Determination of taurine in plasma by capillary zone electrophoresis following derivatisation with fluorescamine

A novel capillary zone electrophoresis method is described for the determin ation of taurine in plasma. The method is rapidly executed and is highly se lective for taurine as separation is based on the difference in ionisation of this amino acid from that of other amino acids. Following addition of ho motaurine as internal standard, plasma proteins were precipitated with acet onitrile and the supernatant was derivatised with fluorescamine in the pres ence of a berate buffer. Capillary electrophoresis (CE) separations were ca rried out in reverse polarity merle at 27.5 kV on a Beekman P/ACE MDQ CE in strument, equipped with a diode array detector (DAD) set at 266 nm. The sam ple tray was cooled to 5 degrees C and separations were carried out at 20 d egrees C. The fused-silica capillary was 50.2 cm in length (40.2 cm to dete ctor) with an internal diameter of 75 mu m. A capillary conditioning soluti on was applied daily in order to suppress the residual electroosmotic flow (EOF). The method, which was validated using feline plasma as the blank mat rix, was shown to be linear and reproducible over the concentration range 2 .5-100 mu g/mL. The coefficients of variation (CVs) of replicate analyses w ere less than 4.5% at 1 mu g/mL taurine in feline plasma and less than 3% f or 2.5 mu g/mL in human plasma. Recovery was estimated at 99.2% with a CV o f 4.85%. It has been demonstrated that quantitation in aqueous solution yie lds similar results to those obtained by interpolation on a plasma calibrat ion curve provided that subtraction for the taurine peak in unspiked plasma is carried out and that a suitable internal standard is employed.