Temperature-Dependent DART-MS Analysis of Sexual Lubricants to Increase Accurate Associations
The analysis of lubricant evidence is a recent development in sexual assault investigations and in the absence of any biological evidence may assist in linking an assailant to the victim or crime scene. An ambient ionization technique, high-resolution direct analysis in real-time mass spectrometry (HR-DART-MS), was employed to characterize a sample set of 33 water-based lubricants. As lubricants are complex multicomponent mixtures, this study investigated if different thermal desorption temperatures could elucidate different additives and provide additional information. A low-temperature, high-temperature, and thermal desorption/pyrolysis DART-MS protocol was used to characterize the water-based lubricant sample set. The strength of the methodologies was evaluated using positive and negative likelihood ratios that were calculated from inter- and intra-pairwise comparisons using Pearson correlation coefficients. The low-temperature DART-MS protocol afforded valuable information pertaining to volatile additives (e.g., flavors and fragrances) and provided positive likelihood ratios that would provide strong support for true positive and negatives than the high-temperature protocol when associating between individual samples and samples to their respective sub-groupings. The thermal desorption/pyrolysis DART analytical protocol provided enhanced differentiation between samples due to the precise temperature control using a thermal gradient. Moreover, the total ion spectra obtained from the thermal desorption/pyrolysis protocol, not only had high positive and negative likelihood ratios, this method also provided the most discrimination as determined by empirical cross entropy plots.
KeywordsLubricant analysis Likelihood ratios Pearson correlation HR-DART-MS
The authors would like to acknowledge Chikako Takei at BioChromato for providing the ionRocket used in this research.
This work was supported by the State of Florida (USA) and by the National Institute of Justice (USA) [Grant No. 2016-DN-BX-0001].
- 3.Smith, W.: PGC/MS for condom lubricant analysis. Anal. Chem. 76, 157A (2004)Google Scholar
- 9.Durex Stops Making Condoms With Nonoxynol-9 Due to Possible Increased Risk of HIV Transmission. Kaiser Health News (2004)Google Scholar
- 10.Nonoxynol-9 spermicidal lubricant. http://www.aidsmap.com/Nonoxynol-9-spermicidal-lubricant/page/1323016/. Accessed Dec 27, (2018)
- 11.Damme, L.V., Ramjee, G., Alary, M., Vuylsteke, B., Chandeying, V., Rees, H., Sirivongrangson, P., Mukenge-Tshibaka, L., Ettiègne-Traoré, V., Uaheowitchai, C., Abdool Karim, S.S., Mâsse, B., Perriëns, J., Laga, M.: Effectiveness of COL-1492, a nonoxynol-9 vaginal gell, on HIV-1 transmission in femal sex workers: a randomised controlled trial. Lancet. 360, 971–977 (2002)CrossRefGoogle Scholar
- 14.Pubus, D., Sell, C.: The Chemistry of Fragrances, vol. 276. Royal Society of Chemistry, London (1999)Google Scholar
- 17.Aitken, C.G.G., Lucy, D.: Evaluation of trace evidence in the form of multivariate data. Appl. Stat. 53, 109–122 (2004)Google Scholar
- 19.Corzo, R., Hoffman, T., Weis, P., Franco-Pedroso, J., Ramos, D., Almirall, J.: The use of LA-ICP-MS databases to calculate likelihood ratios for the forensic analysis of glass evidence. Talanta (2018)Google Scholar
- 24.Maric, M., Marano, J., Cody, R.B., Bridge, C.: DART-MS: a new analytical technique for forensic paint analysis. Anal. Chem. (2018)Google Scholar
- 26.van der Helm, H.J., Hische, E.A.H.: Application of Baye’s theorem to results of quantitative clinical chemical determinations. Clin. Chem. 25, 985–988 (1979)Google Scholar
- 27.Zweig, M.H., Campbell, G.: Receiver-operating characteristic plots: a fundamental evaluation tool in clinical medicine. Clin. Chem. 39, 561–577 (1993)Google Scholar