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

Abstract

Abstract. Forensic evidentiary backlogs are indicative of the growing need for costeffective, 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.

A Low-Cost, Simplified Platform of Interchangeable, Ambient Ionization Sources for Rapid, Forensic Evidence Screening on Portable Mass Spectrometric Instrumentation

“…PSI has been applied broadly in the forensic community, such as quantitative determination of abused drugs in whole blood [40] and rapid detection of explosives [49] and chemical warfare agent simulants [50]. It has been shown highly proficient towards drug evidence screening on portable MS systems, as well [9,19,22,51]. Current efforts towards substrate modification are also of interest [52,53], as they offer the capability for advanced sampling strategies that should prove interesting to the forensic community.…”

“…Similar to PSI, a high voltage is then applied to perform spray-like ionization of dissolved analytes from the pyramidal egress, with no need for pneumatic assistance. PCSI is a relatively new technique, but it has already been applied to food products such as ground beef and tea leaves [31], abused pharmaceutical tablets [22], and medicinal herbs [55]. As a majority of forensic evidence encountered in the field would be in bulk phase (e.g., powders, crystals), PSCI is a promising in-situ analysis for seized drugs for its simplicity and minimalistic preparation requirements.…”

“…Direct air monitoring and headspace analysis has been demonstrated on portable MS systems by utilizing simplified atmospheric pressure chemical ionization (APCI) sources [60,61], including trace detection of toxic industrial compounds from room air [62,63] and headspace vapors of common solvents utilized in clandestine drug manufacture [19,22,64]. APCI, first reported by Horning et al, commonly employs a corona discharge to create primary reagent ions (typically a series of protonated water clusters, depending on relative humidity) via ion/molecule reactions starting with N 2 +· and O 2 +· [65].…”

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

“…All experiments were performed using a FLIR Systems AI-MS 1.2 cylindrical ion trap (CIT) mass spectrometer (FLIR Mass Spectrometry, West Lafayette, IN, USA), as previously reported when used in forensic applications [23][24][25]. The instrument possesses a factory-produced DESI source with solvent delivery provided by an on-board syringe pump.…”

Fast quantitation of pyrazole fungicides in wine by ambient ionization mass spectrometry

“…Ambient ionization techniques have been well developed in the last decade. Starting with desorption electrospray ionization (DESI) 7 and direct analysis in real time (DART) 8 , more than 40 methods have been developed, including extractive electrospray ionization (EESI) 9 , low-temperature plasma (LTP) 10 , and many others 11–21 . One of the benefits provided by these techniques is the greatly improved throughput with the sample preparation eliminated or significantly simplified.…”