Abstrakt
A selected ion flow-drift tube mass spectrometric analytical technique, SIFDT-MS, extends SIFT-MS by the inclusion of a static but variable [i]E[/i]-field along the axis of the flow tube reactor in which the ion-molecule chemistry occurs. These techniques are useful for quantitative analyses of vapours present for example in environmental air, food flavour, exhaled breath, urine or cell culture headspace.
The ion axial speed is increased in proportion to the reduced field strength [i]E/N[/i] ([i]N[/i] is the carrier gas number density) and the residence/reaction time [i]t[/i], which is measured by Hadamard transform multiplexing, is correspondingly reduced as well. The essential features of SIFDT-MS and SIFT-MS are compared.
The resistive glass drift tube is demonstrated to be suitable for SIFDT experiments. The Hadamard transformation can be used to routinely determine reagent ion residence time in the flow-drift tube and also to observe differences in arrival times for different product ions.
Two-dimensional data combining arrival time and mass spectra can be obtained. The SIFDT-MS technique can be implemented in a miniature and low-cost instrument and two- or three-dimensional data can be obtained (product ion count rates as functions of [i]m/z[/i], [i]t[/i] and [i]E/N[/i]) using the Hadamard transformation.
The main features of the technique are compared and contrasted with SIFT-MS and PTR-MS and the latest results are discussed.