Journal of capillary electrophoresis and microchip technology最新文献

Indigo carmine blue is a water-soluble, light-sensitive, anionic dye most widely applied in microscopic staining techniques. It is virtually nonfluorescent in its oxidized state in aqueous solution, but when reduced under alkaline conditions, it becomes fluorescent, with absorption and emission maxima at 436 and 528 nm, respectively. It is demonstrated that the fluorescent character of the reduced form of the dye can be exploited as a label for the determination of cationic proteins by capillary electrophoresis with laser-induced fluorescence detection. Model proteins trypsinogen and cytochrome c are noncovalently labeled with indigo carmine; the bound species are reduced, rendering the indigo carmine fluorescent; and capillary electrophoresis with laser-induced fluorescence detection is used for subsequent analysis. Various buffer systems and buffer additives were examined and optimized, and a suitable pH range for optimal fluorescence intensity and protein-dye interaction was established. Fluorescence quenching of the reduced dye when bound to protein was observed in all buffer systems.

A simple CE assay for the rapid determination of the in vitro metabolic stability of verapamil in human liver microsomes has been developed and validated. Verapamil was used as the prototype drug since it is extensively metabolized in human liver microsomes. The assay showed good intra- (CV < or = 10%) and interday (CV < or = 8%) reproducibility. The recovery of verapamil after incubation at 37 degrees C for 60 min with human liver microsomes was low (15 +/- 1%) and two metabolites were detected. The method is currently in use for assessing the metabolic stability of new drug candidates at an early stage of lead optimization at Cardiome Pharma Corp. (Vancouver, BC, Canada).

A molecular modeling package has been used to systematically hydrate a series of previously built peptides. The volume data derived have been used with the log-log form of the inverse square law and published electrophoretic mobilities to test for the most likely states of hydration. Starting with the bare peptides and increasing hydration, however, the strength of correlation diminishes, indicating that the average electromigrating peptide is not extensively hydrated. The shapes of the peptides are predominantly oblate ellipsoidal, but generally do not deviate significantly from spherical and progressive hydration increases this trend. Thus, shape correction does not play a significant role in the calculations.

The possibilities of using germanate as a background electrolyte (BGE) in capillary zone electrophoresis (CZE) were investigated. Germanate can be obtained with spectral purity and, due to its two pKa values, possesses higher buffer capacity and can be used in a wider pH range than borate. The advantages and disadvantages of germanate among other polyanions for use as a background electrolyte for CE analysis are discussed.

Capillary electrophoresis was first employed for the determination of the hydrolysis rate constant of trisaccharide raffinose. Raffinose hydrolyzes in acidic medium at different temperatures; the hydrolysis products, including melibiose and fructose, were determined quantitatively. The concentration change in hydrolysis products over time provided useful information for calculating the hydrolysis constant of raffinose. The temperature dependence of the hydrolysis rate constant was used to calculate raffinose hydrolysis activation energy, which corresponds to the literature value.

A simple and efficient micellar capillary electrophoresis method for the analysis of cephalexin in oral suspensions is described. The analysis was carried out in a bare silica capillary with 75 microm i.d. and total length of 50 cm (28 cm to the detector) with a buffer solution containing 20 mM sodium tetraborate, 20 mM sodium dodecyl sulfate, and 0.1% laurylpolyoxiethylenic ether. The applied voltage was 15 kV. Detection was achieved by ultraviolet absorption at 210 nm. The calibration curve was linear within the concentration range from 40.0 to 120 microg/mL with a correlation coefficient of 0.9998. The percentage recovery was found to be 100.09 +/- 0.56. The method showed good selectivity and resolution of the drug impurities, and was found suitable to study cephalexin stability in pharmaceutical preparations.

Capillary electrophoresis is a powerful and versatile analytical tool due to the wide range of separation variables and separation methods possible. CE permits the combination of multiple separation mechanisms (e.g., chiral modifiers, polarity, pH) for the analysis of a large variety of compounds. The main advantage of CE (i.e., the broad range of separation variables) has thus far limited its application. This is due to the nonlinear influence and interactions of different parameters on separation quality, making it difficult to predict trends for the optimization of separation systems and hence hindering CE method development. In this paper, we present a means for rationalizing method development for CE separations using a genetic algorithm. We provide selected examples of separation enhancements achieved in the field of nucleotide and nucleotide sugar separation. An improved method for the enantioselective separation of amino acid derivatives (2-acetylamino-3-phenyl-propionic acid) will also be presented.