A forensic market survey of Indonesian lipsticks using ATR-FTIR and chemometrics

Indonesia's beauty industry has grown rapidly in recent times. One of the most popular beauty products produced and sold is lipstick. Lipstick has gained interest as a form of trace/exchange evidence due to its transferable properties since it can be transferred to surfaces such as drinking cups, clothes, cigarette butts, and straws. This is beneficial for establishing links between individuals, environments, and potential items involved in a criminal investigation. To date however, there has been no published research regarding the forensic characterisation of lipsticks available on the Indonesian market. In this study, 99 lipsticks sold on the Indonesian market were examined and differentiated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy coupled with chemometrics. Principal component analysis (PCA) and linear discriminant analysis (LDA) resulted in a model with 86.5% accuracy for distinguishing individual lipstick products. This model was then validated using a separate sample set, producing an identification accuracy exceeding 60%. This demonstrates the potential to gather investigative information from an unknown sample, even without any reference sample, in the Indonesian context.