Accuracy of ion mobility measurements dependent on the influence of humidity

Measurements with sensor techniques in field analytical chemistry can be considerably affected by varying ambient conditions such as humidity. We systematically investigated the way in which ion mobility measurements are influenced by moisture. Both the peak positions of product ions within the spectrum and their relative abundance can vary depending on humidity. The transportation of humidity via the carrier gas into the ion mobility spectrometer causes changes in ionization pathways. Additional reactant ion species are formed and a lower relative abundance of product ions from halogenated compounds was generally observed. The peak position within the ion mobility spectrum is comparatively unaffected for the same ions. In contrast, considerable differences in drift times detected were found with increasing humidity of drift gas, while the influence on calibration was not as significant for chlorinated and brominated substances as observed for humid carrier gases.