This page contains a Flash digital edition of a book.
The technique was capable of detecting a cotton swab spiked with 10 μg of TATP placed in a person’s pocket with a 2 second turnaround time from the person passing through the gate to the signal being detected. Being an MS technique, accuracy and sensitivity was also very good; an example where both analysis speed and accuracy have been improved in the detection of IEDs. While many of the organic peroxides

are particularly volatile, the constituents of the inorganic salt based explosives, such as the inorganic oxidising agents used, are non-volatile and as such require different analysis methods. Inorganic ion analysis has long been the domain of ion chromatography (IC), a liquid chromatographic process based on electrostatic ion-exchange (IE) interactions

demonstrated such a system which was capable of analysing both organic high explosives (using HPLC) and inorganic explosives (using IC) all in under

between analyte and column. IC is an especially stable and reliable technique with very low limits of detection and recent advances in instrumentation greatly simplifying its application. Despite recent improvements, IC still requires a relatively long analysis times. This is obviously somewhat of a limitation, especially if high throughput analysis is required. However, because it is a liquid flow- through based technique, it introduces the possibility of coupling the IC analysis to other liquid based systems such as reversed-phase liquid chromatography (HPLC) thereby allowing multiple analysis to be performed on the same sample. Tyrrell et al3

25 minutes, including re-equilibration time between each analysis. Research shows4 that analysis time can be reduced to as much as 2.6 minutes, but even that is impractical for operational deployment in a screening environment, where a few seconds analysis time is required. A relatively long analysis time is not necessarily a major issue when conducting post-blast analysis as subsequent forensic and criminal investigations can be a slow process in itself, such that the difference between a 1 minute and 20 minute analysis is not as pronounced and accuracy is a more important requirement than the absolute speed of analysis. Analysis speed is, however, of major importance when considering pre- blast analysis, especially for screening applications in high throughput areas such as airports. Capillary electrophoresis (CE) is an electrically driven separation technique that offers many advantages over the more traditional IC methods. Firstly, it uses simpler and more readily miniaturised instrumentation allowing it to be portable and easier to integrate into standalone devices. Secondly, analysis times with CE are far shorter than IC allowing a greater number of species to be analysed in a given time. Sarazin et al have demonstrated CE systems capable of analysing for anions5

and cations6

associated with inorganic IEDs. Use of a portable CE system has been shown by Hutchinson et al7

. The portable

nature of the CE instrument allowed these analyses to be performed in the field, thereby avoiding contamination and/or degradation issues associated with sample handling and delays in transporting the samples to a remote laboratory.

Improvement in the limits

of detection and speed of analysis was subsequently accomplished by changing from indirect UV detection to contactless conductivity detection within the same portable CE unit8

. While the above CE systems

The liquid explosive plot of 2006 resulted in a greater focus on liquids, aerosols and gels (LAGs) and heightened the need for technologies to be able to determine whether or not everyday products posed a threat to flights. (Credit: Green Light Ltd.)

18 Download your FREE ASI "iPad/iPhone APP" NOW

demonstrate that fast analysis for inorganic explosives is possible, the instrumentation employed is rather cumbersome with regard to sampling since samples need to be directly swabbed, extracted into a suitable extraction solution, filtered, transferred to suitable vials and then placed in the instrument. While none

February 2012 Aviationsecurityinternational

Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52