Analysis of condom evidence commonly focusses on the detection of silicone-based lubricants, such as polydimethylsiloxane. However, water-based compounds such as propylene glycol or glycerin can also be used as condom lubricants and may, therefore, be detected as transferred traces. Evaluation of the variability amongst a large sample set from an international market is needed to determine what are the most likely compounds that may be detected in casework. In this study, 165 condoms, personal hygiene products, lubricants, creams and oils were analysed using gas-chromatography coupled to a mass spectrometer detector (GCMS). The resulting compounds were identified using mass spectral databases, then the data were extracted and evaluated using established multivariate statistical techniques, such as principal component analysis and discriminant analysis. Qualitative visual inspection, as well as statistical analysis, revealed at least twelve different groupings within the dataset. Discrimination was based on variations in the concentration of major compounds, as well as the presence or absence of minor compounds, such as anaesthetics. For the 127 condoms examined, 2 were exclusively water-based lubricated (1.5 %) and 6 contained silicone and water-based components (4.7 %). All the others were only silicone-based (119 condoms, 93.7 %). Strong variation was observed between the different sources of products. Personal hygiene products (PHP), creams, lubricating oils, personal lubricants, and condoms were found to have different chemical compositions. Hence GCMS can be used to assist in the differentiation of water-based residues for investigative purposes.
Keywords: Chemometrics; Condoms; Forensic; Glycerin; Lubricant; PCA; Propylene glycol; SVM.
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