The forensic analysis of lubricant evidence is another tool that can be used in sexual assault investigations, especially in the absence of any biological evidence. However, many lubricants cannot be analyzed via traditional methods, such as gas chromatography-mass spectrometry, because many lubricants are silicone based. Therefore, Fourier transform infrared spectroscopy is traditionally used to identify the primary lubricant base; however, signals from minor components present in the sample, that can be used to differentiate lubricants, cannot be easily isolated to aid in differentiation or association of lubricants. Using high resolution direct analysis in real time - time-of-flight mass spectrometry (DART-TOFMS) can identify the lubricant base as well as minor components. This project aims to highlight how different ionization temperatures can be used to enhance or minimize minor components to aid in the analysis of lubricants. In this study, multicomponent water-based lubricants were analyzed via DART-TOFMS. Samples with and without additives, i.e. flavors, fragrances, etc., were selected to evaluate which ionization temperature elucidated the additives and this increased association/differentiation capabilities. Samples were analyzed at 150oC and 350oC using DART-TOFMS. Samples were also analyzed using a thermal gradient attachment for the DART-TOFMS, which analyzes samples from 50oC to 600oC in 7 minutes. The thermal attachment also provided individual component profile data during the analysis that could be used to provide better association values using Pearson correlation coefficients. Pearson coefficients were used to calculate the similarity of each pair-wise comparison and to develop the receiver operator curves. Likelihood ratios were calculated for each temperature sample set to determine which temperature profile provided higher likelihoods of accurately associating samples from the sample manufacturer or class. It was determined that low temperatures increased accurate sourcing for flavored/fragranced lubricants versus the high temperature. The thermal gradient method provided benefits of both the low and high temperatures.

Temperature Controlled Ambient Ionization of Lubricants for Increased Match Determination

2019 Spring National Meeting

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