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D5085-21 – Standard Test Method Technical Guide
🧪 Scope and Method Detection Limits
This test method, designated D5085-21, is applicable to the determination of chloride, nitrate, and sulfate in atmospheric wet deposition samples (rain, snow, sleet, and hail) by suppressed ion chromatography. The concentration ranges were confirmed using an interlaboratory collaborative test. The validated method detection limits (MDLs) based on single operator precision and ranges are as follows:
| 🟦 Analyte | 📏 MDL (mg/L) | 🎯 Range of Method (mg/L) | ⚡ Range Tested (mg/L) |
|---|---|---|---|
| Chloride | 0.03 | 0.09 – 2.0 | 0.15 – 1.36 |
| Nitrate | 0.03 | 0.09 – 5.0 | 0.15 – 4.92 |
| Sulfate | 0.03 | 0.09 – 8.0 | 0.15 – 6.52 |
The MDL was determined following the guidance in 40 CFR Part 136 Appendix B. Different approaches to determining MDLs may yield different results.
⚠️ Critical Note on MDL Application: The precision and bias data presented in the standard are insufficient to statistically justify use at the published low MDL levels. However, it has been reported that this test method is reliable at lower levels than those explicitly tested in the collaborative study.
⚙️ Analytical Variables and Quality Assurance
Users must recognize that Method Detection Limits in ion chromatography are highly dependent on the specific configuration of the analytical system. Key variables that influence MDLs include:
- Column Specifications: The type and length of the column(s) used.
- Eluent Chemistry: The composition and strength of the eluent.
- System Configuration: Microbore versus standard bore instrumentation.
- Operating Parameters: Eluent flow rate and other instrument variables.
The MDLs listed in the table are those used specifically to determine the Precision and Bias of the method. The standard comprehensively references related ASTM practices for quality control, including D2777 for precision and bias determination, D4210 for intralaboratory quality control, and D5012 for the preparation of materials used for the collection and preservation of atmospheric wet deposition.
💡 Practical Guidance: For broader applications of suppressed ion chromatography for anion analysis, including alternative matrices, refer to Test Method D4327 (Anions in Water by Suppressed Ion Chromatography). This standard is the foundational methodology from which D5085-21 is derived.
📊 Referenced Documents and Standardization
ASTM D5085-21 relies on several key ASTM documents to provide a comprehensive analytical framework. This international standard was developed in accordance with internationally recognized principles on standardization established by the World Trade Organization Technical Barriers to Trade (TBT) Committee. Critical referenced standards include:
- D1129 / D1356: Terminology standards relating to Water and the Sampling and Analysis of Atmospheres.
- D1193: Specification for Reagent Water, ensuring appropriate water purity for analysis.
- D4327: Test Method for Anions in Water by Suppressed Ion Chromatography.
- D5012: Practice for Preparation of Materials Used for the Collection and Preservation of Atmospheric Wet Deposition.
- E694: Specification for Laboratory Glass Volumetric Apparatus.
It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices. Specific precautionary statements are given in Section 9 of the standard.
❓ Frequently Asked Questions
🔍 What types of samples are covered by the scope of D5085-21?
This test method is specifically applicable to the determination of chloride, nitrate, and sulfate in atmospheric wet deposition samples, including rain, snow, sleet, and hail.
💡 What are the validated method detection limits and concentration ranges?
The MDL for chloride, nitrate, and sulfate is 0.03 mg/L. The validated ranges of the method are 0.09 – 2.0 mg/L for chloride, 0.09 – 5.0 mg/L for nitrate, and 0.09 – 8.0 mg/L for sulfate.
⚡ What