Fundamentals, Development and Applications of Ion Mobility Spectrometry (IMS) for Enhanced Trace Detection of Threat Agents

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The globalisation of our society means that there is an ever-increasing need, within homeland security, for reliable, real-time and sensitive detection of a wide range of substances that are a threat to our society. The chemicals to be detected range from explosives, through to illicit narcotics and chemical and biological agents. The ability to quickly and accurately measure these hazardous compounds, and distinguish them from a complex chemical environment, is vital to our nation's needs for its fight against crime and terrorism.Commonly used equipments for this type of security are often based on Ion Mobility Spectrometry (IMS), and which are often employed to screen people or objects. You may have experienced its application at airports if you had your laptop checked for traces of explosives, or if you walked through a Sentinel , used to screen people for trace amounts of explosives or narcotics. IMS is however, not only employed in transportation security, but also in military and civilian facilities.IMS operates by creating charged molecules (ions), which can either be positively or negatively charged. These ions migrate under the influence of an electric field with a mean constant velocity and collide with neutral molecules. Collisions and reactions (ion-molecule reactions) lead to the formation of other ionic species which may react with a trace gas. Changes in the resultant mobility of ions as they progress along an electric field are monitored and processed to try to identify any threat materials present.The IMS systems currently deployed have a number of limitations, including sensitivity and selectivity, which result in the technology not being fully exploited. The major limitation is low chemical specificity, restricting the type of compounds which can be readily detected. Many explosives and chemical threats just can not be detected. To overcome this requires a novel scientific approach, employing a detailed fundamental and phased research programme to understand the key chemical processes employed in IMS, and in particular to those occuring in the latest generation of drift tube systems being developed by Smiths Detection Ltd, Watford, UK. A systematic study is required which will investigate the ionization chemistry, the use of chemical dopants (to change the chemistry), and mode of operation (negative or positive ion mode, high or low electric field). An Ion Trap Mass Spectrometer (ITMS), coupled to novel IMS systems, will be the main device employed to study the complex ion chemistry. One of the advantages of the ITMS is that structural information on the ions can be obtained. By utilizing and tailoring the ion chemistry it will be possible to refine, extend, and enhance the operation of IMS. Together with lead scientists and engineers working in the world's largest company which manufactures, develops and markets IMS systems, the UK based company Smiths Detection Ltd (website address: www.smithsdetection.com and http://trace.smithsdetection.com/), we will pursue a four year programme of research to achieve the above objectives. Through Smiths Detection Ltd, this should lead to the development of a unique instrument, increasing the dimensionality of current IMS systems, ultimately leading to a new generation of chemical detectors to be deployed to fight crime and terrorism and increase security within the UK.