Humidity effects on resolution and sensitivity of UV-FAIMS in VOCs detection

Abstract

Humidity is a key environmental parameter for VOCs detection technology. A study of the effects of humidity on both resolution and sensitivity of UV-FAIMS was performed at ambient temperature and pressure. This study was based on the detection and analysis of the differences in spectra (height, position and shape) and the α function of VOCs under different degrees of humidity. A total of three types of VOCs (ketones, alcohols and aromatics) were chosen as detection samples and a self-developed UV-FAIMS as a measurement instrument. The results show that sensitivity is inversely proportional to humidity for all VOCs. In addition, the resolution–humidity relationship exhibits strong dependence on the polarity of the sample ions. As relative humidity increased from 0% to 100%, the sensitivity of ketones, alcohols and aromatics was reduced by 30.9–73.0%, 40.3–64.3% and 75.1–91.6%, respectively. However, increasing humidity significantly enhanced the resolution of ketones and alcohols in the ranges of 1.82–11.82 times and 1.23–6.69 times, respectively, and hardly affected that of aromatics. Consequently, the appropriate humidity of carrier gas is of great importance in the use of UV-FAIMS.