Rapid Toxicological Screening of Barbiturates in Plasma by Wide-Bore Capillary Gas Chromatography and Nitrogen-Phosphorus Detection

A rapid screening technique for the identification and quantitation of some barbiturates in plasma is reported. The method employs a one-step extraction at pH 5.8 into an organic phase, separation of compounds by gas chromatography with a wide-bore (0.75-mm i.d.) fused-silica capillary column connected to a direct injection kit, and nitrogen-phosphorus detection. Identification of each barbiturate is by retention time relative to brallobarbital, confirmed using another wide-bore column of slightly different polarity, connected to a flame-ionization detector. Rapid quantitation may be obtained with extracted standards used for drug screening. Detection threshold (0.5 micrograms/mL in a 0.5-mL serum sample and 0.5-microL injection volume), precision (CV < or = 11%), and linearity (r > 0.99) were satisfactory for routine toxicological applications.