GC/MS confirmation of barbiturates in blood and urine

A gas chromatography-mass spectrometric method is described for the quantitative measurement of 6 commonly used barbiturates in blood and urine specimens. The targeted harbiturates are butalbital, amobarbital, pentobarbital, secobarbital, mephobarbital and phenobarbital. They are recovered along with the internal standard, tolybarb, from blood and urine using liquid extraction then alkalated to form the N-ethyl derivatives. The ethylated barbiturates have symmetrical peaks which are well separated from each other on a non-polar methylsilicone capillary column. The derivatives facilitate quantitations between 50 and 10,000 ng/mL. The day-to-day CVs for all 6 barbiturates were between 4 and 9% at 200 and 5000 ng/mL. The method has been extended for identifying other acidic drugs and drug metabolites. They are mainly non-steroidal anti-inflammatory drugs, diuretics, and anticonvulsants. An additional 83 compounds can be qualitatively identified.