Handheld spatially offset Raman spectroscopy for the simultaneous quantification of key quality parameters in...

Conventional titration methods used for quality control of cosmetic raw materials are time-consuming, labor-intensive, and require chemical reagents. This study developed a rapid and non-destructive approach based on handheld Spatially Offset Raman Spectroscopy (SORS) combined with chemometrics for the determination of iodine value (IV), saponification value (SV), and peroxide value (PV). A diverse dataset of 284 cosmetic raw materials, including oils, esters, butters, and waxes, was analyzed using a handheld Raman spectrometer. Optimization of the sampling strategy identified a low-density polyethylene (LDPE) support obtained from a Pasteur pipette as the most suitable configuration for SORS measurements, providing spectra comparable to those obtained by direct analysis while minimizing polymer interference and thermal effects. Raman spectra were preprocessed using asymmetric least squares (AsLS) and Savitzky-Golay derivatives and modeled using partial least squares (PLS) regression. The developed models showed coefficients of determination above 0.97 and RPD values above 3 for all evaluated parameters, demonstrating their suitability for approximate quantitative predictions. Permutation tests confirmed the statistical significance of the models, while elliptic joint confidence region analysis (EJCR) indicated the absence of systematic bias. Overall, the proposed approach provides a fast, reagent-free, and minimally invasive alternative to conventional titration methods, with strong potential for routine quality control of cosmetic raw materials.