Quantitative Determination of Codeine and Its Major Metabolites in Human Hair by Gas Chromatography-Positive Ion Chemical Ionization Mass Spectrometry: A Clinical Application

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Abstract
A highly sensitive method was developed for the quantitative analysis of codeine and morphine in human hair. After addition of deuterated internal standards, hair samples were digested overnight in 1N NaOH at 37°C. Hydrolysis was performed on certain digests by addition of 1 mL 6N HCl. Digest solutions were extracted using a solid-phase procedure with Bond Flut Certify™ extraction columns. Derivatized extracts were analyzed on a Finnigan ion trap mass spectrometer (Magnum™) in the positive ion chemical ionization mode using acetone as the reagent gas, helium as the carrier gas, and a DB-5 MS (30 m × 0.25-mm i.d.) capillary column. The assay was linear to 75 ng/mg (r = 0.99) and was capable of detecting 10 pg of codeine and morphine on-column. Intra-assay precision ranged from 8 to 20%. The method was used to quantitate codeine in human hair obtained from two male volunteers with dark brown to black hair after a single oral dose of 120 mg codeine phosphate liquid. Hair samples were plucked from the scalp for 28 days and then cut at the scalp. Codeine was detectable in 1-cm long hair (containing the bulb) at 12 h following the dose and remained detectable in the hair shaft for at least 8 weeks. Codeine metabolites were not detected in the hair of these two subjects. The method is currently being used in dose-response disposition studies to quantitate codeine and its major metabolites in human subjects.

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