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BS EN ISO 14720 — Testing of Ceramic Raw and Basic Materials Determination of Sulfur in Powders and Granules Standard Series
Testing of Ceramic Raw and Basic Materials — Determination of Sulfur (2013 Edition)
🧪 BS EN ISO 14720 is a method standard for the determination of sulfur in ceramic raw and basic materials (especially refractories), developed jointly by ISO/TC 33 “Refractories” and CEN/TC 187 “Refractory products and materials” and published in the UK by BSI as a British Standard. The series specifies methods for determining sulfur in powders and granules of non-oxidic ceramic raw and basic materials, serving quality inspection and process control of refractories and ceramic raw materials.
💡 Sulfur is a harmful impurity in ceramics and refractories: at high temperatures, sulfur-bearing components can cause cracking, erosion, and disturb the furnace atmosphere. Accurate sulfur determination is essential for raw-material acceptance and process control.
1. Series Overview 📌
The BS EN ISO 14720 series comprises two parts, both published by BSI in 2013. Part 1 specifies the infrared measurement method; Part 2 specifies ICP/OES or ion chromatography after burning in an oxygen flow. UK participation was entrusted to Technical Committee RPI/1 (Refractory products and materials).
2. Series Structure and Scope 🧩
The parts and their scopes are shown below. The series applies to powder and granule samples of non-oxidic ceramic raw and basic materials (e.g., silicon carbide, silicon nitride, graphite).
| Standard | Title | Core Content | Typical Use |
|---|---|---|---|
| BS EN ISO 14720-1:2013 | Testing of ceramic raw and basic materials — Determination of sulfur in powders and granules of non-oxidic materials — Part 1: Infrared measurement methods | Combustion in oxygen flow, sulfur oxides quantified by infrared absorption | Rapid sulfur determination for refractories and ceramic raw materials |
| BS EN ISO 14720-2:2013 | Testing of ceramic raw and basic materials — Determination of sulfur in powders and granules of non-oxidic materials — Part 2: ICP/OES or ion chromatography after burning in an oxygen flow | Combustion followed by absorption; quantification by ICP/OES or ion chromatography | Precise quantification of low sulfur, multi-element analysis |
⚠️ Sample preparation and combustion conditions are critical: non-oxidic materials (e.g., SiC, Si₃N₄) must be fully oxidized during high-temperature combustion in an oxygen flow, otherwise incomplete sulfur release gives low results. Control combustion temperature, time, and flux strictly as specified.
3. Infrared Measurement Method (Part 1) 🔍
BS EN ISO 14720-1 specifies the infrared (IR) measurement method for sulfur, mainly covering:
- Principle: the sample is combusted at high temperature in an oxygen flow; sulfur is converted to SO₂ (with some SO₃), quantified by an infrared detector.
- Sample handling: requirements for particle size, sample mass, flux (e.g., tungsten-tin), and crucibles.
- Calibration: establish a calibration curve using certified reference materials to ensure traceable results.
- Range and precision: applicable sulfur range, repeatability, and reproducibility limits.
4. ICP/OES or Ion Chromatography (Part 2) ⚖️
BS EN ISO 14720-2 specifies methods to quantify sulfur after burning in an oxygen flow:
- Combustion and absorption: the sample is combusted in an oxygen flow; the sulfur oxides formed are absorbed into an absorption solution.
- ICP/OES quantification: sulfur in the absorption solution is measured by inductively coupled plasma optical emission spectrometry, suitable for low contents and multi-element analysis.
- Ion chromatography quantification: sulfate (SO₄²⁻) in the absorption solution is measured by ion chromatography for high-precision sulfur quantification.
- Method selection: choose the method by sulfur level and laboratory capability; the two methods can cross-verify each other.
| Method | Principle | Feature | Applicable Sulfur Level |
|---|---|---|---|
| Infrared (Part 1) | IR absorption after combustion | Fast, automated, suitable for high throughput | Higher content (% level) |
| ICP/OES (Part 2) | Plasma optical emission | Multi-element, sensitive at low levels | Low to trace |
| Ion chromatography (Part 2) | Chromatographic separation of SO₄²⁻ | High precision, good selectivity | Low content (ppm level) |
✅ Selection guidance: use the infrared method (Part 1) for rapid raw-material acceptance; use ICP/OES or ion chromatography (Part 2) for precise low-content determination, arbitration, or R&D, and cross-check between methods when needed.
5. Engineering Practice 🛠️
- 🔍 Raw-material acceptance: perform sulfur inspection on silicon carbide, silicon nitride, graphite, and other raw materials to ensure compliance with purchase specifications.
- 🔧 Process control: monitor sulfur variation in raw materials to prevent furnace-atmosphere contamination and product defects.
- 📊 Method comparison: conduct inter-laboratory comparisons and proficiency testing to ensure consistent results.
- 📋 Quality control: verify instrument condition regularly with reference materials and maintain quality control charts.
6. Precision and Quality Control 📏
The reliability of sulfur determination is directly linked to the precision of the method. The standard typically gives repeatability (within-laboratory, same operator, same instrument) and reproducibility (between laboratories) limits. In practice, results are assured through the following measures:
- 🔬 Certified reference materials: establish the calibration curve and re-check it regularly with CRMs to ensure traceable results.
- 🧪 Replicates and blanks: run duplicate samples and blanks with each batch to monitor drift and contamination.
- 📊 Quality control charts: measure QC samples periodically and maintain mean-range control charts to detect anomalies.
- 🤝 Proficiency testing: participate in inter-laboratory comparisons to validate the method in the laboratory.
For low-content sulfur (e.g., ppm level), prefer the ICP/OES or ion chromatography method (Part 2) owing to its low detection limit and good selectivity; for higher contents or high throughput, the infrared method (Part 1) is more efficient. The two methods can cross-verify: if the difference exceeds the reproducibility limit, investigate sample preparation, combustion conditions, and calibration status.
7. Frequently Asked Questions ❓
❓ Q: Why must non-oxidic materials be combusted to determine sulfur?
A: Sulfur exists in different chemical states; only by high-temperature combustion in an oxygen flow to fully convert it to sulfur oxides (SO₂/SO₃) and absorb them can it be quantified by IR, ICP/OES, or ion chromatography, ensuring representative results.
A: Sulfur exists in different chemical states; only by high-temperature combustion in an oxygen flow to fully convert it to sulfur oxides (SO₂/SO₃) and absorb them can it be quantified by IR, ICP/OES, or ion chromatography, ensuring representative results.
❓ Q: How is the infrared method vs. ICP/OES/ion chromatography chosen?
A: The infrared method is fast and automated, suited to higher contents and high throughput; ICP/OES and ion chromatography are sensitive and selective, suited to low contents and arbitration. Choose by sulfur level and need, or cross-check.
A: The infrared method is fast and automated, suited to higher contents and high throughput; ICP/OES and ion chromatography are sensitive and selective, suited to low contents and arbitration. Choose by sulfur level and need, or cross-check.
❓ Q: How is measurement accuracy ensured?
A: Calibrate with certified reference materials, control combustion conditions (temperature, time, flux), perform replicates and blanks, and verify instrument condition regularly.
A: Calibrate with certified reference materials, control combustion conditions (temperature, time, flux), perform replicates and blanks, and verify instrument condition regularly.
🔍 Q: Which materials does the series cover?
A: Powders and granules of non-oxidic ceramic raw and basic materials such as silicon carbide, silicon nitride, borides, graphite, and carbonaceous refractories.
A: Powders and granules of non-oxidic ceramic raw and basic materials such as silicon carbide, silicon nitride, borides, graphite, and carbonaceous refractories.