Characteristic Evaluation of Gas Chromatography with Different Detectors for Accurate Determination of Sulfur...

Sulfur hexafluoride (SF₆), which survives in the atmosphere for an extremely long period of time, is the most potent greenhouse gas regulated under the Kyoto Protocol. So, the accurate monitoring of atmospheric SF₆ plays an important role in the study of the control policies for reducing greenhouse gas emissions. The instruments for SF₆ measurement are typically calibrated using certified reference materials. The concentrations of the commercially available SF₆ reference materials usually have a broad range, from 1 μmol/mol to 6000 μmol/mol. Some characteristics including sensitivity, linear range, relative standard deviation, and accuracy are crucial for the determination of SF₆ in such a broad concentration range. Therefore, the selection of a proper detector for the accurate determination of SF₆ with such a broad range is extremely important to establish a gas chromatography (GC) method for developing SF₆ reference materials. In this paper, several typical GC methods with different detectors, including a thermal conductivity detector (TCD), a pulsed discharge helium ionization detector (PDHID), and a flame photometric detector (FPD), were carefully established for the accurate determination of SF₆ with different concentrations. The results show that an FPD detector has a relatively narrow linearity range, thus a quadratic equation should be established for building a calibration curve. The PDHID and TCD have good linearity with coefficients of 1.0000 in the concentration range of 10-100 μmol/mol (using a PDHID), and 100-1000 μmol/mol (using a TCD), respectively. Further considering the measurement errors of indication results, the PDHID is suitable for SF₆ measurement when the concentrations are below 100 μmol/mol, whereas the TCD is suitable for SF₆ measurement when the concentrations are over 100 μmol/mol. These results provide useful guidance in choosing an appropriate GC detector for the accurate determination of SF₆, which are especially very helpful for developing SF₆ reference materials.