Electrochromatographic evaluation of a silica monolith capillary column for separation of basic pharmaceuticals

A silica-based monolithic capillary column was prepared via a sol-gel process. The continuous skeleton and large through-pore structure were characterized by scanning electron microscopy (SEM). The native silica monolith has been successfully employed in the electrochromatographic separation of beta-blockers and alkaloids extracted from traditional Chinese medicines (TCMs). Column efficiencies greater than 250000 plates/m for capillary electrochromatography (CEC) separation of basic compounds were obtained. It was observed that retention of basic pharmaceuticals on the silica monolith was mainly contributed by a cation-exchange mechanism. Other retention mechanisms including reversed-phase and normal-phase mechanisms and electrophoresis of basic compounds also played a role in separation. A comparison of the differences between CEC and capillary zone electrophoresis (CZE) separation was also discussed.

Application of capillary zone electrophoresis in the separation and determination of the curcuminoids in urine

The major components of the plant curcuma longa are the curcuminoids that include curcumin, demethoxycurcumin and bisdemethoxycurcumin. It has been reported the curcuminoids have some important activities. A new CZE method with diode array detection has been developed for the separation and determination of the curcumin, demethoxycurcumin and bisdemethoxycurcumin. Three curcuminoids could be readily separated within 7 min with a 15 mM sodium tetraborate buffer containing 10% methanol (v/v) at pH 10.8, 25 kV and 30 degrees C. The method has been validated and shows good performance with respect to selectivity, reproducibility, linearity, limits of detection and recovery. The proposed method was successfully applied to determine the curcuminoids in urine. (c) 2004 Elsevier B.V. All rights reserved.

Rapid identification of pathogenic bacteria by capillary electrophoretic analysis of rRNA genes

Molecular diagnosis is playing an increasingly important role in the rapid detection and identification of pathogenic organisms in clinical samples. The genetic variation of ribosomal genes in bacteria offers an alternative to culturing for the detection and identification of these organisms. Here 16S rRNA and 16S-23S rRNA spacer region genes were chosen as the amplified targets for single-strand conformation polymorphism (SSCP) and restriction fragment length polymorphism (RFLP) capillary electrophoresis analysis and bacterial identification. The multiple fluorescence based SSCP method for the 16S rRNA gene and the RFLP method for the 16S-23S rRNA spacer region gene were developed and applied to the identification of pathogenic bacteria in clinical samples, in which home-made short-chained linear polyacrylamide (LPA) was used as a sieving matrix; a higher sieving capability and shorter analysis time were achieved than with a commercial sieving matrix because of the simplified template preparation procedure. A set of 270 pathogenic bacteria representing 34 species in 14 genera were analyzed, and a total of 34 unique SSCP patterns representing 34 different pathogenic bacterial species were determined. Based on the use of machine code to represent peak patterns developed in this paper, the identification of bacterial species becomes much easier.

Simultaneous light emitting diode-induced fluorescence and contactless conductivity detection for capillary electrophoresis

A combined detection system of simultaneous contactless conductometric and fluorescent detection for capillary electrophoresis (CE) has been designed and evaluated. The two processes share a common detection cell. A blue light-emitting diode (LED) was used as the excitation source and an optical fiber was used to collect the emitting fluorescence for fluorescent detection (FD). Inorganic ions, fluorescein isothiocyanate (FITC)-labeled amino acids and small molecule peptides were separated and detected by the combined detector, and the detection limits (LODs) of sub-μ M level were achieved.

Physicochemical characterization of the Strychnos alkaloids by capillary zone electrophoresis

A capillary zone electrophoresis (CZE) method has been developed for investigating the physicochemical characteristics of five Strychnos alkaloids in Strychnos nux-vomica L. Firstly, the dissociation constants of the five Strychnos alkaloids were determined, based on the relation between the effective mobility of the solutes and the buffer pH. The mathematical relationship was strictly deduced from the fundamental electrophoretic theory and the dissociation equilibrium. Secondly, an equation describing the relation between the migration time of alkaloids of similar structure and their molecular weights was developed and used to predict the migration order and to calculate the electrosomotic velocity. The results predicted by the theory agreed with those from experiments.

Capillary array electrophoresis for the research of asymmetric transformation reaction of L-proline to D-proline

One asymmetric transformation reaction Of L-proline (L-Pro) to D-proline was studied by a home-made capillary array electrophoresis (CAE) for the first time. The aldehyde catalysts and the organic acid solvents for the asymmetric transformation reaction were rapidly screened and the enantiomeric excess values of the asymmetric product Of L-Pro were directly obtained from the electrophoretogram of CAE.

Determination of heavy metal ions by capillary electrophoresis with contactless conductivity detection after field-amplified sample injection

A method has been developed for determining of heavy metal ions by field-amplified sample injection capillary electrophoresis with contactless conductivity detection. The effects of the 2-N-morpholinoethanesulfonic acid/histidine (MES/His) concentration in the sample matrix, the injection time and organic additives on the enrichment factor were studied. The results showed that MES/His with a low concentration in the sample matrix, an increase of the injection time and the addition of acetonitrile improved the enrichment factor. Four heavy metal ions (Zn2+, Co2+, Cu2+ and Ni2+) were dissolved in deionized water, separated in a 10 mM MES/His running buffer at pH 4.9 and detected by contactless conductivity detection. The detection sensitivity was enhanced by about three orders of magnitude with respect to the non-stacking injection mode. The limits of detection were in the range from 5 nM (Zn2+) to 30 nM (Cu2+). The method has been used to determine heavy metal ions in tap water.

Interface of chip-based capillary electrophoresis-inductively coupled plasma-atomic emission spectrometry (CE-ICP-AES)

An interface of chip-based capillary electrophoresis (CE)-inductively coupled plasma-atomic emission spectrometry (ICP-AES) that is based on cross-flow nebulization has been developed. A polydimethylsiloxane (PDMS) CE-chip with conventional cross channel layout was used. A stainless steel tube was placed orthogonal to the exit of the CE separation channel for cross flow nebulization. A supplementary flow of buffer solution at the channel exit was used to improve nebulization efficiency. Two capillaries were inserted into the CE chip near the inlet of the separation channel for sample and buffer solution injection. Syringe pumps were used to manipulate the flow rate and flow direction of the sample, buffer, and supplementary buffer solution. Peak broadening due to the shape (bulb and tube-shaped) and size of the spray chambers was studied. The smaller tube-shaped spray chamber was used because of smaller peak broadening effect due to aerosol transport. The nebulization and transport efficiency of the CE-ICP interface was approximately 10%. Ba2+ and Mg2+ ions were eluted from the CE-chip within 30 s. Resolution of the Ba2+ and Mg2+ peaks was 0.7 using the chip-based CE-ICP-AES system.