title: Analysis of sexual assault evidence: statistical classification of condoms by ambient mass spectrometry.
abstract: Desorption electrospray ionization mass spectrometry (DESI-MS) and easy ambient sonic-spray ionization mass spectrometry (EASI-MS) are employed here in the forensic analysis of chemical compounds found in condoms and relative traces, and their analytical performances are compared. Statistical analysis of data obtained from mass spectra only was applied in order to obtain classification rules for distinguishing ten types of condoms. In particular, two supervised chemometric techniques [linear discriminant analysis (LDA) and soft independent modeling of class analogy (SIMCA)] were carried out on absolute and relative intensity values to test the performances of statistical models in terms of predictive capacity. The achieved classification of samples was excellent because of the high prediction percentages of the method used both for DESI and EASI mass spectrometry analyses, confirming these two as potential ambient ionization techniques for forensic analyses in case of sexual assault crimes. EASI-MS showed 99% prediction ability for LDA using relative data and 100% prediction ability for SIMCA using both absolute and relative ones, while DESI showed 94% prediction ability for both LDA and SIMCA. The absence of any sample preparation technique gives advantages in terms of sample preservation and reduced contamination, allowing successive analyses to be performed on the same sample by other techniques.
authors.affiliation: Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Cubo 12/C, I-87036, Arcavacata di Rende, Cosenza, Italy.
authors.forename: Mario F
authors.initials: MF
authors.lastname: Mirabelli
authors.affiliation: Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, Canada.
authors.forename: Demian R
authors.initials: DR
authors.lastname: Ifa
authors.affiliation: Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Cubo 12/C, I-87036, Arcavacata di Rende, Cosenza, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Sindona
authors.affiliation: Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Cubo 12/C, I-87036, Arcavacata di Rende, Cosenza, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Tagarelli
mesh_terms: D017280:Condoms; D016002:Discriminant Analysis; D005554:Forensic Medicine / Q000379:methods*; D006801:Humans; D054327:Lubricants / Q000032:analysis / Q000737:chemistry; D015233:Models, Statistical; D011108:Polymers / Q000032:analysis / Q000737:chemistry; D012742:Sex Offenses; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013089:Spermatocidal Agents / Q000032:analysis / Q000737:chemistry
chemical_list: D054327:Lubricants; D011108:Polymers; D013089:Spermatocidal Agents
keywords: ambient ionization; condoms; forensics; sexual assault crimes; statistical classification