Implementation of DART and DESI ionization on a fieldable mass spectrometer

Abstract

A recently developed prototype mobile laboratory mass spectrometer, incorporating an atmospheric pressure ionization (API) interface, is described. This system takes advantage of the small size, lower voltage requirements, and tandem MS abilities of the cylindrical ion trap mass analyzer. The prototype API MS uses small, low-power pumps to fit into a 0.1-m 3 self-contained package weighing <45 kg. This instrument has been adapted to allow rapid interfacing to electrospray ionization, desorption electrospray ionization, and direct analysis in real-time sources. Initial data indicate that these techniques provide rapid detection and identification of compounds for quality control, homeland security, and forensic applications. In addition, this instrument is self-contained and compact, making it ideally extensible to mobile laboratory and field analyses. Initial MS and MS/MS data for analyses of drugs, food, and explosives are presented herein. O ver the past 15 years, efforts toward implementing mass spectrometry (MS) in the field have steadily grown with particular focus on environmental, forensic, defense, and security applications [I, 2]. Many of the previously developed fieldable MS instruments use gas chromatography (GC-MS) because of the high degree of confidence obtained using GC retention times and electron ionization (EI) mass spectral matching [3][4][5][6]. The specificity of GC-MS comes at the expense of time, with individual analyses often taking in excess of 10 min (not including sample preparation). Reducing the amount of time required for chemical identification requires separation-free MS. In the absence of chromatography, tandem MS (MS/MS) improves confidence for the identification of individual components in mixtures [7]. With spectral acquisition rates > 1 Hz, atmospheric pressure ionization (API) techniques such as electrospray ionization (ESI), desorption electro spray (DESI), and direct analysis in real time (DART), a fieldable API MS system capable of MS/MS is of high value to environmental, forensic, defense, and force protection agencies. There have been few attempts to construct fieldable MS instruments with an API interface to date [8][9][10][11] because of the difficulty of displacing the gas load of the atmospheric inlet.The cylindrical ion trap (CIT)-a simplified geometry of the hyperbolic quadrupole ion trap capable of Address reprint requests to Dr. Mitch Wells, Griffin Analytical Technologies, LLC, R&D, 3000 Kent Avenue, West Lafayette, IN 47906, USA. E-mail: mitch.wells@icxt.com performing MS n analyses-has been shown to be amenable to miniaturization [12][13][14] while maintaining benchtop-quality performance characteristics. The miniaturized CIT enables a smaller vacuum system with smaller pumps that consume less power, providing a fieldable instrument. Although GC-MS instruments currently dominate the portable mass spectrometry industry, estimates indicate that the confidence for molecule identification by MS/MS is about that provided with GC-MS (when combining MS information w...

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

“…To this end, validation studies that follow standard practices [45] and recommendations from gatekeepers like the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) [46] are required to ensure subsequent court admissibility. While broad validation efforts have been undertaken for ambient ionization methods conducted on lab-scale MS instrumentation, such as the work of Gurdak and coworkers at National Physical Laboratory (NPL) in assessing inter-laboratory repeatability and constancy of DESI-MS [47], similar efforts utilizing portable MS systems for forensic applications have been limited to categorical assessments like limits of detection (LOD) and linearity [48,49]. Cooks and co-workers have assessed LODs for explosives residues [50,51] and drugs of abuse [52] using their lineage of miniaturized MS systems, as well as demonstrated quantitative toxicological analysis of biofluids [53,54].…”

What can we learn from ambient ionization techniques?

“…Another fascinating development that took place in parallel was the development of portable or miniaturized mass spectrometers [9 -14]. An entire issue of this journal [JASMS 2008, 19(10)] has been devoted to this topic under the heading "Harsh Environment Mass Spectrometry" [12,13,[15][16][17][18][19][20][21][22]. Although all of the field-portable mass spectrometers available nowadays are less powerful in terms of sensitivity, mass range, and mass resolving power than their laboratory-based counterparts, the vision is clearly to combine suitable atmospheric pressure sources with portable mass spectrometers to run analyses in subway systems, airports, at sports events, in restaurants, supermarkets, wholesale markets, and perhaps in the future even in the average home.…”

Direct Detection of Pharmaceuticals and Personal Care Products from Aqueous Samples with Thermally-Assisted Desorption Electrospray Ionization Mass Spectrometry

“…As with any analysis involving heating of analyte, thermally-labile compounds could exhibit fragmentation in precursor MS scans, increasing spectral complexity. Coupled with field-portable mass spectrometric instrumentation [43][44][45], this methodology could be used as a stand-alone sensor in long-term monitoring programs and remediation efforts, allowing the determination of new contaminants and detection of degradation and metabolic products of those already established.…”