GLC determination of warfarin in human plasma

A specific and quantitative GLC method for warfarin in human plasma is described. The procedure uses papaverine as the internal standard and involves a dichloroethane extraction of the acidified specimen. The organic extract is evaporated, and the evaporated extract is dissolved in 50 microliter of chloroform. Aliquots of 2-3 microliter are injected into a gas chromatograph equipped with a flame-ionization detector. The sensitivity of the method is such that 0.3 microgram of intact warfarin can be detected in 1 ml of plasma. Statistical analyses indicate a recovery of 97.26 +/- 1.89% SD. The procedure was successfully applied to plasma drug level studies in humans.