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D5713-23 – Standard Test Method Technical Guide
ASTM D5713-23 defines a standardized procedure for capillary gas chromatography analysis of high-purity benzene intended for cyclohexane feedstock. This method is essential for quantifying specific impurities and verifying final product purity, supporting both process control and end-product certification within the aromatic chemicals industry. The standard is issued under the jurisdiction of ASTM Subcommittee D16.01.
📋 Scope and Applicability
This test method is applicable to benzene samples ranging from 99 % to 100 % purity. It is designed to detect and quantify individual impurities within a concentration range of 2 mg/kg to 10,000 mg/kg. The established Limit of Detection (LOD) for an impurity is 2 mg/kg, and the Limit of Quantitation (LOQ) is 6 mg/kg. All results must be rounded in accordance with the rounding-off method of Practice E29 to determine conformance with applicable specifications.
⚙️ Summary of Test Method and Calculation
The analyst adds a known amount of an internal standard, such as n-octane, to the benzene sample. Using capillary gas chromatography, the peak area of each impurity is measured and compared to the peak area of this internal standard. The concentration of each impurity is calculated based on the response factor of toluene relative to the internal standard, while a response factor of 1.00 is used for nonaromatic impurities. The total concentration of all detected impurities is then subtracted from 100.00 to determine the final benzene purity. The procedure adheres to established practices for gas chromatography, including Practices E260, E355, and E1510 for column installation and operation.
📊 Key Performance Metrics and Parameters
The table below summarizes the critical detection capabilities and operational ranges established by the standard for impurity analysis in benzene feedstock.
| 🎯 Parameter | 📏 Specification / Value |
|---|---|
| Applicable Benzene Purity Range | 99 % to 100 % |
| Method Detection Range (Impurities) | 2 mg/kg to 10,000 mg/kg |
| Limit of Detection (LOD) | 2 mg/kg |
| Limit of Quantitation (LOQ) | 6 mg/kg |
| Internal Standard Example | n-Octane (or other suitable known) |
| Response Factor (Non-aromatic Impurities) | 1.00 |
| Purity Calculation Basis | 100.00 % minus total impurity sum |
💡 Technical Tip: The internal standard selected (e.g., n-octane) must provide a clear, resolved peak that does not co-elute with any target impurities or the benzene solvent peak. Careful column selection and temperature program optimization are critical for achieving the defined LOD and LOQ.
⚠️ Safety and Regulatory Compliance: Users must review the specific hazard statements located in Section 7.2 and Section 8 of the standard. It is the user’s responsibility to establish safe handling practices and comply with applicable OSHA regulations, including 29 CFR 1910.1000 and 1910.1200, regarding occupational exposure limits and hazardous waste operations.
❓ Frequently Asked Questions
🔍 What is the primary application of ASTM D5713-23?
This standard is specifically used for the gas chromatographic analysis of high-purity benzene to determine its suitability as cyclohexane feedstock. It quantifies trace impurities and calculates the net benzene purity for final product inspections and process control.
💡 How is the benzene purity value derived in this method?
The purity is calculated using a summation method. The concentration of each detected impurity (calculated against an internal standard) is summed, and that total is subtracted from 100.00 %. This provides the net benzene content on a percent-by-mass basis.
📌 What are the detection and quantification limits for impurities?
The method establishes a Limit of Detection (LOD) of 2 mg/kg and a Limit of Quantitation (LOQ) of 6 mg/kg for individual impurities. The overall method is validated for quantifying impurities up to 10,000 mg/kg.
⚡ What reference standards and regulations are incorporated by reference?
The standard references several key ASTM practices, including D3437 for sampling, D6809 for quality assurance, and E29 for significant figures. It also cites OSHA regulations (29 CFR 1910.1000 and 1910.1200) for occupational safety and hazard communication compliance.