Abstract:
Laser-induced breakdown spectroscopy (LIBS) was used for the analysis of illicit drugs in powder, tablet and crystal form. The drugs of interest in this research were methamphetamine, amphetamine and MDMA (3,4-methylenedioxymethamphetamine) seized within New Zealand. An Nd:YAG 266 nm laser was used at 12.5 mJ energy under argon atmosphere. A six channel spectrometer was connected to a charge-coupled device (CCD), with a gate delay of 0.7 µs and gate width of 1.05 ms. The laser pulse repetition rate was 10 Hz and the spot size was 50 µm. 120 pulses were collected per location and this was replicated up to three times per sample. Statistical analysis was performed using hierarchical clustering, PCA, ANOVA and pairwise comparisons. This thesis was broken down into two parts. The first was investigating the feasibility of using LIBS to determine the synthesis route of illicit drugs, based on the elemental impurities present in the samples. The elemental peaks observed showed little correlation to the elements that were expected to be present. The biggest limitation was that many of the key elements (such as iodine, phosphorus, and bromine) were not detected. Analysis of reference materials consisting predominantly of these elements was also unsuccessful. The exception was a sample manufactured using the Emde method, where barium peaks were detected with high intensity. LIBS was determined to be unsuitable for determining the synthesis route of illicit drugs based on their elemental profiles. The second aspect focused on the profiling of illicit methamphetamine and MDMA samples, using LIBS. Profiling was based on the elemental peaks present in the samples and their relative intensities. The main elements detected were barium, calcium, magnesium, potassium and sodium. Precision of the method was poor, likely due to the micro-heterogeneity in the samples and variations in the ablation process, yielding RSD values in excess of 100%. The samples could not be consistently distinguished from one another, with the exception of three samples. LIBS was, therefore, concluded to be inadequate for intra-batch and inter-batch profiling of 52 methamphetamine and 19 MDMA drug samples.