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D5790-18 – Standard Test Method Technical Guide
📐 Scope and Applicable Matrices
ASTM D5790‑18 specifies a standard test method for the identification and simultaneous measurement of purgeable volatile organic compounds in water. This method has been rigorously validated for treated drinking water, wastewater, and ground water. The standard relies on purge‑and‑trap sample introduction coupled with capillary column gas chromatography/mass spectrometry (GC/MS).
⚠️ User Responsibility: While the method is validated for specific aqueous matrices, its applicability to other matrices must be conclusively demonstrated by the user. It is also the responsibility of the user to establish appropriate safety, health, and environmental practices in accordance with regulatory limitations.
The method is ideal for compounds with high volatility and low water solubility. Analytes that are inefficiently purged may not be detected at low concentrations, but can be accurately measured when present in sufficient amounts. Analyte concentrations up to approximately 200 µg/L can be determined without the need for sample dilution.
⚙️ Test Procedure and Data Reporting Specifications
The GC/MS procedure relies on capillary column chromatography for separation. Analytes that coelute but possess different mass spectra and non‑interfering quantitation ions can be identified and measured in the same run. However, compounds with very similar mass spectra (such as structural isomers) cannot be individually identified unless they are chromatographically resolved. If unresolved, they must be reported as an isomeric group or pair. For example, two of the three isomeric xylenes typically coelute on standard capillary columns and must be reported as an isomeric pair.
💡 Technical Note: The values stated in SI units are regarded as standard. No other units of measurement are included in this standard. This international standard was developed in accordance with globally recognized standardization principles.
| 🧪 Compound Category | 📏 Reporting Rule | ⚡ Concentration Limit |
|---|---|---|
| Coeluting Analytes (Different Spectra) | Identified separately using quantitation ions | ~200 µg/L |
| Coeluting Structural Isomers (Similar Spectra) | Reported as isomeric group or pair | ~200 µg/L |
| Inefficiently Purged Analytes | May not be detected at low concentrations | Varies by compound |
❓ Frequently Asked Questions
🔍 What types of water are directly validated under D5790‑18?
This test method has been validated for treated drinking water, wastewater, and ground water. Testing other aqueous matrices requires a demonstration of validity by the user.
💡 What is the maximum concentration for direct analysis without dilution?
Analyte concentrations up to approximately 200 µg/L may be determined without dilution. Analytes present at very low concentrations that are inefficiently purged may not be detected.
⚡ How must coeluting isomers like xylene isomers be reported?
If two or more structural isomers (e.g., two of the three isomeric xylenes) are not resolved by the capillary column, they cannot be individually identified and must be reported as an isomeric pair or group.
📌 What are the required units of measurement for this standard?
The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.