Analysis of hair after contamination with blood containing cocaine and blood containing benzoylecgonine

In post-mortem work, blood is a potential source of external contamination of hair. The present study was carried out to investigate the amount of drug absorbed into hair which has been contaminated with blood containing either cocaine or BE. Solutions were prepared containing 0.05, 0.1, 0.2, 0.5 and 3.0μg/mL of either cocaine or BE in human blood. Samples of approximately 3.2g of drug-free hair were contaminated by soaking in the blood solutions for 5min. They were then removed and left at room temperature. Approximately 0.5g of hair was collected from each of the blood soaked hair samples at 6h, 1, 2, 4 and 7 days after contamination. As each hair sample was collected it was shampoo-washed to prevent further drug absorption. Hair samples were analysed in triplicate using a fully validated method described previously. EME and cocaethylene were also measured in order to find out if cocaine or BE was breaking down to these compounds. Both cocaine and BE were absorbed into hair in significant concentrations when the concentration in the blood was 0.5μg/mL or greater; cocaine was more readily absorbed than BE. Cocaine broke down to EME (<LOQ) at 0.5μg/mL and to EME (>LOQ) and BE (<LOQ) at 3.0μg/mL. When the blood concentration of cocaine was 0.5μg/mL or less, there was no evidence of it breaking down to form BE. From the samples soaked in blood containing BE, there was no evidence of the BE breaking down. The absorption of drug into hair did not increase as the contamination period increased from 6h to 7 days.