SIMULTANEOUS ANALYSIS OF FLUNIXIN, NAPROXEN, ETHACRYNIC-ACID, INDOMETHACIN, PHENYLBUTAZONE, MEFENAMIC-ACID AND THIOSALICYLIC ACID IN PLASMA AND URINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Simple and reproducible high-performance liquid chromatographic (HPLC) and gas chromatographic-mass spectrometric (GC-MS) methods have been developed for the simultaneous analysis of several acidic drugs in horse plasma and urine. Although the capillary GC-MS column provided better separation of the drugs than the reversed-phase C8 (3-mu-m, 75 mm) HPLC column, the total analysis time with HPLC was shorter than the total analysis time with GC-MS. The HPLC system equipped with a diode-array detector provided simultaneous screening (limit of detection 100-500 ng/ml) and confirmation (limit 1.0-mu-g/ml) of the drugs. The HPLC system equipped with fixed-wavelength ultraviolet and fluorescence detectors provided a relatively sensitive screening [limit of detection 50-150 ng/ml for ultraviolet and 10 ng/ml for fluorescence (naproxen only) detectors] of the drugs. However, the positive samples had to be confirmed by using either the diode-array detector or the GC-MS system. The GC-MS system provided simultaneous screening and confirmation of the drugs at very low concentrations (20-50 ng/ml).