Determination of phenobarbital, p-hydroxyphenobarbital and phenobarbital-N-glucoside in urine by gas chromatography chemical ionization mass spectrometry.

A sensitive and efficient analytical procedure was developed to determine phenobarbital-N-glucoside, phenobarbital and p-hydroxyphenobarbital in urine. The stable-isotope labeled internal standards used in this assay were obtained in urine from a subject who ingested 15N-labeled phenobarbital.