Oxygen enhanced plasma discharge and its application as carrier gas for high-field asymmetric ion mobility spectroscopy.

This paper explores the application of a helium-oxygen mixture in gas curtain plasma ion source (GCP)-high-field asymmetric ion mobility spectroscopy (FAIMS). A gas mixture of oxygen and helium gases has been employed as the discharge gas. The experiments were conducted using 2-butanone, acetone, methanol, and ethanol as the sample under a radio frequency field strength of 20.3 kV/cm. When the flow rate of the discharge gas is fixed at 0.8 L/min and the helium oxygen mixture ratio is fixed at 7:1, the maximum ion signal can be obtained. With the flow rate of the carrier gas fixed at 1.2 L/min, using 100% oxygen as the carrier gas resulted in a 2.85-fold increase in signal intensity and a 72.67-fold improvement in resolution compared to a mixture of oxygen and nitrogen, as well as 100% nitrogen. Therefore, adding oxygen can not only improve the detection sensitivity of FAIMS, but also enhance its resolution.