Methamphetamine: Airborne analysis and oxidative destruction

Abstract

This thesis investigates two chemical aspects of the remediation of former clandestine methamphetamine laboratories: developing methods for detecting airborne methamphetamine with short (ca. 20 min) sampling times, and oxidation of methamphetamine as a possible decontamination method. Dynamic solid phase microextraction (SPME) had been previously used to detect μg m-3 concentrations of airborne methamphetamine at former clandestine laboratories, where surface methamphetamine concentrations exceeded 60 μg/100 cm2. The current study found that for sampling times under 20 min, relative humidity values up to 70% did not influence the sorption of methamphetamine for dynamic SPME sampling. A comparison of the sorption abilities of polydimethylsiloxane (PDMS) and carboxen/divinylbenzene/polydimethylsiloxane (CAR/DVB/PDMS) fibres revealed that the PDMS fibre was twice as effective at sampling methamphetamine, under identical conditions. Capillary microextraction (CME), a high-surface area microextraction technique that has been used for sampling volatile organic compounds, was investigated as a more sensitive alternative to dynamic SPME sampling. CME devices were used to sample methamphetamine vapour (0.42-4.2 μg m-3) and analysed using GC/MS. The CME-GC/MS technique was found to be over 30 times more sensitive than the original dynamic SPME-GC/MS method. The CME devices were not affected by changes in relative humidity, and could be stored for up to 3 days post-sampling, without any loss of analyte. We demonstrated that on-sorbent derivatisation of methamphetamine with pentafluorobenzyl chloroformate could be conducted using the CME devices, improving both the intra-device variability and the detection limit of the analysis. Finally, four peroxide-based oxidations of methamphetamine were examined as potential methods for decontamination, and the reaction products were identified. 10% hydrogen peroxide, in the presence of an Fe-TAML catalyst, was the most effective, decomposing >99% of the methamphetamine into products including ii phenyl-2-propanone and benzaldehyde. BioOxygenÒ Chem-Decon, a commercial proprietary formulation, was effective in the removal of 93% of the methamphetamine, with the major identified product being phenylacetone oxime. 10% hydrogen peroxide, and 15% alkalised hydrogen peroxide were less effective under the conditions used, oxidising less than half the methamphetamine into products that could not be identified using our GC/MS and LC/MS protocols.