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D4326-21 – Standard Test Method Technical Guide
📐 Sample Preparation and Ashing Procedure
The test method requires that the coal sample be ashed under standard conditions and ignited to constant mass. For previously ashed materials, they are also ignited to constant mass under standard conditions. The resulting ash is then fused with lithium tetraborate (Li2B4O7) or an alternative suitable flux. The fused mixture is subsequently ground and pressed into a pellet or cast into a glass disk. This preparation ensures a homogeneous sample suitable for XRF analysis.
⚙️ XRF Analysis and Elemental Detection
The prepared pellet or glass disk is irradiated by an X-ray beam of short wavelength (high energy). The absorption of primary X-rays causes the emission of characteristic X-rays from the atoms in the sample. These fluorescent X-rays are dispersed and their intensities at selected wavelengths are measured using sensitive detectors. The detector output is then correlated to the mass fraction of elements via calibration curves or through computerized data-handling systems. The K spectral lines are utilized for all elements determined in this procedure.
📊 Key Measured Elements and Reporting
All elements are determined as the element and reported as the oxide. The elements covered in this test method include silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), phosphorus (P), titanium (Ti), manganese (Mn), strontium (Sr), and barium (Ba). Note that while manganese, strontium, and barium are not always included in the present method, their determination may be required to yield adequate totals. The values stated in SI units are to be regarded as standard, with values in parentheses provided for information only.
| 🟦 Element | 📏 Symbol | 📐 Oxide Form |
|---|---|---|
| Silicon | Si | SiO2 |
| Aluminum | Al | Al2O3 |
| Iron | Fe | Fe2O3 |
| Calcium | Ca | CaO |
| Magnesium | Mg | MgO |
| Sodium | Na | Na2O |
| Potassium | K | K2O |
| Phosphorus | P | P2O5 |
| Titanium | Ti | TiO2 |
| Manganese | Mn | MnO |
| Strontium | Sr | SrO |
| Barium | Ba | BaO |
Tip: This test method does not include sulfur determination. For sulfur analysis, refer to Test Method D5016. Ensure that all referenced documents are consulted for comprehensive testing.
Warning: Adhere to safety, health, and environmental practices as described in Section 1.3. Users must determine applicability of regulatory limitations prior to use.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D4326-21?
This test method covers the analysis of commonly determined major and minor elements in ash from coal using X-ray fluorescence (XRF) techniques. It includes elements such as Si, Al, Fe, Ca, Mg, Na, K, P, Ti, Mn, Sr, and Ba.
💡 How is the coal ash sample prepared?
The coal is ashed under standard conditions, ignited to constant mass, and fused with lithium tetraborate or other suitable flux. The mixture is then ground and pressed into a pellet or cast into a glass disk for XRF analysis.
⚡ Which spectral lines are used in this method?
The K spectral lines are used for all elements determined by this procedure, ensuring consistent and accurate detection.
📌 What elements are reported as oxides?
Elements reported as oxides include Si (SiO2), Al (Al2O3), Fe (Fe2O3), Ca (CaO), Mg (MgO), Na (Na2O), K (K2O), P (P2O5), Ti (TiO2), Mn (MnO), Sr (SrO), and Ba (BaO).