Stability of Cannabinoids in Hair Samples Exposed to Sunlight

Abstract

It has been well recognized that hashish and marihuana lose potency during storage because of a decrease in the content of tetrahydrocannabinol (THC), which is the major psychoactive constituent of cannabis (1). The effect of oxygen on stored plant and resin materials or solutions of pure cannabinoids seems much less significant than that of higher temperatures (≥37 °C) or light (2)(3)(4)(5)(6)(7). A few data are available on the stability of THC and major metabolites in blood (8)(9)(10)(11). However, the stability of cannabinoids in the hair shaft has not been addressed, although scalp hair represents one of the most exposed parts of the body. Therefore, a study was performed to elucidate whether cannabinoids such as THC, cannabinol (CBN), or cannabidiol (CBD), which usually are determined from hair samples, would exhibit similar instability in this particular biological matrix when exposed to solar radiation. Clipped hair bundles (n = 11) suggested to be cannabis positive were washed twice with dichloromethane (10 mL each time for 10 min) and divided into four strands each. Two of the strands were kept in the dark at ambient temperature. Under these storage conditions, the analytes and their concentration remained unchanged as ascertained in a preliminary experiment (data not shown). The other two strands were stored outside in quartz glass vials (Pyrex) and exposed to natural …