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D6142-21 – Standard Test Method Technical Guide
📐 Test Method Scope and Summary
ASTM D6142-21 provides a standardized procedure for determining known impurities in high-purity phenol using capillary gas chromatography (GC). The method is specifically intended for analyzing phenol of 99.9 % or greater purity and has been found applicable over impurity concentrations up to 70 mg/kg.
The test method involves adding a known amount of an internal standard to the phenol sample, which is then analyzed using a gas chromatograph equipped with a flame ionization detector (FID). Quantification is performed by comparing the peak areas of the target impurities against those of the internal standard, utilizing calibration standards prepared in accordance with Practice D4307.
⚙️ Analytical Procedure and Key Parameters
The analysis must be performed using a fused silica open tubular capillary column installed per Practice E1510. Sampling and handling procedures shall follow Practice D3852. Results must be rounded off in accordance with the rounding-off method of Practice E29 to determine conformance with specifications. Quality control and quality assurance measures should adhere to Guide D6809.
⚠️ Safety Precautions Required: Phenol is a hazardous chemical. Users must establish appropriate safety, health, and environmental practices. It is the responsibility of the user to consult Section 9 of the standard and OSHA regulations (29 CFR 1910.1000 and 1910.1200) for specific hazard statements and exposure limits prior to use.
📊 Method Performance and Statistical Data
Method performance was validated through an interlaboratory study conducted in accordance with Practice E691. The following table summarizes the key performance characteristics for the target impurities listed in the standard.
| 🟦 Impurity | 📏 LOD (mg/kg) | 🎯 LOQ (mg/kg) | ⚡ Application Range |
|---|---|---|---|
| Acetone | 1.7 | 5.8 | Up to 70 mg/kg |
| Acetophenone | 1.7 | 5.8 | Up to 70 mg/kg |
| α-Methylstyrene | 1.7 | 5.8 | Up to 70 mg/kg |
| 2-Methylbenzofuran | 1.7 | 5.8 | Up to 70 mg/kg |
The limit of detection (LOD) is 1.7 mg/kg and the limit of quantitation (LOQ) is 5.8 mg/kg. These values are directly calculated from the interlaboratory study data for the impurities shown above.
✅ Method Linearity: While the test method is formally validated up to 70 mg/kg, users of the standard believe the method is linear over a wider range. Laboratories extending the calibration range should verify linearity for their specific conditions and impurity profiles.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D6142-21?
ASTM D6142-21 is a standard test method for determining known organic impurities in high-purity phenol (generally 99.9 % or greater) using capillary gas chromatography with flame ionization detection (GC-FID).
💡 What are the detection and quantitation limits specified in the standard?
The method specifies a limit of detection (LOD) of 1.7 mg/kg and a limit of quantitation (LOQ) of 5.8 mg/kg. These values are based on interlaboratory study data for impurities including acetone, acetophenone, α-methylstyrene, and 2-methylbenzofuran.
⚡ What detector is specified for the gas chromatograph?
The test method specifically requires the use of a Flame Ionization Detector (FID) for the separation and quantification of target impurities.
📌 Which ASTM practices are critical for compliance with this method?
Key referenced ASTM standards include Practice D3852 (Sampling and Handling), Practice D4307 (Preparation of Liquid Blends), Practice E1510 (Column Installation), Guide D6809 (Quality Control), and Practice E691 (Interlaboratory Study Determination).