ABSTRACT

Ion mobility spectrometry (IMS) has been used for a wide variety of analytical applications, ranging from applications related to forensic chemistry to security checkpoint screening and detection for small molecules.(1) More recently ion mobility-mass spectrometry (IM-MS) has emerged as an analytical technique for the characterization of petroleum crude fractions,(2) biophysical studies of biological molecules,(3) studies of protein complexes,(4) and studies of protein aggregation related to diseases such as Alzheimer’s and Parkinson’s diseases and diabetes.(5) Although IMS has changed very little since it began to emerge as an analytical technique in the 1970s,(6,7) the coupling of IMS with modern high-performance mass spectrometers equipped with electrospray ionization (ESI) and/or matrix-assisted laser desorption ionization (MALDI) sources has catalyzed new developments and applications of the technique. In addition, the growing numbers of problems now being addressed by using IM-MS has spawned new technological developments.(8) Although IMS was first combined with orthogonal time-of-flight mass spectrometry (TOFMS) instruments more than 40 years ago,(9) over the past decade there has been tremendous growth in IMS-TOFMS instrumentation. As the complexity of chemical

6.1 Introduction .................................................................................................. 137 6.2 The Variable-Temperature IM-MS Instrument Design ................................ 142 6.3 Experimental Results .................................................................................... 145 6.4 Conclusions ................................................................................................... 149 References .............................................................................................................. 149

problems being addressed by IMS has increased, the demand for higher resolution IMS techniques has also increased. As is typical in the field of technology development, researchers have attempted a variety of avenues to increase the resolution of IMS, such as increasing the pressure of the drift gas,(10) decreasing the temperature of the drift gas,(11,12) increasing the length of the IMS drift tube,(13,14) and seeking alternatives to uniform drift field IMS experiments.(15,16) This chapter focuses primarily on studies aimed at developing variable-temperature (VT)IMS with the goal of using low temperature to increase the resolution for the drift tube ion mobility method.