Abstract:
Measurement of methamphetamine in air in former clandestine laboratories is required in order to determine exposure via inhalation accurately, and to inform theoretical models estimating inhalation exposure from surface contamination. Different solid-phase micro-extraaction (SPME) fibres were evaluated for sampling of indoor air for methamphetamine in former clandestine methamphetamine laboratories. Carboxen-PDMS fibres were determined to be sufficiently sensitive for this purpose. SPME fibres were conditioned just prior to sampling, were transported to suspected former clandestine methamphetamine laboratories in airtight, inert holders and were analysed by GCMS within 24 hours of collection. SPME-GCMS of air from former clandestine methamphetamine laboratories showed the presence of a tailing peak with a retention time and fragmentation pattern matching methamphetamine. In addition to methamphetamine, several semi-volatile compounds were detected including nicotine, fatty acids, hydrocarbons and terpineols. Static sampling of air in former clandestine methamphetamine laboratories using SPME was found to be impractival due to variability and long equilibration times in stagnant air. To obviate this problem, a novel device for dynamic SPME was constructed from Silcosteel tubing coupled to an air sampling pump. This arrangement produces a laminar airflow along an SPME fibre mounted axially in the flow. Laminar airflow reduces the boundary layer adjacent to the fibre, thereby increasing analyte uptake. Preliminary results for the new dynamic sampler indicate better reproducibility of peak and a more linear relationship between peak area and sampling time than for statis sampling. These attributes will enable shorter sampling times and lower limits of quantitation.