A comprehensive ATR-FTIR spectroscopic analysis for the identification and differentiation of lip balms.Lip balm may be encountered as physical evidence in cases involving sexual assaults, homicides, and kidnappings.  Therefore, in this study, ATR-FTIR spectroscopy in conjunction with chemometric tools such as principal component analysis (PCA) and linear discriminant analysis (LDA) has been used for the objective identification and differentiation of 20 brands of lip balms. 
ATR-FTIR
The results show that the PCA-LDA training accuracy was 92.5%, whereas the validation accuracy comes out to be 83.33%.  A blind study using pristine samples was also performed which resulted in 80% PCA-LDA accuracy.  PCA-LDA prediction of samples on various substrates showed a higher chemometric prediction accuracy for nonporous substrates (glass, plastic, and steel), than for porous substrates (cotton cloth, cotton swab stick, dry tissue paper, and white paper) for samples kept in room temperature and under sunlight for 15 days. 
PCA-LDA