Identification of underivatized basic drugs in urine by capillary column gas chromatography

A capillary column gas chromatographic (GC) method is described for detecting basic drugs of abuse and their metabolites in urine. One milliliter of urine, buffered with 400 microL Tris buffer (pH 9.5) containing 1.0 microgram/mL internal standard SKF 525A (proadifen hydrochloride), is extracted with 100 microL of 5% (v/v) isoamyl alcohol/hexane. The sample is vortexed for 30 sec and centrifuged for 10 min. The upper organic layer is directly injected into the GC, thus eliminating the need for an evaporation step. The GC is equipped with two DB-1701 fused silica capillary columns and nitrogen phosphorus detectors. The column oven is temperature programmed from 185 degrees to 265 degrees C at 8 degrees/min. Identification of the unknown drugs is accomplished by using retention time relative to that of a common internal standard.