Selected ion flow tube mass spectrometry (SIFT‐MS) for on‐line trace gas analysis

Abstract

Selected ion flow tube mass spectrometry (SIFT-MS) is a new analytical technique for the real-time quantification of several trace gases simultaneously in air and breath. It relies on chemical ionization of the trace gas molecules in air/breath samples introduced into helium carrier gas using H(3)O(+), NO(+), and O(2) (+.) precursor ions. Reactions between the precursor ions and trace gas molecules proceed for an accurately defined time, the precursor and product ions being detected and counted by a downstream mass spectrometer, thus effecting quantification. Absolute concentrations of trace gases in single breath exhalation can be determined by SIFT-MS down to ppb levels, obviating sample collection and calibration. Illustrative examples of SIFT-MS studies include (i) analysis of gases from combustion engines, animals and their waste, and food; (ii) breath and urinary headspace studies of metabolites, ethanol metabolism, elevated acetone during ovulation, and exogenous compounds; and (iii) urinary infection and the presence of tumors, the influence of dialysis on breath ammonia, acetone, and isoprene, and acetaldehyde released by cancer cells in vitro. Flowing afterglow mass spectrometry (FA-MS) is briefly described, which allows on-line quantification of deuterium in breath water vapor.

The Use of SIFT-MS in Profiling the Faecal Volatile Metabolome in Horses with Colic: A Pilot Study

“…SIFT-MS has been described in detail previously [3] so details are not given here. Data were collected using the Mk2 instrument with a flow rate corresponding to a pressure of 0.008 Torr.…”

“…The identities and concentrations of various components were determined using the on-line database containing reaction rate coefficients, developed from numerous detailed selected ion flow tube (SIFT) studies of various classes of compounds (alcohols, aldehydes, ketones, hydrocarbons, etc.) with the three precursor ions [3,42]. In addition, data containing count values at each m/z value were collated and analysed (see below).…”

“…For this reason, other techniques have been developed, and one such technique is selected ion tube mass spectrometry, SIFT-MS. The details of this technique have been extensively covered elsewhere [3,4] so are not included here. The advantages of SIFT-MS are that it is rapid, quantitative and relatively sensitive and the data are readily converted for multivariate analysis of spectral profiles if required.…”

Development of a device for sampling cattle breath

“…Details of how it works are described in detail elsewhere (Smith and Spanel, 2005) so will not be given here. Analysis of cattle breath samples was carried out by attaching the Nalophan bag containing the breath sample to the capillary inlet of the SIFT-MS. After a few seconds, the absolute, on-line real-time analyses of selected components of breath were obtained down to the parts-per-billion by volume (ppbv) level (ppbv describes gas concentration on a volume-per-volume ratio) and the concentrations of volatile compounds calculated using the kinetics database in the SIFT-MS on-board computer.…”

On-line detection of human skin vapors

“…Until the recent development of desorption electrospray ionization (DESI) [6] and its variant extractive electrospray ionization (EESI) [7], such studies were dominated by gas chromatography-mass spectrometry (GC-MS) [3, 4, 8 -10], which requires sample collection and preconcentration, and is time consuming. Selected ion flow tubemass spectrometry (SIFT-MS) [11] has provided realtime information on skin emanations for relatively volatile species such as acetone [12]. Proton transfer reaction-mass spectrometry (PTR-MS) claims parts-pertrillion (ppt) sensitivities [13] and has permitted on-line monitoring of UV-induced lipid peroxidation products from human skin and its dependence on the fatty acid composition of the skin [14].…”