Nail analysis for drugs of abuse: Extraction and determination of cannabis in fingernails by RIA and GC-MS

Fingernail clippings were evaluated as analytical specimens for the detection and quantitation of cannabinoids. Specimens were obtained from consenting adults attending a drug clinic, along with information concerning the drugs which they had used over the previous six months. Methods for the surface decontamination and extraction of the specimens were evaluated. Detergent, water, and methanol washes followed by alkaline hydrolysis and liquid-liquid extraction were selected for use in the study. Extracts were analyzed by radioimmunoassay (RIA) and gas chromatography-mass spectrometry (GC-MS) to detect and quantitate cannabinoids present in fingernail clippings. Positive RIA results were obtained from specimens from six known cannabis users. The mean cannabinoid concentration in fingernail clippings determined by RIA was 1.03 ng/mg. Using GC-MS, the mean Δ9- tetrahydrocannabinol concentration in fingernail clippings from a further 14 known cannabis users was 1.44 ng/mg. Using GC-MS, the average 11-nor-Δ9- tetrahydrocannabinol-9-carboxylic acid concentration in fingernail clippings from three known cannabis users extracted in acidic pH was 19.85 ng/mg. Based on these results, fingernails are potentially useful biological specimens for the detection of past cannabis use in cases of medicolegal interest.