Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta A chemometric strategy for forensic analysis of condom residues: Identificationandmarkerprofilingofcondombrandsfromdirectanalysisin real time-high resolution mass spectrometric chemical signatures Allix M. Coon, Samira Beyramysoltan, Rabi A. Musah ⁎ Department of Chemistry, State University of New York at Albany, 1400 Washington Ave, Albany, NY 12222, United States ARTICLEINFO Keywords: Sexual assault Condom brand Lubricant Direct analysis in real time mass spectrometry Brand Chemometrics Conformal prediction ABSTRACT The rapid and accurate identification of condom-derived lubricant traces takes on heightened importance in sexualassaultcaseswheretheassailanthasusedacondominordertoavoidleavingbehindincriminatingDNA evidence.Previousreportshavedemonstratedthatavarietyoftechniquescanbeusedtoconfirmthatagiven residue is condom-derived, based on the detection of spermicides, slip agents and/or other common additives. However, limited success has been achieved in differentiating brands from among a broad range of condom types. In this study, the utility of direct analysis in real time-high resolution mass spectrometry (DART-HRMS) combined with chemometrics, for the rapid and accurate attribution of brands to condom residues of various types, was explored and developed. A database of condom residue spectra comprised of 110 different condom types representing 16 brands was generated, with the spectra serving as representative fingerprints for each brand. The spectral fingerprints were subjected to pre-processing prior to the application of Partial Least Squares-DiscriminantAnalysis(PLS-DA)whichwasusedtogenerateaclassifierthatpermittedidentificationof condombrandswithanaccuracyof97.4%.AnadditionalcriterionwasimposedonthePLS-DAtoprovidethe confidence level and credibility of each prediction. The effect of time since deposition, the presence of con- taminants and the influence of residue transfer on the prediction accuracy of the model were also assessed. The results from Sparse Discriminant Analysis (SDA) and PLS-DA were followed by application of the Student's t-testtodetermine m/z valuesrepresentativeofsmall-moleculemarkersthatweremostimportantfor defining brand classes. The m/z values revealed by the two methods were found to be consistent in indicating which masses were representative of markers. The SDA method also provided low-dimensional views of the discriminative directions for classification of condom residues, thereby enabling easy visualization of the re- lationship between the indicated m/z valuesandbranddiscrimination.Theresultsfurtherrevealedasubsetof 14 m/z valuesthatwereobservedinall110condomsrepresentingthe16brands,andsomeofthesemayserveas potentialuniversalsmall-moleculecondommarkers.Overall,theresultsshowthattheDART-HRMSdatabaseof condomresiduespectracanbeusedtoidentifyresiduesbasedondifferencesinchemicalcomponentspeculiarto each brand. The database can be readily expanded to include more condoms. 1. Introduction The ability to identify condom-derived trace evidence is gaining in importance because of the increasing frequency with which perpe- tratorsofsexualassaultusecondomsinordertoavoidleavingbehind incriminating DNA evidence. When DNA is absent because a condom was used, the condom-derived lubricant traces left behind may have significant evidentiary value. In such cases, it would be highly bene- ficial to be able to not only confirm the presence of the lubricant, but perhaps even identify the brand of condom used. Blackledge and Vincenti reported two cases in which condom traces provided im- portantassociativeevidence.Inbothinstances,confirmationoftheuse of a condom was based on detection of the silicone-based lubricant polydimethylsiloxane (PDMS) by FT-IR and desorption chemical https://doi.org/10.1016/j.talanta.2018.09.101 Received 16 July 2018; Received in revised form 25 September 2018; Accepted 27 September 2018 Abbreviations: DCI, desorption chemical ionization; DNA, deoxyribonucleic acid; FT-IR, Fourier Transform Infrared Spectroscopy; GC-MS, Gas Chromatography MassSpectrometry;MALDI-MS,MatrixAssistedLaserDesorptionIonizationMassSpectrometry;LC-MS,LiquidChromatographyMassSpectrometry;DRIFTS,Diffuse Reflectance Infrared Fourier Transform Spectroscopy; NMR, Nuclear Magnetic Resonance ⁎ Corresponding author. E-mail address: rmusah@albany.edu (R.A. Musah). Talanta 194 (2019) 563–575 Available online 27 September 2018 0039-9140/ © 2018 Elsevier B.V. All rights reserved. T