An Ultra-Trace Analysis Technique for SF6 Using Gas Chromatography with Negative Ion Chemical Ionization Mass...

Area of Science:

• Analytical Chemistry
• Environmental Science
• Atmospheric Chemistry

Background:

• Sulfur hexafluoride (SF6) is a highly detectable tracer gas utilized for quantifying both small and large-scale flows.
• Its high molecular electronegativity enables selective detection via negative ion chemical ionization mass spectrometry (NCI-MS).
• Efficient tracer deployments benefit from SF6's high detection sensitivity, reducing operational costs.

Purpose of the Study:

• To investigate the potential of using gas chromatography (GC) with NCI-MS for ultra-trace SF6 detection.
• To detail experimental parameters for a sensitive SF6 detection method with minimal instrument customization.
• To establish a method for detecting parts per trillion (ppt) concentrations of SF6 for underground ventilation analysis.

Main Methods:

• Utilized a Shimadzu gas chromatograph coupled with an NCI-MS system.
• Employed an Agilent J&W HP-porous layer open tubular column coated with alumina oxide (Al2O3).
• Determined the method detection limit (MDL) according to EPA guidelines.

Main Results:

• Successfully developed a method for detecting parts per trillion (ppt) level concentrations of SF6.
• The established method achieved a method detection limit (MDL) of 5.2 ppt for SF6.
• Demonstrated the efficacy of GC-NCI-MS for ultra-trace SF6 analysis in tracer gas applications.

Conclusions:

• Gas chromatography with negative ion chemical ionization mass spectrometry is a viable technique for ultra-trace SF6 detection.
• The developed method offers high sensitivity suitable for underground ventilation tracer gas analysis.
• The 5.2 ppt MDL signifies the method's capability for precise quantification of SF6 at very low concentrations.