Determination of Oxygenates in C2, C3, C4 and C5 hydrocarbon Matrices according ASTM D7423-09 using

Significance of the Topic

The accurate measurement of trace oxygenates in light hydrocarbon streams is critical to maintaining catalyst performance in downstream polymerization and fuel blending operations. Even low ppm levels of alcohols, ethers, aldehydes and ketones can adversely affect catalyst activity and product quality. Implementing a reliable, sensitive and fast analytical method supports both process optimization and regulatory compliance.

Objectives and Study Overview

This application note describes the implementation and validation of ASTM D7423-09 for the quantification of oxygenates in C2–C5 hydrocarbon matrices. Using the AC Oxytracer GC system with Deans switch technology, the goal is to achieve baseline separation, high sensitivity and robust repeatability within a total analysis time under 30 minutes.

Methodology and Instrumentation

The system is configured as follows:

• Gas chromatograph with split/splitless inlet
• Automatic Liquid Sampler plus Gas Sampling Valve and Liquid Sampling Valve
• Pre-separation column and analysis column in a temperature-programmed oven
• Deans switch to divert bulk hydrocarbon matrix away from the analysis column
• Flame ionization detector(s) for quantitation
• Electronic pressure and flow control on all gas lines

Calibration is performed externally using dedicated liquid standards covering 0.50–100 mg/kg. Retention times and detector response factors are established for 20+ oxygenate compounds.

Main Results and Discussion

Validation metrics demonstrate that the AC Oxytracer meets and surpasses method requirements:

• Separation efficiency: Complete resolution of key ether peaks (ETBE, MTBE, DIPE) and individual aldehydes for accurate integration
• Retention time repeatability: RSD <0.05 % over ten consecutive injections
• Area repeatability: RSD ≤0.3 % for LSV and ≤2 % for GSV introductions
• Linearity: Correlation coefficients >0.999 across a five-point calibration (5–100 ppm)
• Detection limits: Typically 0.01–0.1 ppm, depending on compound and injection mode

Benefits and Practical Applications

The described method offers:

• Rapid cycle time <30 minutes for high sample throughput
• No matrix interference due to Deans switch venting of bulk hydrocarbons
• Robust performance with FID stability and inert flow paths
• Comprehensive coverage of alcohols, ethers, aldehydes and ketones in light hydrocarbon feeds

Future Trends and Potential Applications

Looking ahead, potential developments include coupling the Deans switch approach with mass spectrometric detection for enhanced selectivity, expanding the method to heavier hydrocarbon fractions, integrating real-time process monitoring and applying advanced data analytics for predictive quality control. Miniaturized GC platforms and greener carrier gas alternatives may further streamline routine deployment in industrial labs.

Conclusion

The AC Oxytracer system, using ASTM D7423-09, delivers fast, sensitive and reproducible analysis of trace oxygenates in C2–C5 matrices. Its robust design and superior chromatographic performance enable reliable quantitation at low ppm levels, supporting downstream processing and quality assurance in petrochemical and fuel industries.

References

• ASTM D7423-09: Standard Test Method for Determination of Oxygenates in C2–C5 Hydrocarbon Matrices by Gas Chromatography