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D6357-21 – Standard Test Method Technical Guide
🧪 Scope and Analytics Covered
ASTM D6357-21b provides standard test methods for the determination of antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, lead, manganese, molybdenum, nickel, vanadium, and zinc in coal and coke. These methods are also applicable to the analysis of residues derived from coal combustion processes. Furthermore, specific procedures for the determination of rare earth elements (REEs) in coal and coal combustion residues are detailed.
| 🟦 Analytic Group | 📏 Elements Covered |
|---|---|
| Priority Trace Elements (Coal & Coke) | Antimony, Arsenic, Beryllium, Cadmium, Chromium, Cobalt, Copper, Lead, Manganese, Molybdenum, Nickel, Vanadium, Zinc |
| Rare Earth Elements (Coal & Combustion Residues) | Cerium, Dysprosium, Erbium, Europium, Gadolinium, Holmium, Lanthanum, Lutetium, Neodymium, Praseodymium, Samarium, Scandium, Terbium, Thulium, Ytterbium, Yttrium |
💡 Technical Note: As per Note 1 of the standard, these test methods may be applicable to the determination of other trace elements beyond the specific list, pending appropriate validation against the sample matrix.
⚙️ Test Procedure and Analytical Platforms
The summary of the test method (Section 4) requires that a representative sample of coal or coke is first ashed under controlled conditions. The resulting ash is then subjected to a rigorous acid digestion using a mixture of aqua regia and other mineral acids to bring the analytes into solution.
The standard explicitly allows for three powerful instrumental techniques for the quantitation of the dissolved elements:
- Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
- Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
- Graphite Furnace Atomic Absorption Spectrometry (GFAAS)
| ⚡ Instrument | 🎯 Typical Application |
|---|---|
| ICP-AES | Multi-element analysis of major/minor trace elements |
| ICP-MS | Ultra-trace analysis and quantification of rare earth elements |
| GFAAS | High-sensitivity determination of single elements (e.g., Pb, As) |
📌 Safety Caution: As stated in Section 1.3, this standard does not purport to address all safety concerns. Users must establish appropriate safety, health, and environmental practices for handling high-temperature ashing furnaces and concentrated acid digestion mixtures.
📐 Units and Regulatory Framework
The values stated in SI units are to be regarded as the standard for D6357-21b. All percentages reported are percent mass fractions unless otherwise noted. The standard references key ASTM practices for sample preparation (D2013 for coal, D346 for coke), moisture and ash determination (D3173, D3174, D7582), and laboratory competence (D7448). It was developed in accordance with internationally recognized principles on standardization as outlined by the WTO TBT Committee.
❓ Frequently Asked Questions
🔍 What is the primary scope of ASTM D6357-21b?
It covers the determination of trace elements (including antimony, arsenic, cadmium, lead, etc.) and rare earth elements (such as cerium, lanthanum, and yttrium) in coal, coke, and combustion residues from coal utilization processes.
💡 Which analytical techniques can be used under this standard?
The standard permits three techniques: Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Graphite Furnace Atomic Absorption Spectrometry (GFAAS).
⚡ How should the coal sample be prepared for analysis?
The sample must be prepared according to Practices D2013 or D346, ashed under controlled conditions, and then digested using a mixture of aqua regia and other specified acids.
📌 Are there specific requirements for laboratory competence?
Yes, the standard references Practice D7448, which establishes criteria for the competence of laboratories performing sampling and analysis of coal and coke.