High Accuracy Ion Mobility Spectrometry for Instrument Calibration

Ion mobility spectrometry (IMS) is widely used to characterize compounds of interest (COIs) based on their reduced mobility ( K₀) values. In an attempt to increase the accuracy and agreement of studies, the most recommended method has been to use a reference compound with a known K₀ value to calibrate the instrument and calculate COI K₀ values from normalized spectra. Researchers are limited by the accuracy of previous K₀ value reference measurements on which to base their calibrations. Any inaccuracy in these reference K₀ values, typically ±2%, will propagate through to the calculated K₀ value of the COI. For this reason, there is a need to standardize reference K₀ values with improved accuracy. Through improvement of the accuracy of reference measurements, a lower degree of error will propagate through new K₀ value calculations. The K₀ values of the ammonium reactant ion, the potential reference standard dimethyl methylphosphonate (DMMP), and three explosive COIs were characterized at multiple drift gas temperatures, drift gas water contents, and electric field strengths on an accurate ion mobility spectrometry instrument. K₀ values reported here are known to ±0.1% as a result of reducing the error of all instrumental parameters.