Vehicle-Mounted Portable Mass Spectrometry System for the Covert

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Vehicle-Mounted Portable Mass Spectrometry System for the Covert Detection via Spatial Analysis of Clandestine Methamphetamine Laboratories Phillip M. Mach,†,§ Ethan M. McBride,†,§ Zachary J. Sasiene,† Katie R. Brigance,† Shelia K. Kennard,† Kenneth C. Wright,‡ and Guido F. Verbeck*,† †

Department of Chemistry, University of North Texas, Denton, Texas 76203, United States Inficon, Syracuse, New York 13057, United States

‡

ABSTRACT: The ability to detect atmospheric effluent from clandestine methamphetamine manufacture is a useful tool for law enforcement. A membrane inlet mass spectrometer is mounted onto an all-electric drive capable hybrid vehicle that samples the atmosphere while in motion. Attributing a latitude and longitude to each spectrum collected, unique chemical fingerprints from clandestine manufacture are then mapped. This location-based mass spectrum data provides a localization to an area of interest. The synthesis of methamphetamine precursors was performed, and the impurities from such reactions were observed. A mock manufacture was setup, and the impurities were introduced into the atmosphere via heating. The detection of products and impurities using this mobile platform has shown the effectiveness of locating and localizing the manufacture of methamphetamine.

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ATS synthesis, including 1-phenylpropan-2-one (or P2P), from which forensics have been able to determine the routes of synthesis from apprehended samples.11 Biological systems, most commonly baker’s yeast, have been used to yield 12 L-phenylacetylcarbinol, a precursor to methamphetamine. The genesis of using yeast results from the restricted availability of ephedrine and pseudoephedrine, indicating a heightened awareness of clandestine chemists to advances in the literature. Chemometric procedures have been developed that consider ratios of impurity concentration and isotopic distributions.13 Methods of manufacture and precursor synthesis have been well studied and ultimately result in abilities to trace end point products to these individual routes and reagents. Environmentally, these manufacturing methods often emit trace chemicals that are detectable on surfaces and in the atmosphere14 but are often unregulated.15 Various scenarios have been constructed to mimic environments where instrumentation can be used for on-site testing. Importation of cocaine in cargo containers through the port of Miami has provided a test situation for high volume vapor sampling with analytical methods such as ion mobility spectrometry (IMS) and gas chromatography mass spectrometry (GC/MS) providing drug identification.16,17 IMS of illegal drugs using varying temperature and concentration parameters has also been conducted in

lobal manufacture of amphetamine-type stimulants (ATS) has risen over the past decade, and the amount of global seizures of methamphetamine has risen 158% over the past five years, up to 88 tons in 2013.1 In 2014, there were almost 3 tons of methamphetamine seized in the United States alone by the DEA.2 Further complicating law enforcement efforts, methamphetamine production is possible in a myriad of locations including suburbs, trailer parks, apartments, hotels, and mobile laboratories. A search area cannot therefore be minimized based upon a specific infrastructure. Currently, law enforcement requires a broad spectrum of methods to locate such covert activities, including trained canines, undercover agents, and extensive logistical support. Presented here is the development and application of a vehicle-based mobile mass spectrometer for the detection of the precursors and synthetic byproducts of methamphetamine by atmospheric spatial analysis that can help supplement these current law enforcement techniques with a powerful, mobile system. Illicit drug seizures are often subject to forensic analysis confirming or denying the presence of illegal ATS. Beyond confirmation of the presence of a scheduled chemical, efforts to profile the impurities present in these samples results in chemical identifiers of synthetic routes.3,4 A myriad of routes (Leuckart, reductive amination, etc.) have been used to synthesize ATS, and each method has unique precursors and impurities that can help identify the route of manufacture.5−9 Common ephedrine-based methods have also been analyzed with three different routes studied.10 Further analytical methods have been applied to the synthesis of precursor chemicals in © 2015 American Chemical Society

Received: August 25, 2015 Accepted: October 12, 2015 Published: October 12, 2015 11501

DOI: 10.1021/acs.analchem.5b03269 Anal. Chem. 2015, 87, 11501−11508

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Analytical Chemistry

Figure 1. Reaction mechanism for the production of phenylpropanone (P2P).

Figure 2. Mobile system replacing the front passenger seat. The unit is placed in a rack mountable case. The inset shows the quarter glass replacement inlet. 11502

DOI: 10.1021/acs.analchem.5b03269 Anal. Chem. 2015, 87, 11501−11508

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Figure 3. (A) Reaction mechanism for the production of dibenzylketone (DBK). (B) Baseline mass spectrometric data. (C) Obtained data resulting from displacement of DBK during mock manufacture.

customs situations.18 This resulted in determination of suitable analysis conditions for amphetamine and lysergic acid diethylamide (LSD) at nanogram concentrations.18 Other studies have analyzed surface chemistry of contraband via IMS.19 Development of additional techniques includes fieldable sensors and instrumentation. The U.S. Drug Enforcement Agency (DEA) has collated efforts for the detection of drugs of forensic interest.20 Even solvents, such as pyridine from the Leuckart synthetic method, have been focused on as a detectable material and subsequent rapid methods have been developed with IMS and photoionization for their detection.21 Field-deployable systems have been used in clandestine lab sites and have been utilized in forensic processing of the scene.22,23 Biosensors and immunosensors have been developed to detect the presence of illegal drugs and even explosive chemicals.24−28 Further overviews specifically toward IMS29−32 and other detection technologies have been well documented.33 Ultimately, clandestine manufacture provides two means of direct evidence given that there are lasting environmental signatures within the area of synthesis and continual effluent during the various stages of production. Efforts to quantify environmental impacts have resulted in the creation of health and safety policies to use in clandestine lab reclamation.15,34 These proposed strategies apply specifically to remediation of contaminated infrastructure. Analysis in soil samples shows effects of manufacture exist outside the clandestine laboratory itself,35

Figure 4. Representative scan obtained during operation of the vehicle. Analyses performed yield hundreds of similar spectra. Constituents of the mock synthesis yielded solvent peaks and those associated with fragmentation from the target precursors and impurities.

often as a result of improper disposal of chemicals. Ongoing methods are being developed for real time sampling and monitoring of chemical reactions involved in the manufacture process of illegal drugs, including utilization of solid phase microextraction (SPME) in capturing drug vapors.36 SPME fibers proved effective in observations of decomposition and 11503

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The Dakin−West reaction was originally developed to convert α-amino acids into their respective α-acetylamino-alkyl methyl ketones38,39 but works for certain nonamino acids.40 This reaction mechanism, shown in Figure 1, involves the interconversion of phenylacetic acid to its anhydride in the presence of acetic anhydride. This phenylacetic anhydride loses a proton in the presence of pyridine. It is then acylated by another acetic anhydride and subsequently deacylated to produce a β-keto acid and finally decarboxylated to produce the final ketone product. After the reaction was complete, the reaction mixture was then subjected to analysis within the reaction vessel without further alterations or additions. For the prevention of information on clandestine synthesis becoming publically available, only general details on the synthetic procedure will be given herein. All end point products were then classified with GC/MS (Focus GC/Polaris Q) to confirm the presence of the target precursor and expected byproducts. Phenylacetic acid was combined with pyridine and acetic anhydride and refluxed under anhydrous conditions for a period of time. Pyridine, P2P, and acetic anhydride are all flammable liquids and as such must be kept away from any sources of ignition during the reaction process and stored in an appropriate flammable liquids cabinet. Acetic anhydride can also react violently with water, so storage and handling must preclude its exposure to sources of water. Mock Clandestine Lab Manufacture. For simulating the environment of a methamphetamine synthesis, a mobile home trailer park was used. Located near campus and referred to as Crime Scene City, it is used by forensic science students. Multiple unoccupied mobile homes are in close proximity to one another, simulating a common environment where a “cook” could take place. The location is easily accessible, and readings can be taken with the mobile instrumentation in all directions directly adjacent to the site. Within the mobile home, the reaction mixture was placed in a bathroom on a hot plate with a stir bar and heated to temperatures consistent with a methamphetamine reaction. Windows and vents in the bathroom were opened to allow effluent to escape. PPE was equipped at all times within the mobile home and directly adjacent to the site to prevent the inhalation of any effluent vapors or accidental exposure via skin contact. Instrumentation. The mass spectrometer is a Transpector MPH (Inficon, Syracuse, NY) Residual Gas Analyzer (RGA). The unit is contained in a ruggedized rack-mountable case. The membrane inlet front end was designed on a 2.75″ Conflat blank flange with feedthroughs that provide mountings for the tubular membrane (Helixmark, Carpinteria, CA). The system is mounted where the front seat existed in a Ford Fusion Energi, Figure 2. The Fusion offered hybrid drive with the ability to override traditional gasoline engine function. This removed any combustion interferences while mapping an area. Atmosphere is introduced into the system through an in-house made quarter glass replacement, providing an inlet in which a diaphragm pump continuously pumps through atmosphere. From the atmospheric sampling tube, a smaller diaphragm pump samples a small quantity of air to pass through the tubular membrane. The system repeatedly scans masses and tags each scan with an associated latitude and longitude, using the combination of a Python script and Arduino-based microcontroller with GPS capability. Post-processing of data uses Google Earth to plot obtained intensities for a given mass. Colored circles attribute a location and intensity in a user-friendly format. These masses are associated with given byproducts of synthesis and further

Figure 5. (A) Mass spectra of product P2P. (B) The precursor phenylacetic acid.

reaction products. Syntheses of methamphetamine via two clandestine methods were monitored with ambient ionization methods in real time with portable mass spectrometry.37 Their results found that covert synthesis was identifiable throughout the reactions by the effluent produced. Because clandestine manufacture of ATS is typically accompanied by unavoidable byproducts, reactions often exude many chemical signatures. The following work catalogs the development of detection methods of clandestine laboratories using an all-electric capable hybrid vehicle-mounted mass spectrometer. The system uses a custom atmospheric intake that continually samples and passes samples through a membrane inlet. Membrane inlet mass spectrometry (MIMS) uses a semipermeable membrane to allow analytes to pass through for analysis while maintaining vacuum of the system. Obtained mass spectra are then GPS tagged to locations. A mock covert methamphetamine synthesis was performed, producing effluent that was subsequently detected for the presence of precursors and byproducts. The vehicle then mapped the area and data was plotted so that spatial analysis could be performed. Ultimately, the system detected the atmospheric constituents that constitute ongoing methamphetamine manufacture.

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EXPERIMENTAL SECTION Synthesis. For analysis of the precursors and impurities commonly found in the synthesis of an ATS, phenylacetic acid (>99%, Sigma-Aldrich, St.Louis, MO) was converted to 1-phenylpropan-2-one (P2P) by use of acetic anhydride (AR, Mallinckrodt, Paris, Kentucky) and pyridine (99+%, ACROS Organics, New Jersey, USA) via the Dakin−West reaction. 11504

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Figure 6. (A) Reaction mechanism for the production of E- and Z-enol acetates of P2P. (B) Plot of the detection of the P2P acetates.

detectability of DBK within the atmosphere hours before the simulation took place; this holds true for all masses obtained. There were no detectable atmospheric constituents that could be mistaken as a false positive for a given mass associated with a precursor or byproduct. Figure 3(C) indicates elevated levels as compared to baseline. Many portable systems have been developed utilizing membrane inlet techniques.46,47 These systems use the same principle of allowing selective permeation of an analyte through a membrane for mass analysis. Many different materials have been studied as potential materials for membrane use; polydimethylsiloxane (PDMS) is one that has shown excellent results for aromatic compounds.48 The mass spectrometer and membrane inlet in the vehicular system has been used elsewhere for analysis of benzene, toluene, ethylbenzene, and xylene (commonly known as BTEX) and polycyclic aromatic hydrocarbons (PAHs).49 Scans were repeatedly collected, and Figure 4 is a representative of those spectra. Peaks are the result of solvent or fragmentation of parent mass constituents in the manufacturing process, and those impurities have been profiled.11 The presence of alkanes is the result of fragmentation post-introduction as the choice of membrane is selective for chemistries that contain aromatics.48,49 Figure 5 illustrates

compared to baseline data obtained before the experiment began. Noticeable increases in intensity are attributed to the displacement of precursors and synthetic byproducts into the atmosphere from the experiment. Finally, the National Oceanic and Atmospheric Agency (NOAA) and Environmental Protection Agency’s (EPA) Areal Locations of Hazardous Atmospheres (ALOHA) software is used in conjunction with local weather data to provide a theoretical means of effluent plume diffusion.

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RESULTS AND DISCUSSION During the production of ATS precursors, side reactions are unavoidable and often show indications of the synthetic routes of manufacture used. Many of these reaction mechanisms are known in the literature,41,42 although the exact route may still be debated.43,44 For the Dakin−West reaction, the most commonly seen impurity, 1,3-diphenylpropan-2-one or dibenzylketone (DBK), results from a lack of excess acetic anhydride present in the reaction.45 This causes the mixed anhydride to be acylated by another mixed anhydride molecule rather than acetic anhydride and produces a dark-colored ketone impurity, as shown in Figure 3(A). The DBK impurity was tracked using the 118 m/z fragment. In Figure 3(B), baseline data shows no 11505

DOI: 10.1021/acs.analchem.5b03269 Anal. Chem. 2015, 87, 11501−11508

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Figure 7. (A) Mechanism of phenylacetylcarbinol synthesis. (B) Detection of the chemical signature.

Figure 8. Obtained data for benzyl acetate byproducts. Here, the plot indicates that wind has carried the chemical south, down the road and along the building just south of the source site.

Another common impurity results from the base-catalyzed enol tautomer of P2P being formed.45 The enol tautomer becomes more kinetically favorable with the addition of base

mass spectra of obtained P2P and unreacted excess precursor phenylacetic acid. These resultant products, in addition to other impurities elucidated below, were used in the trial. 11506

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Analytical Chemistry and condenses with acetic anhydride to form E- and Z-enol acetates of P2P, as seen in Figure 6. This plot shows more varied concentrations. The periodic high and low intensities could be accounted for due to wind. Furthermore, the operator of the vehicle periodically overlapped each area, and as chemicals were dispersed, readings of low concentrations could be attributed to an area where a once higher concentration existed and vice versa. Phenylacetylcarbinol is produced by a similar reaction proposed here, but the enol tautomer instead undergoes hydration in an anti-Markovnikov fashion across the double bond, as shown in Figure 7. This addition can be explained by the enhanced resonance available to the benzylic anion intermediate and presence of pyridine as a weak base. Incorporating the ALOHA software suite with the Google Earth plots overlays a theoretical calculation of the target chemical. Plotted in Figure 8 is 108 m/z fragment of benzyl acetate. It has been shown to be a constituent impurity of ATS synthesis.45 ALOHA uses chemical properties, such as boiling point and molecular weight of the substance, to approximate the distance of travel in weather conditions. Additional inputs account for the toxicity of the chemical, allowing for regions to be defined with exposure limits. The plume is calculated from the source location and illustrates how windage would cause drift downwind. The large structure south of the source location allowed for chemical elements to be pushed eastward along the wall of the structure. The combination of experimental data and theoretical plume predictions provide many opportunities for further trials. Given the location of an active ATS synthesis, the software can be used to predict where there are detectable constituents. ALOHA data was applied post experiment and matches well with the obtained mass data. This provides a generalized area of where to begin the search for clandestine activity.

(Syracuse, NY). All spatial images utilize Google Earth (Mountain View, CA) software.

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CONCLUSIONS The detection of chemical markers from ATS synthesis provides ample opportunities for future tests. Other illegal drugs are manufactured in the same manner. This will be further applied to detect those synthetic routes. Statistical analysis of data would provide further localization. The highly mobile platform makes rapid deployment possible. Future efforts will make the analysis more user-friendly, and real time data processing could help locate sites more rapidly. This real time processing could actively alert an operator toward a given location, zeroing in on a target manufacture. Furthermore, remaining discrete in the public domain while utilizing the system would allow for noninfringing sampling that could aid law enforcement in obtaining search warrants.

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: 940-565-4318. Author Contributions §

P.M.M. and E.M.M. contributed to this work equally.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors would like to thank Darlene Callahan and the Department of Criminal Justice for use of UNT’s Crime Scene City. This work is accomplished in conjunction with Inficon 11507

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DOI: 10.1021/acs.analchem.5b03269 Anal. Chem. 2015, 87, 11501−11508