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D6328-18 – Standard Test Method Technical Guide
📋 Scope and Application
This guide, designated D6328-18, is under the jurisdiction of ASTM Committee D22 on Air Quality and provides QA protocols for chemical analysis of atmospheric wet deposition (AWD). It covers anions (chloride, nitrate, and sulfate) and cations (calcium, magnesium, potassium, and sodium) as per Table 1 of the standard, along with pH. The guide is applicable to non-urban monitoring per D5111 and sets minimum requirements for calibration, validation, and QA sample frequency based on expected concentration ranges in AWD from Appendix X1.
⚙️ Quality Assurance Protocols
The QA protocols in D6328-18 emphasize systematic quality control. Key elements include preparation of calibration standards per Practice E200, use of reagent water conforming to D1193, and regular analysis of blanks, duplicates, and control samples. The guide recommends at least one blank, one duplicate, and one control sample per analytical batch. QA data should be evaluated using control charts to monitor accuracy and precision over time. Additionally, field blanks and trip blanks are recommended per D5111 for comprehensive field quality assurance.
📊 Analytical Methods and Validation
Table 1 lists the recommended methods for each analyte. Calibration must be performed using NIST‑traceable standards, and validation requires independent quality control solutions. Control charts must be maintained for ongoing verification of measurement performance.
| 🧪 Analyte | 📏 Method | 🎯 Standard |
|---|---|---|
| Chloride, Nitrate, Sulfate | Ion Chromatography (Chemically Suppressed) | D5085 |
| Calcium, Magnesium, Potassium, Sodium | Flame Atomic Absorption Spectrophotometry | D5086 |
| pH | Electrometric | D5015 |
All calibration standards should be prepared fresh and stored according to Practice E200. Acceptance criteria for precision and accuracy should be based on historical laboratory performance and method validation data.
💡 Use reagent water meeting D1193 Type I specifications for all solution preparations to minimize contamination at trace levels typical of AWD.
⚠️ Users must establish appropriate safety and environmental practices as described in Section 1.6 and refer to D3856 for laboratory management systems.
❓ Frequently Asked Questions
🔍
What are the main calibration requirements?
Calibration standards must be prepared according to Practice E200 using reagent water from D1193 and should cover the expected concentration ranges from Appendix X1. At least one standard should be verified with an independent source.
💡
Why are QA samples important in AWD analysis?
QA samples help validate accuracy and precision, which is essential for tracking long-term environmental changes and ensuring data comparability across monitoring studies.
⚡
What methods are used for anion analysis in AWD?
Test Method D5085 using chemically suppressed ion chromatography is recommended for chloride, nitrate, and sulfate determination in atmospheric wet deposition.
📌
How should QA data be evaluated?
QA data should be evaluated using control charts with established acceptance criteria. Any out-of-control points must be investigated and corrective actions taken before reporting results.