Microfurnace or filament pyrolyzer: an example of pyrolysis-GC/MS for condom lubricant analysis

Abstract

Condom lubricants have been shown to contain polydimethylsiloxane (PDMS) in over 95% of cases, but PDMS is difficult to analyze using standard GC–MS or LC-MS due to their size, apolarity and issues with solvents and plasticizers. Py-GC–MS was established as one of the more relevant analytical techniques for PDMS evidence analysis. However, different pyrolysis units and various GC columns are available for use Py-GC–MS. These two parameters are likely to significantly affect the repeatability, reproducibility and sensitivity of the analysis and, as such, affect the recovery of condom traces in casework. This work employed a resistively heated filament pyrolyzer and an isothermal oven pyrolyzer to investigate differences in the profiles generated by the pyrolysis units in the analysis of 4 condom lubricants. Similar experiments were performed using different columns, with the same pyrolyzers, to determine which gave optimal compound separation. This enabled assessment of the combinations in terms of the qualitative and semi-quantitative repeatability, allowing recommendations for optimized condom residue analysis. Results indicate that the use of a HP-5MS column, coupled to an isothermal oven pyrolyzer, is the optimal instrument configuration for condom residue analysis, based on repeatability, reproducibility and sensitivity of PDMS analysis.