Preparation of Thin Films for Elemental Analysis of Nail Polish by Wavelength Dispersive X-Ray Fluorescence Spectroscopy

Abstract

Determination of the elemental composition of cosmetic products for quality control and impurity analysis has traditionally been performed using plasma spectroscopic techniques that feature time-consuming, hazardous, and completely destructive sample preparation steps. Wavelength dispersive X-ray fluorescence spectroscopy (WDXRF) allows for quantitative and qualitative analysis of the elemental composition of materials for a range of elemental masses with less extensive sample preparation and higher sample throughput. WDXRF analysis requires that samples be of uniform thickness and prepared reproducibly. The analysis of products with a high organic solvent content, such as nail polish, by WDXRF has not previously been successful due to sample preparation reproducibility challenges. The goal of this investigation was to develop a method for reproducible preparation of nail polish samples using a thin film applicator. Samples were quantitatively analyzed for fluorine, sodium, magnesium, aluminum, silicon, phosphates, sulfates, chloride, potassium, calcium, titanium, vanadium, manganese, and iron to demonstrate the application of this sample preparation technique to a wide range of elemental masses. The developed preparation method was used to produce replicate thin films with a high degree of reproducibility. Further, the quantitative results obtained using WDXRF exhibit strong agreement with those obtained using inductively coupled plasma optical emission spectroscopy (ICP-OES), demonstrating consistency between independent analytical techniques.