Department of Forensic Medicine & Science, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
* Edinburgh Drug Addiction Study, 1 Muirhouse Avenue, Edinburgh EH4 4PL, Scotland, UK, & Department of General Practice, University of Edinburgh, Edinburgh EH8 9YL, Scotland, UK

Methods for the surface decontamination and extraction of the specimens were evaluated. The nail clippings were decontaminated by sonication in 0.1% sodium, dodecyl sulfate (SDS) followed by sonication in distilled water and methanol. Whereas the SDS and water washes were discarded, the methanolic washes were analysed for the presence of analytes. The nail clippings were then hydrolysed in 1 M NaOH and the hydrolysates were extracted with organic solvents prior to instrumental analysis. Extracts were analysed by RIA, GC-MS or GC equipped with ECD.

Positive RIA results were obtained with specimens from 6 known drug users. The average cannabinoid concentration in fingernail clippings determined by RIA was 1.03 ng/mg. Using GC-MS, the mean D⁹-tetrahydrocannabinol concentration in fingernail clippings from a further 14 known cannabis users was 1.44 ng/mg. Finally nail clippings from another 6 known drug users were analysed for diazepam and its mean concentration was found to be 25.71 ng/mg. The limits of detection for the RIA method for cannabinoids and the GC-MS method for D⁹- tetrahydrocannabinol were determined to be better than 0.1 ng/mg. The limit of detection of the GC-ECD method for diazepam was lower than 0.001 ng/mg. The extraction recoveries for our methods were better than 81%.

Based on these results, fingernails appear to be potentially useful biological specimens for the detection of past drug use in cases of medico-legal interest.