ASTM D7280 Quinoline-Insoluble (QI) Content Testing in Tar & Pitch
ASTM D7280 covers the evaluation of materials with quinoline insoluble ranging from 0 to 20 wt. % in round robin testing. The data should be stated in SI units to be regarded as standard.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
Overview
ASTM D7280 describes a test method for determining the quinoline insoluble (QI) content of coal tar, pitch, and related materials using stainless steel crucible filtration. QI consists of primary carbon particles and other high-molecular-weight insoluble material suspended in pitch, and its content significantly influences pitch processing, binder performance in carbon and graphite products, and anode quality in aluminum smelting.
Accurate QI determination is critical for pitch suppliers, carbon product manufacturers, and aluminum producers to ensure consistent electrode and refractory binder performance.
Scope, Applications, and Benefits
Scope
ASTM D7280 applies to coal tar pitch, modified pitch, and tar products and determines:
- Quinoline insoluble (QI) content as weight percent of total pitch
- Contribution of primary QI (alpha particles) to electrode porosity and structure
- Comparability with ISO methods for international trade applications
- Effect of QI on pitch softening point and processability
Applications
- Aluminum smelter anode binder pitch quality control
- Graphite electrode pitch binder specification compliance
- Carbon and graphite refractory binder characterization
- Coal tar distillation pitch quality assurance
- Research on pitch structure and electrode performance
Benefits
- More precise than Gooch crucible filtration method
- Stainless steel crucible provides consistent pore size and reusability
- Applicable to a wide range of pitch types and viscosities
- Provides reproducible data for international pitch trade
- Supports electrode quality and performance optimization
Test Process
Sample Dissolution
A weighed pitch sample is dissolved in hot quinoline to solubilize all non-QI components.
1Filtration
The hot solution is filtered through a tared stainless steel crucible; QI particles are retained on the crucible filter.
2Washing and Drying
The crucible is washed with hot quinoline to remove residual pitch, then dried to constant mass in an oven.
3QI Calculation
QI content is the crucible mass gain after filtration divided by the sample mass, expressed as wt%.
4Technical Specifications
| Parameter | Details |
|---|---|
| Standard | ASTM D7280 |
| Test Principle | Hot quinoline extraction and stainless steel crucible filtration |
| Applicable Materials | Coal tar pitch, tar, modified pitch |
| Dissolution Temperature | 75–80°C for quinoline dissolution |
| Crucible Type | Stainless steel with defined pore size |
| Measured Output | QI content (wt%) |
Instrumentation Used for Testing
- Stainless steel filtration crucibles (defined pore size)
- Hot plate or heating mantle for quinoline dissolution
- Vacuum filtration apparatus
- Analytical balance (0.1 mg resolution)
- Drying oven (105°C)
- Quinoline solvent (reagent grade)
Results and Deliverables
- QI content (wt%) with replicate values
- Precision data compared to method repeatability limits
- Comparison to pitch specification or historical data
- Test report with sample identification and method details
- Certificate of analysis for pitch lot acceptance
Why Choose Infinita Lab for ASTM D7280?
Infinita Lab is a trusted USA-based testing laboratory offering ASTM D7280 testing services across an extensive network of accredited facilities across the USA.
Infinita Lab is built to serve the full spectrum of modern testing needs—across industries, materials, and methodologies. Our advanced equipment and expert professionals deliver highly accurate and prompt test results, helping businesses achieve quality compliance and product reliability.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote
Frequently Asked Questions
QI consists primarily of free carbon particles (alpha carbon), high-molecular-weight condensed ring compounds, and inorganic ash that do not dissolve in quinoline solvent at 75°C.
QI in anode binder pitch forms a carbon skeleton during baking; appropriate QI levels contribute to anode density and strength, while excessive QI can increase porosity and reduce anode performance.
D7280 uses a stainless steel crucible with more consistent pore size and improved reproducibility compared to the asbestos Gooch crucible method, and is compatible with international ISO standards.
Yes — quinoline is toxic and requires appropriate ventilation, PPE, and waste disposal; testing should be conducted in a properly equipped laboratory fume hood following safety protocols.
Aluminum anode binder pitches typically specify QI between 6–12%; graphite electrode pitches may require lower QI (1–5%) for better impregnation of graphite pores.
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