ASTM D7168-21 PDF

Overview

ASTM D7168-21 is a standard test method developed by ASTM International to measure the concentration of technetium-99 (^99Tc) in environmental water samples using solid phase extraction (SPE) disks. This method is designed for non-process-related or effluent water, such as surface water, groundwater, or tap water, and quantifies ^99Tc beta activity through liquid scintillation spectrometry. Accurate determination of radiochemical contaminants like technetium-99 is essential for environmental monitoring, water safety, and compliance with regulatory standards.

Key Topics

• Solid Phase Extraction (SPE): This standard describes a procedure in which technetium in water samples is selectively retained on an SPE disk, concentrating the analyte for subsequent measurement.
• Liquid Scintillation Spectrometry: After extraction, beta activity of technetium-99 is quantified using liquid scintillation counters, which offer high sensitivity for low-level radioactive measurements.
• Sample Range & Suitability: The method is validated for water samples with approximately 0.037 Bq/L (1.0 pCi/L) or greater in 1-liter samples. It has been used successfully for tap water, but users must verify suitability for other matrices or larger samples.
• Quality Assurance: The standard emphasizes robust quality control practices, including method blanks, laboratory control samples, duplicates, and calibration procedures using traceable standards.
• Detection and Interference: The method outlines steps to account for sample interferences, such as removal of suspended solids, treatment of organic matter, and managing interferences from other anionic radionuclides.
• Safety Considerations: Users are responsible for adhering to proper safety protocols for chemical and radiochemical handling, as well as conforming to regulatory requirements.

Applications

ASTM D7168-21 is widely applicable for:

• Environmental Monitoring: Supports regulatory compliance by enabling the detection of technetium-99 in drinking water, groundwater, and surface water, critical near nuclear facilities or waste repositories.
• Water Quality Assessment: Used by laboratories, environmental consultants, and public health organizations for routine surveillance and risk assessment of radiochemical contamination.
• Research and Development: Assists researchers in studying radionuclide transport in aquatic environments and assessing the fate of technetium-99 from anthropogenic or natural sources.
• Regulatory Reporting: Frequently referenced in regulatory frameworks to ensure that water supplies meet safety standards regarding radioactive isotopes.
• Comparison to Alternative Methods: While this method uses SPE and scintillation counting, related methods such as ASTM D8026 apply inductively coupled plasma mass spectrometry (ICP-MS) for ^99Tc analysis.

Related Standards

To ensure comprehensive water quality testing and consistency across laboratories, ASTM D7168-21 should be considered alongside related ASTM standards:

• ASTM D1129 - Terminology Relating to Water
• ASTM D1193 - Specification for Reagent Water
• ASTM D2777 - Practice for Determination of Precision and Bias
• ASTM D3370 - Practices for Sampling Water from Flowing Streams
• ASTM D4448 - Guide for Sampling Groundwater
• ASTM D5847 - Practice for Writing Quality Control Specifications
• ASTM D6001 - Guide for Direct-Push Groundwater Sampling
• ASTM D7282 - Practice for Setup, Calibration, and Quality Control of Instruments Used for Radioactivity Measurements
• ASTM D7902 - Terminology for Radiochemical Analyses
• ASTM D8026 - Practice for Determination of Tc-99 in Water by ICP-MS

Summary

ASTM D7168-21 is an essential standard for laboratories and environmental professionals involved in monitoring technetium-99 levels in water. Its solid phase extraction approach and detailed quality assurance guidelines support precise, reliable measurement of radiochemical contaminants, contributing to public health, environmental protection, and regulatory compliance.