Accurate and reproducible ion mobility measurements for chemical standard evaluation

Chemical standards are used to calibrate ion mobility spectrometers (IMS) for accurate and precise identification of target compounds. Research over the past 30 years has identified several positive and negative mode compounds that have been used as IMS standards. However, the IMS research community has not come to a consensus on any chemical compound(s) for use as a reference standard. Also, the reported K(0) values for the same compound analyzed on several IMS systems can be inconsistent. In many cases, mobility has not been correlated with a mass identification of an ion. The primary goal of this work was to provide mass-identified mobility (K(0)) values for standards. The results of this work were mass-identified K(0) values for positive and negative mode IMS chemical standards. The negative mode results of this study showed that TNT is a viable negative mode reference standard. New temperature-dependent K(0) values were found by characterizing drift gas temperature and water content; several examples were found of temperature-dependent changes for the ion species of several standards. The overall recommendation of this study is that proposed IMS standards should have temperature-dependent K(0) values quoted in the literature instead of using a single K(0) value for a compound.