Sulfur Analyzer Nexis GC-2030PFPD3 GC-2014PFPD3

Significance of the Topic

The determination of sulfide compounds in liquefied petroleum gas and liquefied natural gas is critical for safety, regulatory compliance, catalyst protection and fuel quality control. Accurate sulfur speciation ensures the prevention of corrosion, minimizes environmental emissions and supports industrial process optimization.

Objectives and Study Overview

This application note describes a gas chromatographic method employing a pulsed flame photometric detector coupled with dual capillary columns to separate and quantify trace sulfur compounds in LPG and LNG. The approach is designed to meet the requirements of the ASTM D6228 standard and to provide robust detection across a wide concentration range.

Methodology and Instrumentation

A vaporized sample stream is split into two sulfinert sample loops and injected simultaneously onto a polar Gas-Pro column and a non-polar Rtx-1 column. These columns address individual separation challenges such as H2S absorption and COS coelution. The column effluents are recombined and analyzed by a pulsed flame photometric detector, producing an equimolar sulfur response. Calibration is performed using either standard sulfur gas mixtures or a permeation source. Key instrumentation includes:

• Nexis GC-2030PFPD3 or GC-2014PFPD3 gas chromatograph
• PFPD detector optimized for sulfur selectivity
• Sulfinert 6-port valve for automated sample switching
• Vaporizer device for LPG/LNG sample vaporization
• Lab Solutions GC workstation software for data acquisition and processing

Main Results and Discussion

The dual-column configuration achieves baseline separation of eight sulfur analytes including hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, dimethyl sulfide, carbon disulfide, propyl mercaptan and butyl mercaptan. Detection limits down to 50 parts per billion and a working range from 0.05 to 100 ppmV were demonstrated. Representative chromatograms show clear elution profiles without coelution artifacts, confirming the method’s capability to resolve challenging sulfur species in a single analysis.

Benefits and Practical Applications

This method offers high selectivity for sulfur, reduced adsorption losses thanks to inert sample lines, and simplified quantification through equimolar detector response. It supports both routine quality control in petrochemical laboratories and compliance testing under ASTM D6228. The ability to analyze multiple sulfur compounds in one run increases laboratory efficiency and lowers operational costs.

Future Trends and Applications

Ongoing developments may include coupling to mass spectrometry for confirmatory identification, miniaturized or portable GC systems for field monitoring, improvements in detector technology for lower detection limits, and expanded use in biofuel and renewable gas analyses. Real-time online monitoring solutions are also a growing area of interest.

Conclusion

The dual-column PFPD method provides a robust, sensitive and accurate approach for comprehensive sulfur speciation in LPG and LNG. Its compliance with ASTM D6228 and its operational advantages make it a valuable tool for industrial laboratories focused on fuel quality, safety and regulatory compliance.

Reference

• ASTM D6228 Standard Test Method for Sulfur Compounds in Natural Gas by Gas Chromatography