Use of gas chromatography/mass spectrometry with positive chemical ionization for the determination of opiates in human oral fluid.

An analytical method for the simultaneous determination of codeine, morphine and 6-acetylmorphine (6AM) in human oral fluid was developed. The method involves liquid-liquid extraction in Toxitubes A, derivatization with 99:1 (v/v) N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)/trimethylchlorosilane (TMCS), and gas chromatography/mass spectrometry with positive chemical ionization (GC/PCI-MS) determination. The detector response was linear over the concentration range 30-500 ng/mL with coefficients of correlation higher than 0.99. The precision was acceptable with coefficients of variation less than 7.5%. The limits of detection achieved were 0.7 ng/mL for codeine, 2.0 ng/mL for morphine, and 0.6 ng/mL for 6AM. The method proposed was applied to 80 oral fluid samples from opiates users, 98% of which were positive for the three analytes. Human oral fluid is a suitable biological fluid for the determination of opiates by GC/PCI-MS.