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D5317-20 – Standard Test Method Technical Guide
The ASTM D5317-20 standard defines a rigorous gas chromatographic (GC) procedure coupled with an electron capture detector (ECD) for the quantitative determination of specific chlorinated organic acid compounds and acidic herbicides in aqueous samples. This method provides a standardized framework for the analysis of compounds critical to environmental monitoring, specifically targeting the free acid form of several key analytes.
🧪 Scope and Analyte Specifications
The test method is validated for the quantitative determination of selected chlorinated acids and other acidic herbicides. While suitable for salts and esters of the target compounds, results are uniformly reported as the total free acid. The method was thoroughly interlaboratory tested using reagent water and finished tap water. Analysts must verify applicability for compounds not explicitly listed. The following analytes were certified through the interlaboratory study:
| 🟦 Analyte | 📐 CAS Registry Number |
|---|---|
| Bentazon | 25057-89-0 |
| 2,4-D | 94-75-7 |
| 2,4-DB | 94-82-6 |
| DCPA acid metabolites | — |
| Dicamba | 1918-00-9 |
| 3,5-Dichlorobenzoic acid | 51-36-5 |
| Dichlorprop | 120-36-5 |
| 5-Hydroxydicamba | 7600-50-2 |
| Pentachlorophenol (PCP) | 87-86-5 |
| Picloram | 1918-02-1 |
| 2,4,5-T | 93-76-5 |
| 2,4,5-TP (Silvex) | 93-72-1 |
📌 Key Distinction: This test method reports every result strictly as the total free acid. It does not differentiate between the parent acid, its esterified forms, or salt complexes. Ensure standards are prepared accordingly to reflect this reporting convention.
⚙️ Methodology Expertise and Quality Assurance
The standard restricts its use to analysts with proven experience in gas chromatography and the interpretation of gas chromatograms. Initial competency must be demonstrated per the procedure in Section 19.3. Sections 16.6, 16.7, and 16.8 explicitly state that chromatographically unresolved analytes (compounds with very similar retention times) cannot be quantified unless a secondary identification technique is employed. Furthermore, identification of any analyte in an unfamiliar sample matrix must be confirmed by at least one additional qualitative technique to ensure accuracy.
⚠️ Matrix Applicability Warning: The precision and bias data presented in Section 18 of this standard are specifically derived from the interlaboratory study on reagent water and finished tap water. Users are strongly cautioned against extrapolating this data to other sample matrices without conducting a thorough method validation.
📊 Standard Compliance and Reference Documents
Issued under the fixed designation D5317-20, this standard adheres to internationally recognized principles on standardization as set forth by the WTO TBT Committee. It is governed by relevant ASTM standards including D1129 (Terminology Relating to Water), D1193 (Specification for Reagent Water), and D2777 (Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19). Safety is of paramount concern; specific hazard warning statements are located in Sections 6, 8, 9, and 10 of the standard, placing the responsibility firmly on the user to establish safe operating practices.
❓ Frequently Asked Questions
🔍 What specific water matrices were used to validate this test method?
The interlaboratory validation study for D5317-20 was conducted using reagent water, as defined by ASTM D1193, and finished tap water. The reported precision and bias in Section 18 strictly apply to these matrices.
💡 How should the analyst report results for chlorinated esters or salts?
Analysts should report the concentration for each listed analyte as the total free acid equivalent. The test method does not provide differentiation among the acid, ester, or salt forms.
⚡ What is the required action if two target analytes co-elute?
Per Sections 16.6 through 16.8, co-eluting analytes with nearly identical retention times cannot be individually identified or measured in the same calibration mixture or sample unless a proven alternative technique for quantification is successfully applied.
📌 Why must unfamiliar samples undergo additional confirmation?
Section 1.6 mandates that when unfamiliar sample types are analyzed, all analyte identifications must be confirmed by at least one additional qualitative technique to guard against false positives and matrix interferences not encountered during initial validation.