Griffin 824 Operational Suitability: Evaluation of Clear-Down Time for Mass Spectrometry- Based Trace Detector WHITE PAPER. Philip J. Tackett, Ph.D.

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1 WHITE PAPER Griffin 824 Operational Suitability: Evaluation of Clear-Down Time for Mass Spectrometry- Based Trace Detector INTRODUCTION Philip J. Tackett, Ph.D. 1

2 SYNOPSIS The following white paper describes the current approach to checkpoint screening for explosives and narcotics using Ion Mobility Spectrometry (IMS) instruments and contrasts it with a state-of-the-art Mass Spectrometry (MS) instrument, the Griffin 824. Both instruments are intended for use as trace detectors in checkpoint applications and offer similar concepts of operation (CONOPs). False alarms, required maintenance, and length of clear-down times all lead to instrument down time and can ultimately affect the speed of checkpoint throughput. Tests were conducted to compare a key performance metric, instrument clear-down, which is the time required for a system to become operable following an alarm. The ability of a trace detector to quickly and accurately complete a clear-down process is important for one main reason: Trace detection systems are only effective when operational. This paper will show that the Griffin 824 MS-based system demonstrated a clear-down time reduction of 98.7% (10 seconds vs. 13 minutes) for TNT 1 and 94.4% (10 seconds vs. 3 minutes) for Heroin 2 when compared to the IMS-based system. INTRODUCTION & TECHNOLOGY OVERVIEW Efficient throughput is critical for security checkpoints in a broad range of applications, from visitor screening for public transit, correctional facilities, and event venues, to mail and cargo screening for military, public and other private institutions. Items encountered in a checkpoint must be thoroughly and quickly screened for trace levels (very small amounts) of target materials that can indicate illicit activity. Checkpoint operators collect these trace residues by wiping personal belongings, parcels, cargo, and other surfaces with a sample ticket. The ticket is then inserted into a detection system that performs rapid analysis. The reality is that items encountered in a checkpoint often contain nontrace amounts of materials that plague existing IMS-technology and ultimately slows down checkpoint throughput. IMS-based trace detectors are often rendered temporarily inoperable at checkpoints. This is due to the inherent design of IMS, which relies on recycling a constant flow of gas throughout the sample path of the instrument. Materials encountered by IMS-based instruments are thermally desorbed and enter the vapor phase. This vapor is then transferred into the carrier gas and into the drift tube region of the system for analysis, which all the while must remain free of water vapor and contamination 3. In order to keep 1 TNT is an abbreviation for the chemical compound 2,4,6-Trinitrotoluene, one of the most commonly used explosives for military and industrial applications. 2 Heroin is a drug often used for illicit recreational use. 3 Bellerby et al., IJIMS

3 the IMS clean and dry, regularly scheduled maintenance procedures are performed during which time the system is not available for screening operations. When a non-trace amount of material enters the IMS, only a fraction of the vapor is used for analysis and a significant portion is retained within the carrier gas being recycled throughout the instrument. The presence of this remaining vapor often causes the instrument to detect target materials on subsequent clean samples, which causes false alarm conditions. False alarms require clear-down procedures to be initiated, as well as secondary screening protocols to confirm the alarm. IMS-based instruments are also subject to false alarms from non-target materials (materials other than explosives and narcotics). Clear-down and secondary screening is also required in these instances. After all alarms (whether false as those described previously or true where a threat is actually present), IMS-based detectors require the operator to insert clean sample tickets until no remaining alarms are encountered. Depending on the amount of material encountered, this clear-down process can be time consuming. Field operators have suggested that clear-down can take minutes to hours to complete when an IMS encounters non-trace amounts of material. Until the clear-down process is complete, the detector is not operational. Even further, the consumables used in the clear-down process add cost to daily operations. FLIR Systems has developed a solution to this operational challenge with the Griffin 824 trace detection mass spectrometer system (Figure 1). Mass Spectrometry is a widely trusted technique used for definitive chemical analysis. Its inherent ability to provide selective chemical identification in operational environments is unmatched by IMS technology, offering 10x greater capacity to differentiate between non-target and target materials 4. The Griffin 824 was also designed to maximize Figure 1. Griffin 824 Trace Detection MS system operational time by incorporating an open loop that does not recycle air inside the system. Rather than recycling carrier gas continuously within the instrument, the Griffin 824 directly draws a sample from the sample ticket under vacuum from the thermal desorber and into the mass analyzer. No carrier gas or cleaners are required, which minimizes consumable costs. Any remaining vapor-phase target material is contained within the thermal desorber subsystem, which undergoes a robust yet rapid flush stage at the conclusion of each sample analysis. During this automated process, the thermal desorber is flushed with clean air by a factor or more than 100x. This greatly 4 Committee on Assessment of Security Technologies for Transportation, National Research Council of the National Academies. The National Academies Press: Washington, D.C.,

4 reduces carry-over of non-trace amounts of material from sample-to-sample and further decreases the probability of false alarms in subsequent analyses. In most cases, carryover is limited to a single subsequent analysis or eliminated altogether, significantly increasing instrument uptime and ultimately checkpoint throughput. INSTRUMENTATION The following trace detection instruments were used to complete an experiment that compares clear-down time, a key performance metric for checkpoint security. Mass Spectrometer (MS) Griffin 824 Ion Mobility Spectrometer (IMS) Representative competitor system EXPERIMENTAL A non-trace mass loading of target material was dosed onto a portion of transfer material and allowed to dry. An OEM 5 sample ticket was obtained for each of the two tested instruments (Figure 2) and the transfer surface was swiped. The sample tickets were inserted into the respective trace detection instruments and analyzed. Following analysis and acceptance of the resulting alarm condition, a new, clean sample ticket was immediately analyzed. The results of this sample ticket were recorded (alarm/no alarm), and new, clean sample tickets were repeatedly analyzed until the alarm condition was no longer encountered and a sample passed condition was met. This procedure was performed three times for two separate targets: TNT (explosive) and Heroin (narcotic). A B Figure 2. OEM sample tickets: A) IMS-ticket; B) MS-ticket RESULTS & DISCUSSION Figure 3 shows the average clear-down times for TNT and Heroin when introduced to the MS-system and IMS-system. The clear-down time was approximately 13 minutes for TNT and 3 minutes for heroin when utilizing the IMS-system (as indicated in bright red, Figure 3). However, given the same mass loading for each target, the MS-system (Griffin 824) displayed an average clear-down time of 0.16 minutes (10 seconds) for both TNT and heroin (as indicated in black, Figure 3). 5 Original Equipment Manufacturer 4

5 20 MS-Based Griffin 824 TD-MS System, G824 IMS-Based IMS-based trace System detector Clear-down time (minutes) min 13 min 0.16 min 3 min 0 TNT Heroin Figure 3. Experimentally determined clear-down times associated with Griffin 824 as compared to traditional IMS-based trace detection These data points suggest that the MS-based Griffin 824 was available for use after one clear-down analysis was performed. The IMS-based system required ten to forty cleardown analyses, during which it was unavailable for additional screening purposes. This demonstrates a substantial increase in system uptime for the Griffin 824 using MSbased technology over existing IMS-based technology. SUMMARY False alarms, required maintenance, and length of clear-down times all lead to instrument down time that negatively impact the speed of checkpoint throughput. All trace detection systems require some amount of clear-down time, which makes it a critical performance metric for checkpoint applications. Offering up to a 98.7% decrease in clear-down time over IMS, the Griffin 824 provides the opportunity for significantly increased throughput in checkpoint applications. Without adding any complexity to the existing protocols, security officials are provided with accurate and reliable information that leads to quick, intelligence-based decision making. Innovative FLIR mass spectrometry trace detection and analysis instruments like the Griffin 824 are ready to replace out-of-date IMS instruments for explosives and narcotics screening in checkpoints. 5

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