A shoebox-sized, 10-kg, handheld mass spectrometer, Mini 10, based on a rectilinear ion trap mass analyzer has been designed, built, and characterized. This instrument has evolved from a decade-long experimental and simulation program in mass spectrometer miniaturization. The rectilinear ion trap has a simplified geometry and high trapping capacity, and when used with a miniature and ruggedized pumping system, it allows chemical analysis while the instrument is being carried. Compact electronics, including an air core RF drive coil, were developed to control the instrument and to record mass spectra. The instrument runs on battery power, consuming less than 70 W, similar to a laptop computer. Wired and wireless networking capabilities are implemented. The instrument gives unit resolution and a mass range of over m/z 500. Tandem mass spectrometry capabilities are implemented using collision-induced dissociation, and they are used to provide confirmation of chemical structure during in situ analysis. Continuous monitoring of air and solution samples is demonstrated, and a limit of detection of 50 ppb was obtained for toluene vapor in air and for an aqueous naphthalene solution using membrane sample introduction.

Experimental data and simulations of trapped-ion motion are used to characterize the phenomenon of compound-dependent mass shifts in a quadrupole ion trap mass spectrometer. The ratio of axial to radial dimensions of the ion trap and the nature and pressure of the bath gas are identified as experimental variables which influence the chemical mass shift. Systematic changes in chemical shifts occur with changes in the chemical structure of the ion, for example between members of a homologous series of alkylbenzene molecular ions. Simulations, performed using a new version of the program ITSIM, indicate that the mass shift is the result of two interacting factors:  (i) delayed ion ejection from the trap during the mass analysis scan due to field imperfections associated with the end-cap electrode apertures and (ii) the compound-dependent modification of this delay by collisions with the bath gas. Both elastic collisions and inelastic collisions, including those which lead to dissociation, appear to contribute to the shortening of the delay and hence to affect the magnitude of the chemical mass shifts.

The analytical performance of a fieldable cylindrical ion trap (CIT)-based miniature mass spectrometer is described. A detailed description of the instrument itself is to be found in the immediately preceding paper (Patterson, G. E.; Guymon, A. J.; Riter, L S.; Everly, M.; Griep-Raming, J.; Laughlin, B. C.; Ouyang, Z.; Cooks, R. G., Miniature Cylindrical Ion Trap Mass Spectrometer, Anal. Chem. 2002, 24, 6145-6153). Applications employing the MS/MS and MSn capabilities of the miniature instrument and analytical performance criteria are given here. The limit of detection for methyl salicylate, introduced as the pure vapor, is estimated as 1 pg. The resolution, R = m/delta m, where delta m, measured as full width at half-maximum, is estimated as 100. Monitoring of organic compounds in air is performed using a permeation membrane introduction device coupled to the mass spectrometer. Water monitoring is performed using an external membrane introduction mass spectrometry (MIMS) system, with acetophenone and toluene serving as model compounds. Data are given for chemical warfare agent simulants, methyl salicylate, and dimethyl methyl phosphonate (DMMP) in air. On-line detection of menthol vapor emitted from a cough drop is reported. Methyl salicylate in air gives a recognizable mass spectrum at 400 ppb in the ambient system, while use of a heated membrane brings the detection limit down to 10 ppb.

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...

A recently constructed miniature mass spectrometer, based on a cylindrical ion trap (CIT) mass analyzer, is used to perform ion/molecule reactions in order to improve selectivity for in situ analysis of explosives and chemical warfare agent simulants. Six different reactions are explored, including several of the Eberlin reaction type (M. N. Eberlin and R. G. Cooks, Org. Mass Spectrom., 1993, 28, 679-687) as well as novel gas-phase Meerwein reactions. The reactions include (1) Eberlin transacetalization of the benzoyl, 2,2-dimethyloximinium, and 2,2-dimethylthiooximinium cations with 2,2-dimethyl-1,3-dioxolane to form 2-phenyl-1,3-dioxolanylium cations, 2,2-dimethylamine-1,3-dioxolanylium cations and the 2,2-dimethylamin-1,3-oxathiolanylium cations, respectively; (2) Eberlin reaction of the phosphonium ion CH3P(O)OCH3+, formed from the chemical warfare agent simulant dimethyl methylphosphonate (DMMP), with 1,4-dioxane to yield the 1,3,2-dioxaphospholanium ion, a new characteristic reaction for phosphate ester detection; (3) the novel Meerwein reaction of the ion CH3P(O)OCH3+ with propylene sulfide forming 1,3,2-oxathionylphospholanium ion; (4) the Meerwein reaction of the benzoyl cation with propylene oxide and propylene sulfide to form 4-methyl-2-phenyl-1,3-dioxolane and its thio analog, respectively; (5) ketalization of the benzoyl cation with ethylene glycol to form the 2-phenyl-1,3-dioxolanylium cation; (6) addition/NO2 elimination involving benzonitrile radical cation in reaction with nitrobenzene to form an arylated nitrile, a diagnostic reaction for explosives detection and (7) simple methanol addition to the C7H7+ ion, formed by NO2 loss from the molecular ion of p-nitrotoluene to form an intact adduct. Evidence is provided that these reactions occur to give the products described and their potential analytical utility is discussed.