ASTM D2427 - C2 through C5 Hydrocarbons (Gas Chromatography)
INTRODUCTION TO THE Determination of C2 through C5 Hydrocarbons in Gasolines by Gas Chromatography (ASTM D2427)
Introduction
ASTM D2427 is a critical standard that outlines the procedure for determining the presence and concentration of C2 through C5 hydrocarbons in gasoline samples using gas chromatography. This standard is pivotal for the petroleum industry, ensuring fuel quality and compliance with regulatory standards.
Scope
1.1 Objectives
This test method focuses on identifying and quantifying C2 to C5 carbon paraffins and mono-olefins in gasolines. It specifically measures the volume or mass of ethylene, ethane, propane, propylene, isobutane, n-butane, butene-1, isobutylene, trans-butene-2, cis-butene-2, isopentane, 3-methylbutene-1, n-pentane, pentene-1, 2-methylbutene-1, trans-pentene-2, cis-pentene-2, and 2-methylbutene-2.
1.2 Exclusions
Cyclic olefins, diolefins, or acetylenes are not covered under this method, as they are typically minor components in finished gasolines.
1.3 Sample Requirements
Samples should be devoid of significant material boiling lower than ethylene to ensure accurate analysis.
1.4 Units of Measurement
The standard utilizes SI units as the primary measurement system.
Referenced Documents
ASTM standards relevant to this procedure include D2001, which details the depentanization of gasoline and naphthas.
Summary of Test Method
The procedure involves injecting a sample into a gas-liquid partition column, separating components with an inert carrier gas. Components exceeding five carbon atoms are either backflushed or recorded as a broad peak, depending on the setup.
Significance and Use
Understanding the composition of light hydrocarbons in gasolines is essential for stabilizing volatile fuels and converting analyses of depentanized fractions to a total sample basis.
Apparatus and Materials
5.1 Chromatograph
A sensitive and accurate chromatograph with a thermostated oven and detection system is required.
5.2 Recorder
A recorder with a quick response time and low noise level is necessary for clear results.
5.3 Columns
The setup must include columns capable of separating and identifying individual hydrocarbons with high resolution.
Reagents and Calibration
High-purity compounds for calibration are essential. The choice of carrier gas and liquid phase must be compatible with the detection system.
Procedure
7. Preparation of Apparatus
Column preparation and chromatograph setup are detailed, ensuring optimal separation and detection conditions.
8. Test Procedure
The test involves calibration using known compounds, sample analysis through backflush or reverse flow methods, and careful handling of samples to avoid contamination.
Test Analysis
9. Data Interpretation
Comparing peak areas in the chromatogram with calibration standards allows for the quantification of hydrocarbon content.
Precision and Bias
The method includes a section on the precision of the test results and any potential biases, ensuring reliability and repeatability.
Safety and Environmental Considerations
Practitioners are reminded of the importance of safety measures and environmental practices due to the flammable nature of the samples and reagents.
Conclusion
ASTM D2427 provides a comprehensive guideline for analyzing C2 to C5 hydrocarbons in gasolines, crucial for quality control and regulatory compliance in the petroleum industry. Proper implementation ensures accurate, reliable results, contributing to the safe and efficient use of gasoline products.