Validation of the SIFT technique for trace gas analysis of breath using the syringe injection technique

We show how our selected ion flow tube mass spectrometric technique for trace gas analysis can be used to determine the concentrations of ammonia in alveolar breath from single exhalations using both H30+ and 02+ precursor ions for chemical ionization. Thus, data are presented of the alveolar ammonia concentrations in the breath of six healthy volunteers following the ingestion of a liquid protein meal, which show that consistent values are obtained using these two precursor ions. Alveolar breath ammonia concentrations (which range from 200 to 1750 ppb in these individuals) are compared with those obtained from bag samples of breath from the same individuals.

Section: Methodsmentioning

confidence: 99%

“…This results in small fractions of NH 4 (H 2 O) 1,2 ions, and these ions have to be included into the calculation of the ammonia partial pressure. Also, hydrated hydronium ions,…”

Section: Methodsmentioning

confidence: 99%

“…are present in the carrier gas and these undergo ligand switching reactions with the breath ammonia also producing the NH 4 hydrates indicated above.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Quantification of ammonia in human breath by the selected ion flow tube analytical method using H3O+ and O2+ precursor ions

Španěl

Davies

Smith

1998

Selected ion flow tube - mass spectrometry: detection and real-time monitoring of flavours released by food products

Španěl¹,

Smith²

1999

116

This paper is concerned with the application of our selected ion flow tube mass spectrometric analytical method (SIFT-MS) to the analysis of the complex aromas of some food products. This SIFT/MS chemical ionisation technique, to date mostly applied to breath analysis in medicine and health and safety practice, involves the use of pre-selected H 3 O , NO and O 2 ions to 'soft ionise' the volatile organic compounds (VOCs) that constitute complex mixtures such as food aromas. The kinetics involved are well-defined thus allowing quantification of several trace gases simultaneously in an air sample in real time without the need for pre-calibration. In order to facilitate the interpretation of the spectra obtained for complex mixtures by SIFT/MS we have carried out detailed studies of the reactions of these three ion species with a wide variety of organic compounds including many alcohols, aldehydes, ketone, esters and organosulphur compounds. A large kinetics database has thus been created and general patterns of reactivity are seen which are shown to be invaluable for SIFT/MS analyses. Thus, the SIFT mass spectra for some specific food flavours and for the VOCs emitted by cut onion, crushed garlic and ripe banana are presented and interpreted. Finally, the temporal variations in the concentrations of some of the VOCs emitted by these food products, obtained in real time using SIFT/MS in the selected ion monitoring mode, are also presented, which demonstrate the value of this analytical technique in food research.

An investigation of the reactions of H3O+ and O2+ with NO, NO2, N2O and HNO2 in support of selected ion flow tube mass spectrometry

Španěl

Smith

2000

A selected ion flow tube (SIFT) experimental investigation has been carried out of the reactions of H3O+, NO+ and O2+ with NO, NO2, N2O and HNO2, in order to obtain the essential kinetic data for the analyses of these compounds in air using selected ion flow tube mass spectrometry (SIFT-MS). These investigations show that NO+ ions do not react at a significant rate with any of these NOx compounds and that H3O+ ions react only with HNO2 (product ions H2NO2+ (75%) and NO+ (25%)). O2+ ions react with NO (product ion NO+), NO2 (product ion NO2+) and HNO2 (product ions NO+ (75%), NO2+ (25%)), but not with N2O. We conclude that both NO and NO2 can be accurately quantified in air using only O2+ precursor ions and SIFT-MS when HNO2 is not present. However, when HNO2 is present it invariably co-exists with both NO and NO2 and then both H3O+ and O2+ precursor ions are needed to determine the partial pressures of NO, NO2 and HNO2 in the air mixture. We also conclude that currently N2O cannot be analysed in air using SIFT-MS.