Analysis of squalene and its transformation by-products in latent fingermarks by ultrahigh-performance liquid chromatography-high resolution accurate mass Orbitrap™ mass spectrometry

• Published in: Forensic chemistry 2020-03, Vol.17, p.100193, Article 100193
• Main Authors: Dorakumbura, Buddhika N., Busetti, Francesco, Lewis, Simon W.
• Format: Article
• Language: English
• Subjects: By-products; Degradation; Fingermark composition; High resolution accurate mass Orbitrap™ mass spectrometry; Squalene
• ISSN: 2468-1709; 2468-1709
• DOI: 10.1016/j.forc.2019.100193

[Display omitted] •Fate of squalene in latent fingermarks on non-porous surfaces investigated.•Squalene monohydroperoxide found to be short-lived.•Squalene epoxide relatively stable up to 7 days under dark and aquatic conditions.•Oxidation by-products of cholesterol exhibited a growth over time.•These show potential as biomarkers for targeted visualisation of aged deposits. Transformation of squalene and its by-products in latent fingermarks over time under different storage conditions (light, dark, and underwater) was examined through ultrahigh-performance liquid chromatography-high resolution accurate mass Orbitrap™ mass spectrometry. Complications of assessing fingermark compositional variation over time using multiple samples with varying initial compositions were elucidated and a more rational approach was successfully demonstrated. Squalene was detected in all fresh natural fingermarks deposited on non-porous surfaces and the amount ranged between 0.20 and 11.32 μg/5 fingertips. A notable difference in the transformation of squalene was observed with different storage conditions, where a dark aquatic environment accelerated degradation of squalene compared to dark but dry conditions. Squalene monohydroperoxide was extremely short-lived in natural deposits while the amount of squalene epoxide was still increasing relative to the initial amount, after ageing under dark and aquatic conditions for up to 7 days. Some oxidation by-products of cholesterol were also tentatively identified, which exhibited a growth over time against their initial concentration under any of the storage condition tested. These by-products, therefore, show potential as biomarkers for targeted visualisation of aged deposits.