title: Hydrogen sulphide in human nasal air quantified using thermal desorption and selected ion flow tube mass spectrometry.
abstract: The discovery that hydrogen sulphide (H2S) acts as a gasotransmitter when present at very low concentrations (sub-parts per billion (ppbv)) has resulted in the need to quickly quantify trace amounts of the gas in complex biological samples. Selected ion flow tube mass spectrometry (SIFT-MS) is capable of real-time quantification of H2S but many SIFT-MS instruments lack sufficient sensitivity for this application. In this study we investigate the utility of combining thermal desorption with SIFT-MS for quantifying H2S in the 0.1-1 ppbv concentration range. Human orally or nasally derived breath, and background ambient air, were collected in sampling bags and dried by passing through CaCl2 and H2S pre-concentrated using a sorbent trap optimised for the capture of this gas. The absorbed H2S was then thermally desorbed and quantified by SIFT-MS. H2S concentrations in ambient air, nasal breath and oral breath collected from 10 healthy volunteers were 0.12  ±  0.02 (mean ± SD), 0.40  ±  0.11 and 3.1  ±  2.5 ppbv respectively, and in the oral cavity H2S, quantified by SIFT-MS without pre-concentration, was present at 13.5  ±  8.6 ppbv. The oral cavity H2S correlates well with oral breath H2S but not with nasal breath H2S, suggesting that oral breath H2S derives mainly from the oral cavity but nasal breath is likely pulmonary in origin. The successful quantification of such low concentrations of H2S in nasal air using a rapid analytical procedure paves the way for the straightforward analysis of H2S in breath and may assist in elucidating the role that H2S plays in biological systems.
authors: Division of Medical Sciences, Northern Ontario School of Medicine, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B5E1, Canada. Department of Chemistry, Johannesburg, South Africa.
authors: Taddese
authors: T
authors: Wondimu
authors: Rui
authors: R
authors: Wang
authors: Brian
authors: B
authors: Ross
mesh_terms: D000328:Adult; D000388:Air / Q000032:analysis; D001944:Breath Tests / Q000379:methods*; D005260:Female; D006801:Humans; D006862:Hydrogen Sulfide / Q000032:analysis*; D007477:Ions; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D009055:Mouth / Q000378:metabolism*; D009297:Nasal Mucosa / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D055815:Young Adult
chemical_list: D007477:Ions; D006862:Hydrogen Sulfide