A miniature cylindrical ion trap mass spectrometer is described, and preliminary data are presented. Functionality and performance of laboratory-scale instruments have been maintained to the extent possible in this battery-operated mass spectrometer. Capabilities include tandem mass spectrometry experiments. Custom-designed electronic components include the RF scanning and amplification system, data acquisition components, and lens power supplies, as well as a custom-software application. Direct leak and membrane introduction inlet systems are used for sample introduction. A mass/charge range of approximately 250 Th with unit mass resolution has been demonstrated.

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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.

This Tutorial is an introduction to statistical design of experiments (DOE) with focus on demonstration of how DOE can be useful to the mass spectrometrist. In contrast with the commonly used one factor at a time approach, DOE methods address the issue of interaction of variables and are generally more efficient. The complex problem of optimizing data-dependent acquisition parameters in a bottom-up proteomics LC-MS/MS analysis is used as an example of the power of the technique. Using DOE, a new data-dependent method was developed that improved the quantity of confidently identified peptides from rat serum.

Construction, optimization, and testing of a novel single-sided configuration for a semi-permeable [poly(dimethylsiloxane); PDMS] membrane introduction system for mass spectrometry is described. On-line detection of semi-volatile organic compounds of environmental interest is shown, including lindane (a pesticide), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) (an explosive), butylated hydroxytoluene (BHT) (an antioxidant), 1,2-dichlorobenzene, dimethylmethyl phosphonate (DMMP) (a chemical warfare agent simulant) and naphthalene. The technique has limits of detection in the sub-ppb range. with rise times of 4 to 7 s and fall times of 12 to 36 s and a response that is linear over 4 orders of magnitude (from 0.1 ppb to 1000 ppb for DMMP). The cycle time, from crude air sampling to acquisition of results, is approximately 1 min. No sample preparation is necessary.