Chapter 4 - Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) and Flowing Afterglow Mass Spectrometry (FA-MS) for the Determination of the Deuterium Abundance in Water Vapour

Abstract

This chapter discusses the novel methods needed for the determination of trace gas metabolites in breath for clinical diagnosis and therapeutic monitoring. The novel selected ion flow tube mass spectrometric method (SIFT-MS) and flowing afterglow mass spectrometric method (FA-MS) can be used for the on-line, real time analysis of the deuterium abundance in breath water vapor and in the headspace of aqueous liquids, including blood, urine and dialysate fluid. The FA-MS results are in greater precision because of the larger ion count rates involved. The microwave discharge that is exploited may introduce small fractions of impurity ions. A rapid, non-invasive method to determine total body water in patients suffering from end-stage renal failure would have great value if it could be used directly in the clinical environment. Deuterium isotope dilution within the body coupled with a new analytical approach offers a route to it. The SIFT-MS can provide cleaner analyses, as the H30 + precursor ions are selectively introduced into the helium carrier gas. However, longer ion counting integration times need to be used to obtain an acceptable precision for the D/H analyses in SIFT-MS.