Evaluation of amphetamines diffusion in hair after contact with amphetamines-containing blood

Amphetamine-type stimulants are the third most widely consumed category of illicit drugs worldwide. Faced with the growing problem of amphetamine-type stimulants, numerous qualitative and quantitative techniques have been developed to detect amphetamine (AMP), methamphetamine (MET), MDMA, MDEA or MDA in biological matrices, including hair. Hair analysis is widely used in forensic medicine, but one of its main drawbacks remains external contamination. In this study, we investigated the possibility of hair contamination through external exposure to blood containing AMP, MET MDMA, MDEA or MDA at 2 ng/mL; 20 ng/mL; 200 ng/mL or 2000 ng/mL after 6 h, 1, 3, 7 or 14 days of contact protected from light at room temperature (RT or 20 °C) or at 4 °C. Dried extracts of hair samples were analyzed by UPLC-MS/MS after extensive washings in several baths of water, methanol and acetone before grounding. At the end of our study, contamination of hair was observed from 6 h of contact with all tested amphetamine-type stimulants. The concentrations found in hair ranged from 3 ± 1 to 1464 ± 10 pg/mg, 5 ± 1 to 5070 ± 160 pg/mg, 3 ± 1 to 1269 ± 60 pg/mg, 4 ± 1 to 1860 ± 113 pg/mg and from 8 ± 1 to 1041 ± 44 pg/mg for AMP, MET, MDMA, MDEA and MDA, respectively. Possibly due to its low polar surface area, MET was the most prone to contaminate. As anticipated, hair contamination was mainly dependent on the concentration of all molecules in the contaminating blood, reaching the SOHT cut-off of 200 pg/mg when amphetamine-type stimulants are at toxic or lethal concentrations in the blood. These observations call for caution in interpreting exposure to these substances in such forensic situations.