GC and GC-mass spectrometric determination of p-hydroxyphenobarbital extracted from plasma, urine, and hepatic microsomes.

Analytical methodology was developed for the quantitation of p-hydroxyphenobarbital extracted from plasma, urine, and hepatic microsomes. p-Hydroxyphenobarbital was derivatized with an appropriate n-alkyl iodide in the presence of a methanolic base in aprotic solvent medium. The peralkylated derivatives were stable indefinitely and were quantitated by the sensitive and selective method of GC nitrogen-selective detection and/or selected ion monitoring. The accuracy, precision, and cross verification of all methods were good. The analysis was subsequently used to study the effects of other drugs on phenobarbital biodisposition.