Analysis of Insulation Gas SF6 by the GC-BID System

Significance of the Topic

Sulfur hexafluoride (SF6) is widely used in electrical equipment as an insulation and tracer gas because of its exceptional chemical stability and dielectric properties. However it is also one of the most potent greenhouse gases regulated by international agreements such as the Kyoto Protocol. Reliable analysis of SF6 and its impurities is critical for leak detection, quality control of insulating gas, and verification of gas recovery processes.

Objectives and Study Overview

This application note demonstrates the capability of a Shimadzu Tracera gas chromatograph equipped with a barrier ionization discharge detector (BID) for sensitive quantitation of SF6 in ambient air and simultaneous analysis of trace impurities in high-purity SF6. Key goals include achieving low detection limits, broad linear dynamic range, and accurate quantitation without requiring radioisotope detectors.

Methodology and Instrumentation

The study employed two analytical protocols:

• Trace SF6 in air was analyzed using an Rt-Msieve 5A capillary column (0.53 mm × 30 m, 50 μm film) with split injection. Temperature programming from 35 °C to 270 °C enabled separation of SF6 from oxygen and hydrogen. Helium served as carrier gas at constant linear velocity.
• Impurities in bulk SF6 were separated on a micropacked ST column (1 mm × 2 m) under pressure-ramped conditions. A split ratio of 1:4 and a temperature gradient up to 265 °C allowed baseline separation of inorganic gases and light hydrocarbons despite a large SF6 matrix peak.

Instrumentation Used

• Gas chromatograph: Shimadzu Tracera (GC-2010 Plus with BID-2010 Plus)
• Injection port unit: SPLITTER INJ for trace gas analysis
• Gas sampler: MGS-2010
• Data system: LabSolutions LC/GC software

Main Results and Discussion

• Detection limit for SF6 in air reached 0.1 ppm with a signal-to-noise ratio of 24. Calibration was linear from 0.1 to 50 ppm (R2=0.9998) supporting reliable quantitation over four orders of magnitude.
• Simultaneous analysis of impurities in high-purity SF6 achieved detection of hydrogen, methane, carbon monoxide, carbon dioxide, nitrous oxide, acetylene, ethylene, propylene, and propane at levels between 0.9 and 21 ppm. No adverse impact from the dominant SF6 matrix peak was observed.

Benefits and Practical Applications

This GC-BID approach offers high sensitivity without requiring radioactive detectors, simplifies workflow, and ensures accurate analysis at trace and bulk concentrations. It supports leak monitoring, verification of recovered gas purity, and routine quality control in utilities and manufacturing environments.

Future Trends and Potential Applications

Advances may include field-deployable micro-GC-BID systems for on-site monitoring, integration with automated samplers for continuous emission surveillance, and expanded multicomponent analysis for environmental and industrial gas streams. Coupling with data analytics could further improve greenhouse gas management.

Conclusion

The Shimadzu Tracera GC with BID detector delivers robust, sensitive, and accurate analysis of SF6 and its impurities. Its broad dynamic range and non-radioactive detection make it a versatile tool for environmental monitoring, equipment maintenance, and quality assurance in the electrical industry.