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D5987-96 – Standard Test Method Technical Guide
ASTM D5987‑96 (Reapproved 2015) provides a definitive test method for the determination of total fluorine in coal and coke. It utilizes pyrohydrolytic extraction to separate fluorine from the sample matrix, followed by quantification via ion‑selective electrode (ISE) or ion chromatography (IC). The method is validated for coals with an ash content of 37 % or less.
📐 Scope and Laboratory Requirements
The test method in ASTM D5987 is designed for the analysis of total fluorine in coal and coke. It was successfully tested on coals containing 37 % ash or less. Values stated in SI units are regarded as standard. Quality management must follow Guide D4621, and sample preparation must conform to Practices D2013 (coal) and D346 (coke). Specific safety statements are referenced in Note 4 of the standard.
| 📏 Parameter | 🎯 Specification / Requirement |
|---|---|
| ⛏️ Target Matrix | Coal and Coke |
| ⚖️ Ash Limit | ≤ 37 % |
| 🧪 Detection Methods | Ion Selective Electrode (ISE) or Ion Chromatography (IC) |
| 📦 Sample Prep. References | ASTM D2013 (Coal), ASTM D346 (Coke) |
⚙️ Pyrohydrolytic Extraction and Apparatus Essentials
The core of this test method relies on pyrohydrolytic extraction to separate total fluorine from the coal or coke matrix. The extracted pyrohydrolysate is then gravimetrically processed. A strict material constraint applies: all laboratory ware coming into contact with fluoride solutions must be made of polyethylene, polystyrene, or a heat‑resistant polymer such as polypropylene.
⚠️ Critical Material Constraint: Never use standard borosilicate glassware for fluoride solutions. All flasks, beakers, and storage bottles must be constructed from plastic (PE, PP, PS). Glass vials (10–30 mL capacity) with tightly fitting snap‑on plastic lids are acceptable only for temporary sample storage.
Reagent water must conform to ASTM D1193 to ensure low blank levels. Vials specifically listed are 10 to 30‑mL capacity with tightly fitting snap‑on plastic lids.
📊 Significance and Analytical Workflow
This method permits the quantitative measurement of fluorine content to evaluate potential emissions from coal combustion or conversion processes. When the sample is combusted under prescribed conditions, the fluorine is quantitatively released and retained in the pyrohydrolysate. Final determination is achieved using ISE or IC, providing flexibility for different laboratory setups.
| 🟦 Step | 📐 Description |
|---|---|
| 1. Sample Weighing | Weigh accurate test portion. |
| 2. Pyrohydrolysis | Separate fluorine from the matrix under high temperature. |
| 3. Gravimetric Processing | Collect and process the pyrohydrolysate. |
| 4. Determination | Analyze solution using ISE or IC. |
| 5. Calculation | Compute total fluorine per base calculation standards (e.g., D3180). |
💡 Method Validation Context: The procedure is technically aligned with Australian Standard AS 1038.10.4 and the research by Conrad and Brownlee (Analytical Chemistry, 1988), confirming its robustness for coal and coke matrices.
❓ Frequently Asked Questions
🔍 What is the principle behind the ASTM D5987‑96 test method?
The method employs pyrohydrolytic extraction to separate total fluorine from the coal or coke matrix. The resulting pyrohydrolysate is then analyzed using an ion‑selective electrode (ISE) or an ion chromatograph (IC) to determine the fluoride ion concentration.
⚡ What are the critical safety and material handling concerns?
Dedicated plasticware (polyethylene, polystyrene, or polypropylene) is mandatory for all fluoride solutions to avoid contamination or adsorption loss. Note 4 of the standard contains specific hazard statements. The user must establish appropriate safety and health practices.
📌 For what types of coal samples is this method validated?
The standard explicitly states that the analysis was successfully tested on coals containing