silica capillaries. The effect of the type of cyclodextrin, the nature and position of the substituents on the phenyl ring, and the binding mode of cyclodextrin phenylcarbamates onto the silica gel surface on the chiral recognition were studied. Experimental parameters such as organic solvent concentration were varied in order to better understand the mechanism contributing to the chiral recognition of these CSPs. Good enantioseparations were achieved for a racemic flavanone (FLA) and trans-cyclopropanedicarboxylic acid dianilide (CAD).

The primary proteolysis of ewe's cheeses made from milk with different somatic cell counts (5CC) included three groups of study: cheeses made with milk with less than 500,000 somatic cells (SC); with milk containing 1 x 10(6) to 1.5 x 10(6) SC, the normal range for ewe's milk; and with milk containing more than 3.106 SC. These were examined by capillary eledrophoresis. Intact caseins as alpha(s1)-CN (I, II, and III), alpha(s2)-CN, and beta-CN (beta, beta1, and beta2) were identified. Some peptides resulting from casein proteolysis as gamma-CN and l-alpha(s1)-CN were also identified. The study reveals that proteolysis increased with ripening time and the extent of casein degradation depended on the content in SC, showing that residual intact casein, both alpha(s1)-CN and beta-CN, decreased as the SCC of milk increased because of their higher proteolytic enzyme levels. The proteolysis pattern indicated that several enzymes were implicated in increased proteolysis in high SCC cheeses.