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D3867-16 – Standard Test Method Technical Guide
🎯 Scope and Test Method Selection
ASTM D3867‑16 (Reapproved 2021) provides standard test methods for the determination of nitrite nitrogen, nitrate nitrogen, and combined nitrite‑nitrate nitrogen in water and wastewater. These methods are applicable to surface, saline, waste, and ground waters, with a working range from 0.05 to 1.0 mg/L nitrogen. The standard was editorially updated in November 2021, including the addition of the WTO caveat and updated warning notes throughout.
| 🟦 Test Method | 📏 Sections | 🎯 Key Principle |
|---|---|---|
| Test Method A – Automated Cadmium Reduction | 9 to 18 | Automated reduction of nitrate to nitrite using a copper‑coated cadmium column, followed by automated colorimetric analysis via diazotization. |
| Test Method B – Manual Cadmium Reduction | 19 to 28 | Manual column reduction through copper‑coated cadmium granules, with manual spectrophotometric determination of the resulting azo dye. |
⚙️ Analytical Procedure and Safety
Both methods rely on the reduction of nitrate ions to nitrite ions using a copper‑coated cadmium column. The total nitrite is then determined by diazotizing the sample to form a highly colored azo dye, which is measured spectrophotometrically. The selection between automated and manual methods is driven by laboratory throughput requirements and available instrumentation.
⚠️ Critical Safety Notice: The standard mandates the establishment of appropriate safety, health, and environmental practices. Specific hazard statements are provided in Section 8.2. Users must thoroughly review these requirements before beginning any analysis.
| ⚡ Key Referenced Standard | 📐 Application in D3867 |
|---|---|
| D1129 | Terminology Relating to Water |
| D1193 | Specification for Reagent Water |
| D2777 | Precision and Bias of D19 Test Methods |
| D5810 | Guide for Spiking into Aqueous Samples |
| D5847 | Writing QC Specifications for Water Analysis |
📊 Quality Control and Performance
Precision and bias for these test methods were established through interlaboratory studies conducted in accordance with Practice D2777. Laboratories must adhere to the quality control specifications outlined in Practice D5847. The use of reagent water meeting Specification D1193 is critical, and sample spikes performed per Guide D5810 are recommended for validating the performance of the analytical matrix.
💡 Laboratory Optimization: The cadmium columns require careful activation and regular maintenance to ensure complete reduction of nitrate to nitrite. Method detection limits are best optimized by strict adherence to the specific procedures detailed in Sections 9‑18 (Automated) or 19‑28 (Manual).
❓ Frequently Asked Questions
🔍 What is the fundamental principle of the cadmium reduction method?
A filtered sample is passed through a column containing copper‑coated cadmium granules. Nitrate is reduced to nitrite, and the total nitrite is determined by a diazotization reaction forming a colored azo dye.
💡 What is the working concentration range of the standard?
The standard specifically covers the range from 0.05 to 1.0 mg/L nitrogen for nitrite, nitrate, and combined nitrite‑nitrate in water.
⚡ Which two specific test methods does D3867‑16 provide?
Test Method A – Automated Cadmium Reduction (Sections 9 to 18) and Test Method B – Manual Cadmium Reduction (Sections 19 to 28).
📌 To which water matrices are these test methods applicable?
They are applicable to surface, saline, waste, and ground waters. It is the responsibility of the user to ensure the validity of these test methods for waters of untested matrices.