Identification of sulphur in nail polish by pattern recognition methods combined with portable energy dispersive X-ray fluorescence spectral data

Abstract

Nowadays cosmetic preparations are commonplace consumer products and nail polish becomes the focus of body art. However the presence of some toxic components in the nail polish composition is harmful to health due to direct contact with the body or inhalation during its application. Indeed, contact dermatitis caused by the presence of toluene sulfonamide formaldehyde resin in nail polish is a recurring problem in people allergic to this component. The objectives of this study are to use discriminant methods of multivariate analysis to identify the samples containing sulfur using spectral data and to quantify inorganic elements in nail polish samples using portable energy dispersive X-ray fluorescence. The samples were analyzed without any kind of chemical preparation, and they were spread on parchment baking paper supported by specific cups. Partial least square-discriminant analysis enabled recognition of all the samples with S in the external validation set of samples. It was possible to quantify S, Ca, Ti, Fe, Cu, Zn, and Bi and their respective detection limits were, in mg kg⁻¹, 239, 7.4, 4.1, 1.4, 1.3, 0.8, and 1.9. The procedure has direct applications in forensic science and in quality assurance of raw materials as well as final products, offering fast, non-destructive, and robust analysis with the possibility of field measurements using portable equipment.