Thiamine analysis in biological media by capillary zone electrophoresis with a high-sensitivity cell

A capillary zone electrophoresis method with high-sensitivity cell (Z-cell) has been developed for the determination of thiamine in biological media (plasma, urine, saliva). The urine samples were diluted (1:1, v/v) in water and were directly injected into the apparatus. For the quantitative assay of thiamine in plasma it is necessary to precipitate the protein component. Good results were achieved by treating the sample with acetonitrile (1:3, v/v). Using a capillary with high sensitivity cell led to an approximately nine-fold improvement of the detection limit compared to standard capillaries and four-fold improvement compared to capillary with bubble cell. The samples in the biological media were analysed using a calibration curve for thiamine concentrations between 0.1 and 200 microg ml(-1). The detection limit, the effective mobility and the relative standard deviation of the migration times and of the peak areas were determined.