ISO 20289:2018 provides a chemical method for technicians working with Total Reflection X-ray Fluorescence (TXRF) instrumentation to perform measurements of water samples, according to good practices, with a defined degree of accuracy and precision. Target users are identified among laboratories performing routine analysis of large numbers of samples, which also comply with ISO/IEC 17025.
ISO 20289:2018 specifies a method to determine the content of elements dissolved in water (for example, drinking water, surface water and ground water). Taking into account the specific and additionally occurring interferences, elements can also be determined in waste waters and eluates. Sampling, dilution and pre-concentration methods are not included in this document.
Elements that can be determined with the present method may change according to the X-ray source of the instrument. No health, safety or commercial aspects are considered herewith.
The working range depends on the matrix and the interferences encountered. In drinking water and relatively unpolluted waters, the limit of quantification lies between 0,001 mg/l and 0,01 mg/l for most of the elements. The working range typically covers concentrations between 0,001 mg/l and 10 mg/l, depending on the element and predefined requirements.
Annex B reports, for example, the complete validation of the method of TXRF analysis of water performed with instrumentation that has Mo as the X-ray source and uses Ga as the internal standard for calibration.
Quantification limits of most elements are affected by blank contamination and depend predominantly on the laboratory air-handling facilities available, on the purity of reagents and the cleanliness of labware.