ISO 20289:2025

Overview

ISO 20289:2025 - Surface chemical analysis - Total reflection X‑ray fluorescence analysis of water - specifies a laboratory chemical method for routine TXRF (total reflection X‑ray fluorescence) analysis of water. The standard is aimed at technicians and testing laboratories (particularly those accredited to ISO/IEC 17025) performing high‑throughput elemental analysis of drinking water, surface water, groundwater, waste waters and eluates. It defines good practices, accuracy/precision considerations and reporting requirements for elemental determination using TXRF instrumentation.

Key technical topics and requirements

• Scope and applicability: Quantitative determination of elements dissolved in water using TXRF; does not cover sampling, dilution or pre‑concentration methods, nor health/safety or commercial aspects.
• Instrumentation and calibration: Requirements for instrument calibration, determination of instrumental limit of detection (LOD), and procedures for TXRF measurements and spectra fitting.
• Sensitivity, LOD and LOQ: Typical limits of quantification (LOQ) for drinking and relatively unpolluted waters lie between 0.001 mg/L and 0.01 mg/L for most elements. The measurable concentration range typically spans 0.001 mg/L to 10 mg/L, depending on matrix and element.
• Interferences and matrix effects: Guidance on minimizing interferences (conductivity < 2 mS/cm recommended), handling suspended solids, peak overlaps, pile‑up/sum peaks and reagent/blank contamination.
• Sample preparation and labware: Specifications for clean labware, carrier preparation, drying apparatus options (infrared lamp, heating plate, vacuum vessel) and control of environmental contamination.
• Internal standard and validation examples: Use of internal calibration standards; Annex B provides a validation example using a Mo X‑ray source and Ga as internal standard.
• Quality assurance: Procedures for replicates, quality control samples, precision and accuracy checks, uncertainty estimation (Annex A), and required content for test reports.

Practical applications and users

• Environmental and public‑health laboratories performing routine elemental analysis of water (drinking water compliance, surface/groundwater monitoring).
• Wastewater testing facilities and laboratories analyzing eluates where TXRF advantages (surface sensitivity, small sample volumes) are relevant.
• Laboratories seeking methods compatible with ISO/IEC 17025 accreditation that need standardized TXRF workflows, validation examples and uncertainty calculation guidance.

Related standards

• ISO/TS 18507:2015 - Use of TXRF in biological and environmental analysis (referenced normative guidance).
• ISO/IEC 17025 - Laboratory competence and quality management for routine testing laboratories.

Keywords: ISO 20289, TXRF, total reflection X‑ray fluorescence, water analysis, elemental analysis, limit of quantification, ISO/IEC 17025, method validation, instrument calibration, laboratory quality control.