Testing of the anabolic stanozolol in human hair by gas chromatography-negative ion chemical ionization mass spectrometry

Abstract

A sensitive, specific and reproducible method for the quantitative determination of stanozolol in human hair has been developed. The sample preparation involved a decontamination step of the hair with methylene chloride and the sonication in methanol of 100 mg of powdered hair for 2 h. After elimination of the solvent, the hair sample was solubilized in 1 ml 1 M NaOH, 15 min at 95 degrees C, in the presence of 10 ng stanozolol-d3 used as internal standard. The homogenate was neutralized and extracted using consecutively a solid-phase (Isolute C18) and a liquid-liquid (pentane) extraction. After evaporation of the final organic phase, the dry extract was derivatized using 40 microl MBHFA-TMSI (1000:20, v/v), incubated for 5 min at 80 degrees C, followed by 10 microl of MBHFBA, incubated for 30 min at 80 degrees C. The derivatized extract was analyzed by a Hewlett-Packard GC-MS system with a 5989 B Engine operating in the negative chemical ionization mode of detection. Linearity of the detector response was observed for stanozolol concentrations ranging from 5 to 200 pg/mg with a correlation coefficient of 0.998. The assay was capable of detecting 2 pg of stanozolol per mg of hair when approximately 100 mg hair material was processed, with a quantification limit set at 5 pg/mg. Intra-day precision was 5.9% at 50 pg/mg and 7.8% at 25 pg/mg with extraction recoveries of 79.8 and 75.1%, respectively. The analysis of a 3-cm long hair strand, obtained from a young bodybuilder (27 year old) assuming to be a regular user of Winstrol (stanozolol, 2 mg), revealed the presence of stanozolol at the concentration of 15 pg/mg.