Improvement of the ion transfer efficiency in ion mobility spectrometry-mass spectrometry

Ion Mobility Spectrometry (IMS) is a well known technique applied whenever gases need to be analyzed. Prominent examples are environmental monitoring applications, including safety related applications when handling hazardous substances in production plants (e.g. oil/gas industry) or military applications. The advantages of IMS detectors are fast response times of a few milliseconds, very high sensitivity in the ppb range and a small and simple set up that allows for portability and robustness for even field deployment. Problematic is the relatively low sensitivity, i.e. a lot of substances yield the same signal response. In order to improve, IMS are often coupled with mass spectrometry (MS) devices. The main challenge in IMS-MS is that the ions have to be transferred from atmospheric pressure on the IMS side to vacuum on the MS side, which allows only for interfaces of very small diameters and thus introduces ion loss. In this paper we have analyzed with help of finite elements method simulations how the shape of that small diameter interface influences the transmission efficiency, and improvements of over 100% could be achieved.