SENSITIVE FUSED-SILICA CAPILLARY GAS-CHROMATOGRAPHIC ASSAY USING ELECTRON-CAPTURE DETECTION FOR INDOMETHACIN IN OVINE FETAL FLUIDS

A sensitive gas chromatographic (GC) method with electron-capture dete ction (ECD) has been developed to quantitate indomethacin (IND) in pla sma, urine, amniotic, and tracheal fluids obtained from the pregnant s heep model. IND and the internal standard, alpha-methylindomethacin (a lpha-Me-IND) are extracted by a simple liquid-liquid extraction proced ure using ethyl acetate and derivatized with hyl-N-(tert.-butyldimethy lsilyl)trifluoroacetamide (MTBSTFA) at 60 degrees C for 50 min. The li mit of quantitation (LOQ) is 1 ng/ml with a C.V. <10% and signal-to-no ise ratio >10. Recoveries from all fluids were greater than 80%. Calib ration curves were linear over the range of 1-32 ng/ml with a coeffici ent of determination (r(2)) >0.999. Inter- and intra-day coefficients of variation were <10% at concentrations of 2-32 ng/ml, and <20% at th e LOQ, Applicability of the developed method is demonstrated for a pha rmacokinetic study of IND samples collected following long-term infusi on of IND in a chronically instrumented ovine fetus.