Christopher C. Mulligan

Low-temperature plasma probe for ambient desorption ionization.

A low-temperature plasma (LTP) probe has been developed for ambient desorption ionization. An ac electric field is used to induce a dielectric barrier discharge through use of a specially designed electrode configuration. The low-temperature plasma is extracted from the probe where it interacts directly with the sample being analyzed, desorbing and ionizing surface molecules in the ambient environment. This allows experiments to be performed without damage to the sample or underlying substrate and, in the case of biological analysis on skin surfaces, without electrical shock or perceptible heating. Positive or negative ions are produced from a wide range of chemical compounds in the pure stateand as mixtures in the gaseous, solution, or condensed phases, using He, Ar, N2, or ambient air as the discharge gas. Limited fragmentation occurs, although it is greater in the cases of the molecular than the atomic discharge gases. The effectiveness of the LTP probe has been demonstrated by recording characteristic mass spectra and tandem mass spectra of samples containing hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT) from poly(tetrafluoroethylene) (PTFE) surfaces where limits of detection are as low as 5 pg. Other performance characteristics, when using a commercial ion trap mass spectrometer, include 3-4 orders of magnitude linear dynamic range in favorable cases. Demonstration applications include direct analysis of cocaine from human skin, determination of active ingredients directly in drug tablets, and analysis of toxic and therapeutic compounds in complex biological samples. Ionization of chemicals directly from bulk aqueous solution has been demonstrated, where limits of detection are as low as 1 ppb. Large surface area sampling and control of fragmentation by a simple adjustment of the electrode configuration during operation are other demonstrated characteristics of the method.

Rapid screening of synthetic cathinones as trace residues and in authentic seizures using a portable mass spectrometer equipped with desorption electrospray ionization

RATIONALE Recently, the surge in synthetic cathinone abuse has become a matter of public concern. With the influx of confiscated synthetic cathinones dramatically on the rise, laboratory workloads are expected to increase at a similar rate. This prompts the need for rapid analytical methods capable of detecting and identifying such compounds. METHODS A ruggedized, portable ion trap mass spectrometer capable of desorption electrospray ionization mass spectrometry (DESI-MS) was used to rapidly characterize various synthetic cathinones. Target analytes were directly analyzed as trace residues on various substrates and as major components in authentic, powder-based forensic evidence. Physical transfer swabs can also be examined with this method, allowing efficient screening of large areas and geometrically complex samples. RESULTS Method validity was tested on trace residues, mock forensic samples, and authentic evidentiary seizures, yielding low- to sub-ng detection limits from several substrates of interest to crime scene investigation. Analyte confirmation was accomplished through MS(2) analysis, providing characteristic fragmentation similar to that reported in literature. High-throughput analysis was demonstrated with no significant instrumental carryover, even for powdered samples. The robustness of this DESI-MS method to multi-component samples was examined, marked by high chemical specificity. CONCLUSIONS Coupling DESI-MS with portable instrumentation allowed sensitive and selective examination of synthetic cathinones from various substrates, in complex mixtures, and directly from mock and authentic forensic evidence. This instrumental method has the potential to assess the evidentiary value of forensic samples at crime scenes, reducing backlogs and expediting criminal investigations.

QuEChERS multiresidue method validation and mass spectrometric assessment for the novel anthranilic diamide insecticides chlorantraniliprole and cyantraniliprole.

The gas-phase dissociation reactions of chlorantraniliprole (Rynaxypyr) and cyantraniliprole (Cyazypyr) have been studied in triple-quadrupole, ion trap, and orbitrap mass spectrometers equipped with electrospray and desorption electrospray ion sources, revealing the formation of odd-electron fragment ions, the structures of which were elucidated. The odd-electron fragments were unusually abundant, and their formation is proposed to occur via a tricyclic intermediate. The applicability of the QuEChERS multiresidue method for the quantitation of chlorantraniliprole and cyantraniliprole was also assessed in this study. Four matrices representative of oily, watery, acidic, and dry crop groups were tested, with a targeted limit of quantitation (LOQ) of 0.01 mg/kg. Average recoveries ranged between 87 and 107%, with relative standard deviations (RSD) of ≤ 8%. Linear calibration functions with correlation coefficients r > 0.99 were obtained. The study provides an expansion of the QuEChERS method to include anthranilic diamides and a mass spectrometric assessment for these two novel agrochemical active ingredients.

Analytical Validation of a Portable Mass Spectrometer Featuring Interchangeable, Ambient Ionization Sources for High Throughput Forensic Evidence Screening

AbstractForensic evidentiary backlogs are indicative of the growing need for cost-effective, high-throughput instrumental methods. One such emerging technology that shows high promise in meeting this demand while also allowing on-site forensic investigation is portable mass spectrometric (MS) instrumentation, particularly that which enables the coupling to ambient ionization techniques. While the benefits of rapid, on-site screening of contraband can be anticipated, the inherent legal implications of field-collected data necessitates that the analytical performance of technology employed be commensurate with accepted techniques. To this end, comprehensive analytical validation studies are required before broad incorporation by forensic practitioners can be considered, and are the focus of this work. Pertinent performance characteristics such as throughput, selectivity, accuracy/precision, method robustness, and ruggedness have been investigated. Reliability in the form of false positive/negative response rates is also assessed, examining the effect of variables such as user training and experience level. To provide flexibility toward broad chemical evidence analysis, a suite of rapidly-interchangeable ion sources has been developed and characterized through the analysis of common illicit chemicals and emerging threats like substituted phenethylamines. Graphical Abstractᅟ

Monitoring the clandestine synthesis of methamphetamine in real-time with ambient sampling, portable mass spectrometry

The collection, transport and processing of evidence found at clandestine laboratory installations is a challenging task for forensic practitioners, as samples are often of high magnitude and complexity, as well as located in exceedingly unsafe conditions. Direct sampling, portable mass spectrometers coupled with ambient ionization methods have been reported for forensic applications and have the potential to fulfill the requirements of clandestine laboratory evidence processing, allowing on-site identification of chemical evidence in its native state and expediting criminal investigations. To demonstrate this potential, a portable MS system coupled with simplified DESI, PSI, and APCI ionization sources, was utilized to monitor two common synthetic routes for clandestine methamphetamine production and screen representative evidence types resulting from these installations. Specific evidence examined in these studies included bulk powdered precursor and product, reaction intermediate slurries, and gaseous headspace of utilized solvents emanating from storage media and reaction vessels. Of note, the harsh, complicated nature of the collected samples did not affect molecular identification. Comparison studies between the employed ionization methods showed that the analysis of evidence via PSI was marked by enhanced spectral intensity in comparison to DESI. Results obtained during this study demonstrate the ability of ambient sampling, portable MS instrumentation to conclusively identify a clandestine methamphetamine operation regardless of the synthesis stage.

Combining a portable, tandem mass spectrometer with automated library searching – an important step towards streamlined, on-site identification of forensic evidence

Ambient sampling, portable mass spectrometers have the potential to revolutionize forensic chemical analysis by allowing evidence screening to take place at the native locale, expediting criminal investigations and easing the burden on backlogged forensic laboratories. To evaluate the usability of such a system coupled with ambient ionization techniques, tandem MS spectra were obtained for a variety of forensically-relevant analytes and compared to an established reference library, the “Wiley Registry of Tandem Mass Spectral Data, MSforID” (Wiley Registry MS/MS), with an end goal of allowing automated chemical identification for non-technical user operation. Samples of interest included 25 positive controls, 4 negative controls, and 3 samples of authentic powder-based drug evidence. Of the 69 MS/MS spectra collected at varying collision-induced dissociation (CID) energies for the positive control samples, 68 of the spectra produced relative average match probabilities (ramp) values high enough to result in “true positive” identifications for all 25 samples tested. None of the negative control samples resulted in false-positive identifications when both obtained ramp values and visual comparison of spectra were considered. Of note, all powdered drug evidence samples examined were correctly identified by the commercial library, showing high promise for use in routine drug evidence screening. The ability for in-source fragmentation and structural isomers to produce false positive/negative responses was also investigated.

Screening of cosmetic ingredients from authentic formulations and environmental samples with desorption electrospray ionization mass spectrometry

A rapid and sensitive method based on desorption electrospray ionization mass spectrometry (DESI-MS) has been utilized for the detection of chemicals related to cosmetic products without prior preparation. DESI-MS was used to rapidly screen target compounds at ambient conditions, allowing the investigation of surface-bound residues, complex chemical matrices, and components of authentic cosmetic formulations. This high-throughput method routinely achieved low nanogram detection limits, and quantitative ability was demonstrated with decent linearity and precision. Continuous, direct analysis of cosmetic impurities in drinking water matrices was also validated, implementing thermal assistance into the ionization source design to increase overall sensitivity.

The development and assessment of high-throughput mass spectrometry-based methods for the quantification of a nanoparticle drug delivery agent in cellular lysate

The safe use of lipid-based drug delivery agents requires fast and sensitive qualitative and quantitative assessment of their cellular interactions. Many mass spectrometry (MS) based analytical platforms can achieve such task with varying capabilities. Therefore, four novel high-throughput MS-based quantitative methods were evaluated for the analysis of a small organic gene delivery agent: N,N-bis(dimethylhexadecyl)-1,3-propane-diammonium dibromide (G16-3). Analysis utilized MS instruments that detect analytes using low-resolution tandem MS (MS/MS) analysis (i.e. QTRAP or linear ion trap in this work) or high-resolution MS analysis (i.e. time of flight (ToF) or Orbitrap). Our results indicate that the validated fast chromatography (FC)-QTRAP-MS/MS, FC- LTQ-Orbitrap-MS, desorption electrospray ionization-collision-induced dissociation (CID)-MS/MS and matrix assisted laser desorption ionization-ToF/ToF-MS MS methods were superior in the area of method development and sample analysis time to a previously developed liquid chromatography (LC)-CID-MS/MS. To our knowledge, this is the first evaluation of the abilities of five MS-based quantitative methods that target a single pharmaceutical analyte. Our findings indicate that, in comparison to conventional LC-CID-MS/MS, the new MS-based methods resulted in a (1) substantial reduction in the analysis time, (2) reduction in the time required for method development and (3) production of either superior or comparable quantitative data. The four new high-throughput MS methods, therefore, were faster, more efficient and less expensive than a conventional LC-CID-MS/MS for the quantification of the G16-3 analyte within tissue culture. When applied to cellular lysate, no significant change in the concentration of G16-3 gemini surfactant within PAM212 cells was observed between 5 and 53 h, suggesting the absence of any metabolism/excretion from PAM212 cells.

Balancing the utility and legality of implementing portable mass spectrometers coupled with ambient ionization in routine law enforcement activities

Ambient sampling, portable MS systems have the potential to allow field processing of forensic evidence, as well as serve as a flexible investigative tool during routine law enforcement activities. However, the underlying legal implications of evidentiary data require the discretion of practitioners to ensure both lawful and ethical usage. Herein, practical and theoretical usage scenarios in traffic control stops are investigated using paper spray ionization-mass spectrometry (PSI-MS) on a portable, ruggedized instrument to demonstrate the field utility for law enforcement personnel, particularly in prompting “probable cause” searching of vehicles. Specific applications include the detection and identification of trace level contraband found as surface residues on automotive surfaces, in the presence of latent fingerprints, and in conjunction with emerging evidence types like adulterated beverages and electronic cigarette liquids. In addition, the current state of U.S. search and seizure law is examined in an effort to discern the presumed legal usage modes from the full analytical potential of the technique. These studies, in turn, can assist in predetermining the investigatory and legal impacts of field deployment of similar instrumentation in policing activities.

Trace-Level Screening of Chemicals Related to Clandestine Desomorphine Production with Ambient Sampling, Portable Mass Spectrometry

Desomorphine is a semisynthetic opioid that is responsible for the psychoactive effects of a dangerous homemade injectable mixture that goes by street name “Krokodil.” Desorption electrospray ionization (DESI) and paper spray ionization (PSI) are implemented on a portable mass spectrometer for the direct analysis of desomorphine and precursor reagent codeine from multiple substrates of potential relevance to clandestine drug laboratory synthesis and paraphernalia seizure. Minimal sample preparation required for analysis and portability of the instrument suggest the potential for rapid, on-site analysis of evidence, a highly desired benefit for forensic science and law enforcement practitioners. Both DESI-MS and PSI-MS can generate spectra consistent with preceding data obtained using traditional ionization methods, while demonstrating detection limits in the low- to sub-ng levels.