The Reaction of Methamphetamine with Nitrous Acid Gas

Abstract

Surface contamination of methamphetamine in dwellings arising from illegal manufacture and heavy abuse are a public health concern in New Zealand. Despite methamphetamine-associated health concerns, the fate of methamphetamine indoors is largely unknown. Research on nicotine reactions with ambient nitrous acid on indoor surfaces has shown that persistent carcinogenic tobacco-specific nitrosamines form, providing a source of potential health hazards in nicotine contaminated dwellings through dermal, ingestion and inhalation routes of exposure. This study aimed to address the fate of methamphetamine indoors when exposed to nitrous acid. More specifically, the aim was to establish if methamphetamine can undergo a similar surface-mediated substitution reaction in the presence of gas phase HONO within a simulated indoor environment to produce “Nnitrosomethamphetamine”. If this methamphetamine nitrosamine forms, it is a potential human carcinogen and mutagen. The surrogate isopropylbenzylamine was first used to optimise the reaction conditions required for methamphetamine to undergo nitrosation by HONO gas. The synthesis of nitrosomethamphetamine (NMA) and nitroso-isopropylbenzylamine (nitroso-IPBA) were achieved in an acidified sodium nitrite solution, providing suitable GC chromatographic and MS spectral reference data for surface nitrosation reactions by airborne HONO. A limit of detection and limit of quantification for nitrosomethamphetamine were determined for GC-MS at NMA concentrations of 0.01 μg mL-1 and 0.11 μg mL-1, respectively. The exposure of methamphetamine and the surrogate isopropylbenzylamine to gaseous HONO (3.76 ppmv ± 9%) under laboratory conditions produced their respective nitrosamines. Using different HONO exposure times of 0 min to 150 min, the yield of NMA recovered from the glass substrate ranged from 12.4 ± 1% to 20.8 ± 2%. The reaction for NMA had a second-order rate constant of 1.39 x 10-18 ± 2% cm3 mol-1 sec-1 and a significant fitted rate constant of 1.46 x 10-2 min-1. Further research is required to identify if this nitrosation reaction takes place in actual indoor settings contaminated with methamphetamine and to establish the health impacts of nitrosomethamphetamine exposure in such contaminated dwellings.