BRINGING THE SCIENCE OF THE LABORATORY TO THE CRIME SCENEWITH NEXT GENERATION ANALYSIS TOOLS

Dr. James Wylde, Vice President – 1st Detect Corporation | David Rafferty, President and CTO – 1st Detect Corporation | Deborah Burton, Managing Director – TransGlobal Distributors BV

ACKNOWLEDGEMENTSPortions of the work presented here were funded by the US Army Defense Threat Reduction Agency - Joint Science and Technology Office and the US Army Dugway Proving Ground under Contract No. W911S6-10-C-0012. Any opinions, findings and conclusions or recommendations

expressed in this material are those of the author(s) and do not necessarily reflect the views of the DTRA JSTO or Dugway Proving Ground.

ABSTRACTBringing Science the science of the laboratory to the Crime Scene will create a Paradigm shift in the way investigationteams utilize forensic capabilities to analyze, identify and formulate results in real time. It is well known that the first 48hours after a crime is a critical period to improve the probability of solving the crime. Crucial time can be lost whilecollecting samples and transporting them to a laboratory for analysis. Also, missed evidence may only be identified afterlaboratory analysis is complete and the crime scene closed. The miniaturization and automation of traditional analyticaltechniques opens the door to faster, more accurate analysis of data outside the traditional laboratory, thus improvingthe turnaround time needed to identify forensic evidence so law enforcement can solve crimes faster. However, there isan inevitable trade off in performance with the miniaturization of laboratory analytical tools, limiting their utility forproviding the forensic quality analysis required for law enforcement. The concept of bringing the lab to the crime sceneis only achievable when lab instrumentation can be miniaturized in a way that ensures the same level of performance,accuracy and chemical detection expected from traditional lab instruments. The workhorse of traditional labs have isthe mass spectrometer; however traditional mass spectrometers require dedicated infrastructure to support a scientificlaboratory environment.

MINIATURE MASS SPECTROMETERThe instrument developed by the authors is a small (< 20 l volume, < 8 kg weight) mass spectrometer based on an iontrap architecture. In short, the instrument is capable of:

• 30 – 450 amu mass range (covering most explosives, TICs, and CWAs)• < 0.5 amu resolution (FWHM)• Sample-to-sample time: < 1 second (30 seconds with described pre-concentrator or desorber)• Power consumption: < 45 W (average) / < 65 W (maximum)• Sensitivity: < 10 ppb VOCs (< 1 ppt with pre-concentrator)

Figure 1 below shows three variants of the instruments.

Figure 1 – Photographs of 3 variants of 1st Detect miniature mass spectrometer including bench-top (left), handheld (center), and sub-component (right)

Figure 2 – representative explosives spectra showing traditional explosives PETN (top left), RDX (top center), and HMTD (top right); as well an improvised explosives UN (bottom left), AN (bottom center); and taggant EGDN (bottom right)

THERMAL DESORBERTo enable particulate and ‘sticky’ substances to cross the vacuum barrier into the mass spectrometer, a novel thermaldesorption system is being developed. The sample inlet allows collection of explosive particulate using a swipe methodsimilar to those in use today. However, to allow transfer of the vaporized explosive particulate into the vacuumchamber, the desorber is configured to evacuate the volume prior to desorption thus allowing direct injection of thesample into the instrument without the need for external ionization or ion transport (e.g., ion funnel or quadrupole ionguide).

Figure 5 – thermal desorber (left) and spectrum of HCE particulate post desorption

PURGE AND TRAPThe enable collection of threats agents from non-gaseous media, a novel purge and trap system has been developedutilizing the preconcentrator presented previously. A reduced pressure headspace is created over a liquid sample, andair bubbled through the system to release analyte. Preconcentration of the sample has been achieved with customizedadsorption matrix in a geometry optimized both for maximum adsorption collection as well as efficient high yielddesorption via direct introduction into the mass spectrometer at reduced pressure. The integrated design of thepreconcentrator with the chemical detection system is targeted at sensitive analysis of vapor samples.

Figure 4 – Photograph (left and center) of water sampler and representative data (right) showing measurement of 10 ppb benzene and chloroform in water

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PRE-CONCENTRATORA novel pre-concentrator has been designed that leverages the selective sorptive capabilities of advanced materialswith a novel design that significantly reduces the analysis time compared to currently deployed instruments. In thedesign sorbent materials are placed in a tube with a heating element. The electrical leads of the heater is connected toa power supply controlled by a computer system. Because the tube housing the sorbent is evacuated thus minimizingthe dead volume effect prior to thermal desorption, the overall concentration gain is a product of the adsorption andevacuation gains yielding a typical total gain in the range of 104. Typical analysis times are less than 30 seconds.

Figure 6 – pre-concentrator (right) and location on MMS-1000 (left)

Figure 7 – increase in sensitivity of MMS-1000 showing pre-concentration gain of ~104

Figure 9 – Repeatability performance of pre-concentrator

Figure 3 – Example of MSn (MS/MS) mode of operation

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MMS-1000 Instrument Dynamic RangePre-concentrator and Membrane Inlets (xylene)

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C5ETHYLBENZENE

Figure 8 – Separation of C3-C5 in ethylbenzene background