Summary of ISO standard 20289: Total reflection X-ray fluorescence analysis of water

The International Standard Organization (ISO) 20289 provides a method for determining the elemental concentration of impurities dissolved in water samples. It exploits total reflection X-ray fluorescence (TXRF) spectroscopy to measure a dried residue on an X-ray reflector. The scope is to provide a chemical metrology for quantitative analysis to obtain traceable results within a defined degree of accuracy and precision according to good practice and in compliance with ISO 17025. Target users include technicians working in laboratories who perform routine analysis of large numbers of samples. The method is specifically focused on determining elements dissolved in drinking, surface and ground water, but it can be also extended to waste waters and eluates if dilution steps are considered. The standard includes the description of all reagents, standards, and materials, including suitable reference materials, which are needed to prepare the sample and ensure quality assurance and control protocols. In addition, the standard presents a detailed description of sample preparation, contributions factors affecting the uncertainty budget, the general procedure to check instrumental calibration, determining limits of detection and quantification, and methods for spectra fitting.