A brief revision of the suspension-assisted direct solid analysis by TXRF spectrometry

Abstract

This brief revision compiles and reexamines the general strategy developed thus far for quantifying the elemental composition of solid materials using TXRF without employing acid chemical manipulation based on the previous suspension of the solid samples. This kind of analysis converts to the TXRF methodology in a green chemical analytical alternative with higher care for the environment and low analytical cost. The reviewed TXRF methodology is the sum of a Suspension Assisted (SA), which uses grinding, ultrasound, and surfactant addition, in conjunction with the Direct Solid Analysis (DSA), where the continuous agitation of suspension, internal standardisation and final deposition are made for the quantitative analysis by means TXRF. A general TXRF solid suspension analysis (SA/DSA-TXRF) protocol is proposed and applied to analyse a commercial sample of bentonite clay used for cosmetic applications as a typical sample example. Several critical questions related to the general process of suspension and deposition are discussed. Two crucial examples are the correct transfer of the suspended sample, which can lead to high uncertainties, and the impact of deposition morphology. Finally, a simple empirical procedure is presented using the analytical results obtained in the commercial bentonite sample to evaluate methodological, roughness, and instrumental uncertainties in the SA/DSA-TXRF proposed methodology.