Accurate Evaluation of Potential Calibration Standards for Ion Mobility Spectrometry

Ion mobility spectrometry (IMS)-based instruments have historically been accurate to, at best, ±2% of the reduced ion mobility (K₀) value of the chemical of interest. Fielded IMS-based detectors that are in use for hazardous and illicit substance detection are subject to false-positive alarms because of this inaccuracy and the resulting wide alarm windows, which are required to maintain a high rate of true-positive alarms. To reduce false-positive alarm rates and improve the accuracy of any IMS-based instrument, accurate K₀ values of an ion mobility reference standard need to be used for ion mobility scale calibration. However, a suitable calibrant has yet to be accurately analyzed and agreed upon by the IMS community. In this study, we have chosen five potential IMS calibrants on the basis of their rating against seven criteria for suitable standards and analyzed them as a function of drift gas temperature and humidity using an accurate ion mobility instrument. Recommendations are made herein for each potential calibrant's suitability as a standard for the wider IMS community.