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D6387-19 – Standard Test Method Technical Guide
🧪 Overview and Scope
ASTM D6387-19 (Reapproved 2023) provides standard test methods for determining the composition of turpentine and related terpene products using capillary gas chromatography. The methods specifically quantify α-pinene, β-pinene, dipentene, terpene alcohols, and other terpene compounds. Values are reported in SI units, and users are responsible for establishing safety and health practices. This standard was developed in accordance with international principles on standardization.
⚙️ Test Method and Procedure
The test procedure involves preparing a weighed mixture of the sample with an internal standard, followed by injection into a temperature-programmable capillary gas chromatograph. The chromatogram is analyzed for peak areas of target compounds and the internal standard. Results are calculated using calibration factors and weight ratios.
Two quantification methods are defined:
- Internal Standard Method: Provides absolute concentration values by comparing peak areas of compound to internal standard.
- Area Percent Method: Offers relative concentrations based on peak area percentages, ideal for hydrocarbons with similar response factors.
A polar or nonpolar capillary column may be used depending on the separation requirements of the compounds under analysis.
| 🟦 Method | 📏 Quantification Type | 🎯 Ideal Use Case | ⚡ Precision Characteristic |
|---|---|---|---|
| Internal Standard | Absolute values | High accuracy required | Excellent repeatability |
| Area Percent | Relative values | Routine screening | Moderate reproducibility |
📊 Precision and Reference Data
According to the standard, the test method delivers excellent repeatability within a single laboratory but only moderate reproducibility across laboratories. This differential is attributed to the variety of GC columns and operating variables used by different workers. Close definition of GC conditions is essential for reliable inter-laboratory comparisons.
⚠️ Note: The standard emphasizes that when comparing results from different laboratories, it is critical to define GC operating conditions closely to minimize variability.
Related standards referenced include D13 (Spirits of Turpentine), D801 (Dipentene), D802 (Pine Oils), D804 (Terminology), and E691 (Precision Practices). These provide additional context and testing procedures.
❓ Frequently Asked Questions
🔍 What terpene compounds are determined by this standard?
The standard covers α-pinene, β-pinene, dipentene, terpene alcohols, and other terpene components in turpentine and related products.
💡 What is the difference between the two quantification methods?
The internal standard method yields absolute concentration values, while the area percent method provides relative concentrations. The former requires calibration factors, while the latter is simpler for hydrocarbon analysis.
⚡ Why is reproducibility only moderate in this test method?
The variability in GC columns and other operational parameters among participants contributes to greater than normal differentials in reproducibility, as explained in the standard.
📌 What units are specified for reporting results?
SI units are required by the standard to ensure uniformity in reporting and interpretation of results.