Highly sensitive and selective sulfur hexafluoride detection based on DAPPI-FAIMS

Abstract

This paper proposed a novel detection method of sulfur hexafluoride (SF6) by combining dopant-assisted atmospheric pressure photoionization (DAPPI) with high-field asymmetric waveform ion mobility spectroscopy (FAIMS). Acetone was employed as a dopant to achieve high sensitivity, and the negative ion mode of FAIMS was selected to achieve high selectivity. The impact of dopant concentrations on detection sensitivity and linearity was studied, and the influence of relative humidity on the detection of sulfur hexafluoride was studied. Ammonia, benzene, and hydrogen sulfide were selected as interferences to verify the selectivity. A linearity between the concentration and the signal was studied, and the detection limit for sulfur hexafluoride was determined. Experimental results demonstrated that the DAPPI source effectively enhanced the ionization efficiency of sulfur hexafluoride with a linear coefficient of 96.1 %. The sensitivity of sulfur hexafluoride is inversely proportional to relative humidity. Sulfur hexafluoride has a characteristic fingerprint spectrum different from air background and typical interfering, and can be distinguished from interfering substances in mixtures containing ammonia, benzene, and hydrogen sulfide. The concentration of sulfur hexafluoride has excellent linearity with signal intensity, the linear coefficient was 99.8 %, and the detection limit was 0.02 ppm.