Detection of alprazolam in hair by negative ion chemical ionization mass spectrometry

Abstract

A sensitive and specific method for the quantitative determination of alprazolam (AL) in hair has been developed. After the addition of deuterium labeled triazolam as an internal standard, hair samples (20 mg) were digested with 1 N NaOH at 40 °C overnight. Calibrators containing known concentrations of AL dried onto drug-free hair were also prepared and digested. After digestion, the solution was cooled, adjusted to pH 9 with 6 N HC1 and 1 ml of saturated sodium borate buffer was added. The digested solutions were extracted with toluene:methylene chloride (7:3) and the organic phase was evaporated to dryness. Extract residues were treated with BSTFA and 1% TMCS and analyzed on a Finnigan-MAT TM mass spectrometer in the negative-ion chemical ionization mode with methane as the reagent gas. Chromatographic separation was achieved on a Restek-200 TM capillary column using hydrogen as the carrier gas. The assay was capable of detecting 25 pg/mg of AL and was linear to 250 pg/mg. Intra-assay precision was 11.1% at 25 pg/mg and 5.4% at 150 pg/mg. Inter-assay precision was 11.2% at 25 pg/mg and 5.3% at 150 pg/mg. This method has been used to study the hair incorporation of AL into Long-Evans rats who received 5.0 mg/kg or 7.5 mg/kg i.p. twice a day for 5 days. Preliminary results indicate that the AL concentration in the pigmented and non-pigmented hair on day 14 ranged from 60 to 100 pg/mg.