Rapid determination of drugs in biofluids by capillary electrophoresis Measurement of antipyrine in saliva for pharmacokinetic studies

A micellar electrokinetic capillary chromatography method was developed that permitted the resolution of antipyrine from endogenous compounds and its quantitation in neat saliva in as little as 1 min. Final conditions were: SpectraPhoresis 1000, 30(23) cm × 50 μm silica capillary, 50 mM sodium phosphate pH 9.6, 50 mM SDS, 10 s hydrodynamic load, detection scanning 200–300 nm or 260 nm, run 25 kV. To overcome the effects of Joule heating the capillary was cooled to 15°C. Sensitivity was <10 μM and linearity extended to 350 μM. Comparison with an HPLC assay demonstrated that hydrodynamic injection gave a loading bias unless samples and standards were of equal viscosity. For 75 samples from five subjects the correlation of CE vs. HPLC was then r = 0.99.