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D2593-23 – Standard Test Method Technical Guide
🔬 Scope and Application
This test method covers the determination of butadiene-1,3 purity and hydrocarbon impurities including propane, propylene, isobutane, n-butane, butene-1, isobutylene, propadiene, trans-butene-2, cis-butene-2, butadiene-1,2, pentadiene-1,4, and various acetylenes (methyl, dimethyl, ethyl, and vinyl) in polymerization grade butadiene. The method uses gas chromatography and is suitable for process quality control and specification setting.
Values are stated in SI units, and safety precautions are emphasized, including LPG safety training.
⚙️ Test Method and Apparatus
A representative sample is introduced into a gas-liquid partition column. Components are separated by an inert carrier gas and detected using a thermal-conductivity or flame ionization detector. The chromatogram is interpreted using attenuation and response factors to determine relative concentrations.
The chromatograph must have sufficient sensitivity and stability to produce a recorder deflection of at least 2 mm at a signal-to-noise ratio of at least 5:1 for 0.01% by mass of impurity.
| 🟦 Requirement | 📏 Specification |
|---|---|
| Detector Type | Thermal-conductivity or flame ionization |
| Minimum Deflection | 2 mm at S/N ≥ 5:1 |
| Impurity Detection Limit | 0.01% by mass |
📊 Key Impurities and Normalization
The test method identifies a wide range of impurities. Butadiene dimer, carbonyls, inhibitor, and residue are measured by other ASTM procedures and used to normalize the chromatographic results.
| 🎯 Impurity | ⚡ Analysis Method |
|---|---|
| Propane, Propylene | Gas chromatography |
| Isobutane, n-Butane | Gas chromatography |
| Butene-1, Isobutylene | Gas chromatography |
| Propadiene, trans-Butene-2, cis-Butene-2 | Gas chromatography |
| Butadiene-1,2 | Gas chromatography |
| Pentadiene-1,4 | Gas chromatography |
| Methyl, Dimethyl, Ethyl, Vinyl Acetylene | Gas chromatography |
| Butadiene Dimer, Carbonyls, Inhibitor, Residue | Other ASTM procedures |
💡 Tip: Ensure the chromatograph meets the sensitivity requirement of 2 mm deflection at S/N ≥5:1 for 0.01% impurity to ensure accurate detection.
⚠️ Warning: Users should obtain LPG safety training before performing this test method, as per section 1.3.1.
❓ Frequently Asked Questions
🔍 Q1: What is the scope of ASTM D2593-23?
A1: It covers the determination of butadiene-1,3 purity and hydrocarbon impurities in polymerization grade butadiene by gas chromatography.
💡 Q2: What detectors can be used?
A2: Both thermal-conductivity and flame ionization detectors are acceptable, provided they meet sensitivity criteria.
⚡ Q3: What is the required detection sensitivity?
A3: The system must achieve a recorder deflection of at least 2 mm at a signal-to-noise ratio of at least 5:1 for 0.01% by mass of impurity.
📌 Q4: How are impurities like butadiene dimer handled?
A4: They are measured by other ASTM procedures and results used to normalize the chromatographic distribution.