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D2972-15 – Standard Test Method Technical Guide
ASTM Standard D2972−15 (Reapproved 2023) provides standardized procedures for the determination of arsenic in water and wastewater matrices. The standard encompasses three distinct analytical approaches—a colorimetric method and two atomic absorption methods—each optimized for specific concentration ranges and laboratory capabilities. Given the adverse physiological effects of arsenic from herbicides, insecticides, and industrial effluents, these methods are essential for environmental monitoring and regulatory compliance.
📐 Test Methods and Concentration Ranges
The standard is organized into three independent test methods, allowing laboratories to select the most appropriate technique based on the expected arsenic concentration and available instrumentation. The methods span a wide dynamic range suitable for various industrial effluent and natural water applications.
| 🟦 Method | 📏 Technique | 🎯 Concentration Range | 📄 Sections |
|---|---|---|---|
| A | Silver Diethyldithiocarbamate Colorimetric | 5 µg/L to 250 µg/L | 7 – 16 |
| B | Atomic Absorption, Hydride Generation | 1 µg/L to 20 µg/L | 17 – 26 |
| C | Atomic Absorption, Graphite Furnace | 5 µg/L to 100 µg/L | 27 – 36 |
The analyst must carefully review the precision and bias statements specific to each method, particularly when applying them to water matrices not explicitly evaluated during the standard’s validation. Values are expressed in SI units as the standard.
⚙️ Sample Preparation and Safety Considerations
Sample preparation is critical for achieving accurate “total recoverable arsenic” results. The standard defines this term as the arsenic forms recovered by its prescribed acid-digestion procedure. It is essential to note that some organic arsenic compounds, such as phenylarsonic acid, disodium methane arsonate, and dimethylarsonic acid, are not completely recovered during this step. Proper collection and holding time protocols are detailed in Practices D3370 and D4841.
⚠️ Critical Safety Note: The standard does not purport to address all safety concerns. Specific hazard statements are explicitly located in Section 11.1 (Test Method A reagents) and Section 20.2 (Test Method B reagents). It is the user’s responsibility to establish appropriate safety, health, and environmental practices prior to analysis.
📊 Quality Control and Method Performance
Quality control specifications must be established following Practice D5847. The laboratory is responsible for validating the method for the specific matrix being tested, utilizing sp