Determination of pentobarbital in serum by electron-capture GLC

A GLC method was developed for pentobarbital in serum. After extraction from serum, a pentafluorobenzyl derivative was prepared and quantitated by electron-capture detection. The method has a sensitivity of 0.1 microng/ml of serum, and the amount detectable is less than 0.2 ng/injection. Hexethal was used as the internal standard. Derivatives of other barbiturates were also made. NMR and mass spectrometric analyses confirmed the proposed structure of the 1,3-bis(pentafluorobenzyl) derivative of pentobarbital. The procedure was successfully applied to measurement of serum pentobarbital levels in humans.