Overview
ISO 4722-2:2024 - Water Quality - Thorium 232 - Part 2: Test Method using ICP-MS establishes a standardized procedure for determining thorium-232 (232Th) concentrations in various water types using inductively coupled plasma mass spectrometry (ICP-MS). This international standard supports consistent, reliable results, crucial for environmental monitoring and compliance with health and regulatory guidelines associated with water quality and radioactivity.
This method is applicable to a range of water samples, including:
- Drinking water
- Rainwater
- Surface and ground water
- Marine water
- Industrial and domestic wastewater
- Cooling and process water
It is suitable for routine monitoring, regulatory compliance, emergency situations, and research purposes involving radiological water analysis.
Key Topics
Scope of Measurement
- ISO 4722-2:2024 details the ICP-MS technique for measuring 232Th in filtered water samples.
- The standard outlines the procedure for converting measured mass concentrations to activity concentrations.
- Analytical range: Activity concentrations between approximately 2 mBq·L⁻¹ and 5 Bq·L⁻¹; higher concentrations may be measured after suitable dilution.
- The method’s limit of detection (~2 mBq·L⁻¹) is well below WHO guidelines for drinking water.
Sample Preparation and Handling
- Water samples must be filtered to remove suspended matter before analysis (analysis of particulates is not included under this method).
- All steps require clean laboratory protocols to avoid contamination, using ultrapure water and high-purity reagents.
- Proper acidification and storage are mandated to preserve sample integrity during transport.
Analytical Process
- Utilizes ICP-MS for high sensitivity and selectivity.
- Special attention to chemical interferences, particularly isobaric and polyatomic species, is necessary.
- Internal standards and chemical tracers are used for correction of recovery, matrix effects, and measurement bias.
- The method includes robust calibration protocols and requires regular background checks and instrument verification.
Quality Assurance
- Laboratories must demonstrate measurement competence (e.g., ISO/IEC 17025).
- Regular use of control and blank samples, as well as participation in inter-laboratory comparisons, is recommended.
- Written reports should include all relevant sample, calibration, and measurement details, as per standard requirements.
Applications
The ISO 4722-2:2024 standard provides practical value across multiple sectors:
- Drinking Water Safety: Supports regulatory authorities and water suppliers in confirming compliance with national and WHO guidance for radionuclide concentrations.
- Environmental Monitoring: Enables governmental and research organizations to monitor natural water bodies for radioactive contamination from both natural and anthropogenic sources.
- Industrial Compliance: Facilities that discharge water (e.g., nuclear plants, mining operations) can use the method to ensure emissions meet environmental standards.
- Emergency Response: Reliable for use during radiological incidents affecting water resources, ensuring rapid and accurate assessment.
- Research: Facilitates academic and commercial research into environmental radioactivity and water treatment technologies.
Related Standards
The effective application of ISO 4722-2:2024 depends on a suite of supporting standards, including:
- ISO/IEC Guide 98-3: Uncertainty of measurement - Guide to the expression of uncertainty in measurement
- ISO 5667 Series:
- ISO/IEC 17025: General requirements for the competence of testing and calibration laboratories
- ISO 17294 Series:
- ISO 17294-1: General guidelines for ICP-MS in water analysis
- ISO 17294-2: Determination of selected elements by ICP-MS
- ISO 80000-10: Quantities and units for atomic and nuclear physics
By adhering to ISO 4722-2:2024, laboratories, regulatory authorities, and industry stakeholders can ensure accurate, reproducible results in thorium-232 water analysis, enhancing public and environmental health protection.
Keywords: ISO 4722-2, water quality, thorium-232, ICP-MS, radioactive analysis, environmental monitoring, drinking water standard, radiological emergency, water testing, international standard.