Determination of rubidium, sodium, calcium and thiamine in a pharmaceutical preparation by capillary isotachophoresis

Spectrophotometric determination of vitamin B1 in a pharmaceutical formulation using triphenylmethane acid dyes

A highly sensitive colour reaction has been developed, based on the fact that vitamin B(1) reacted with a triphenylmethane acid dye such as thymol blue, bromothymol blue, bromophenol blue, bromocresol green, phenol red or cresol red to form an ion-association complex in a weak-base aqueous solution in the presence of some solubilization agents e.g. polyvinyl alcohol, emulgent OP, Triton X-100 or Tween-20. The wavelengths of maximum absorbance of the six ion-association complexes were between 420 and 450 nm, and fading reaction appeared at the longer wavelength and the maximum fading wavelengths were between 550 and 620 nm. The reactions had highly sensitivities and their apparent molar absorptivities of the colour reactions were (0.82-1.65) x 10(5) l mol(-1) cm(-1) and those of fading reactions were (1.26-3.92) x 10(5) l mol(-1) cm(-1) depending on the different dye systems. The composition ratio of the ion-association complex was vitamin B(1):dye = 1:1 as established by Job's and equilibrium shift methods. The method had good selectivity and could be applied to direct spectrophotometric determination of vitamin B(1) in aqueous phase without using organic solvent extraction. Therefore, the method was simple and rapid. The colour reaction mechanism was discussed with the quantum chemistry method.

Applications of capillary electrophoresis in pharmaceutical analysis

The role of capillary electrophoresis (CE) in the analysis of peptide/proteins, chiral pharmaceuticals, and other small-molecule drugs has been reviewed. Potential uses of CE range from purity and structural confirmation to a micropreparative technique. Strategies for the prevention of protein wall adsorption include the use of extreme pH values, surface-modified capillaries, and high ionic strengths employing salts of alkali metals or by the addition of zwitterionic surfactants to the background electrolyte. Chiral separations of amino acids and other racemic pharmaceuticals have been achieved by micellar electrokinetic chromatography or by the introduction of cyclodextrins/modified cyclodextrins or other reagents to the running buffer. Applications of capillary electrophoresis to the analysis of small-molecule pharmaceuticals include determinations of drugs and/or excipients in various pharmaceutical preparations and the analysis of miscellaneous pharmaceuticals in standard solutions and biological fluids. The complementary nature of capillary electrophoresis and HPLC, in addition to future expectations of CE in pharmaceutical analysis, is discussed.