Gas chromatography double focusing sector-field ICP-MS as an innovative tool for bad breath research

Abstract

The development of a new methodology for the determination of volatile sulfur compounds (VSCs) in human breath by gas chromatography (GC) coupled to ICP-double focusing (DF)-MS is described. The coupling between GC and ICP-DF-MS was achieved by means of an interface built in our laboratory. The different parameters affecting the chromatographic separation and the sulfur-specific detection by ICP-DF-MS were optimised in order to achieve best response for the isotope 32S. Selected chromatographic conditions are given using a capillary column for sulfur compounds (SPB-1 Sulfur). The effect of using cold plasma conditions and a shielded torch, available in the double focusing instrument, were also evaluated to obtain the best analytical performance characteristics for 32S monitoring. Using the selected instrumental conditions for this GC-ICP-DF-MS system, it was possible to obtain detection limits between 8 and 33 ppb (v/v), depending upon the sulfur chemical species, and precisions of around ±7.5% at 800 ppb (v/v) levels. The developed hybrid method was successfully applied to the determination of volatile sulfur compounds in the head-space of vials containing human saliva. The saliva is incubated in anaerobic conditions at 37 °C in order to reproduce the rotting processes, that are caused in the mouth by anaerobic microbiota, and which are responsible for more than 80% of bad breath cases described in the literature.