Forensic Characterization of Lipsticks Using Time-of-Flight Secondary Ion Mass Spectrometry

Abstract

Lipstick smear analysis can provide valuable information in forensic investigations, but it is difficult to distinguish lipstick products because their complex compositions can vary with the brand and product. In this study, various lipstick samples were analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). ATR-FTIR method was useful for preliminary categorization of lipstick. Generally, ToF-SIMS provides chemical information about sample surfaces. Each lipstick sample showed characteristic ion peaks in the ToF-SIMS spectra. To investigate the effect of the substrate on the ToF-SIMS spectra, two lipsticks were applied to five different substrates (white paper, glass slide, tissue paper, orange cotton fabric, and black cotton fabric) and analyzed using principal component analysis. Trace lipstick smears deposited on tissue paper and cigarette butts were analyzed and compared with results from reference lipstick samples. ToF-SIMS is a promising technique for discrimination and classification of lipsticks in forensic science.