Effective and reproducible capillary electrophoretic separation of thiols under conditions where exceptionally high current is generated

Development and validation of a capillary electrophoresis method for ximelagatran assay and related substance determination in drug substance and tablets

The advantages of simplicity, selectivity, versatility and ease of use of free solution capillary electrophoresis (CE) present an orthogonal and complementary separation technique to the established methods of liquid chromatography (LC) for pharmaceutical analysis. This work presents the development and performance of a suitable CE method for ximelagatran (formerly H 376/95) assay and related substance determination in both drug substance and tablets. The method employed was a low pH phosphate buffer, to which acetonitrile and hydroxypropyl-beta-cyclodextrin were added, in order to facilitate the separation of ximelagatran and its related substances. An applied field of 350 V/cm was used and all compounds were resolved in approximately 20 min. Benzamidine hydrochloride was used as an internal standard in quantification. The data indicate that the performance of the validated method offers equivalent and complementary information, in terms of selectivity, sensitivity, accuracy, linearity and precision, to that of an established gradient LC method employed for similar purposes. Robustness of the method was investigated by experimental design and evaluated using multivariate calculations.

A method for UV-bonding in the fabrication of glass electrophoretic microchips

This paper presents an approach for the development of methodologies amenable to simple and inexpensive microchip fabrication, potentially applicable to dissimilar materials bonding and chip integration. The method involves a UV-curable glue that can be used for glass microchip fabrication bonding at room temperature. This involves nothing more than fabrication of glue "guide channels" into the microchip architecture that upon exposure to the appropriate UV light source, bonds the etched plate and cover plate together. The microchip performance was verified by capillary zone electrophoresis (CZE) of small fluorescent molecules with no microchannel surface modification carried out, as well as with a DNA fragment separation following surface modification. The performance of these UV-bonded electrophoretic microchips indicates that this method may provide an alternative to high temperature bonding.

Nitrite and nitrate measurement in human urine by capillary electrophoresis

Nitrite and nitrate have been widely used as markers for nitric oxide (NO) formation in vivo and represent the major NO oxidation products in biological fluids. In the present study, the use of capillary electrophoresis (CE) in the measurement of nitrite and nitrate in human urine is described. Urine samples were electrophoresed in an extended light path fused-silica capillary (104 cm; 75 microm ID) at an applied negative potential of 30 kV, and UV detection at 214 nm. Using electrokinetic sample injection (-6 kV x 20 s), we found that urine concentration, pH, sodium and chloride interfered with nitrite and nitrate detection. The detection of nitrite and nitrate was decreased when hydrodynamic sample injection was used (30 mbar x 60 s). However, basal levels of urinary nitrite (0.25 +/- 0.05 microM) and nitrate (591 +/- 115 microM) were detected and no interference by variations in urine concentration and pH was noted when hydrodynamic sample injection was used. Thus, hydrodynamic sample injection is convenient for the measurement of urinary nitrite and nitrate and avoids the effect of variations in urine matrices and pH on nitrite and nitrate detection.