MSACL 2019 EU Abstract

The Effect of Concentrations of Major Metabolites on Quantification of Minor Volatile Compounds in Breath by SESI-MS

Kseniya Dryahina, Suman Som, Patrik Spanel
J. Heyrovský Institute of Physical Chemistry AV ČR, v. v. i., Dolejškova 3, Prague, Czechia

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Kseniya Dryahina (Presenter) J. Heyrovsky Institute of Physical Chemistry

Presenter Bio: Kseniya Dryahina is a researcher at the Department of Chemistry of Ions in Gaseous Phase at the J. Heyrovsky Institute of Physical Chemistry, Czech Academy of Sciences, Prague. She graduated in physics at Sumy State University, Ukraine and in 2008 received PhD from Charles University, Prague (Czech Republic). Her research focusses on ion chemistry involved in quantification of volatile trace compounds in air, exhaled breath and in the headspace of biological samples. Over the past 10 years collaborating with clinicians in interdisciplinary studies, she has been involved and led several clinical studies of exhaled human breath including diagnosis of bacterial infections.

Relevant Financial Disclosures (within past 24 months) Salary J. Heyrovsky Institute of Physical Chemistry of the CAS, v. v. i. Conflict mitigation NOT REQUIRED.

INTRODUCTION: Secondary electrospray ionization-mass spectrometry (SESI-MS) is a highly sensitive innovative real time technique for analyses of complex gaseous mixtures such as human breath. Accurate quantification of gaseous analytes cannot be currently done without internal standards. Breath is a complex mixture containing several hundreds volatile organic compounds (VOCs) present at concentrations from pptv to ppmv. When compounds are present at elevated concentrations that can significantly decrease the reagent ion signal in SESI, the secondary and ternary reactions take place, additional products are observed and quantification based on calibration is compromised. However, accurate quantification of trace gases in air based on chemical ionisation by reagent ions and ion-molecule reaction kinetics can be achieved by selected ion flow tube mass spectrometry (SIFT-MS) that is less sensitive than SESI-MS.

OBJECTIVES: The primary objective of this study is describe the effect of elevated concentrations of acetone, ammonia and ethanol (as measured by SIFT-MS) on quantification of minor volatile analytes by SESI-MS. The specific objective is to understand the general principles of gas phase ion chemistry at atmospheric pressure that underlies SESI quantification.

METHODS: Gaseous mixtures simulating breath, natural and spiked breath samples were analysed using SESI-MS and in parallel by real-time quantitative SIFT-MS method. The peak heights in SESI-MS spectra were related to SIFT-MS measured concentrations and changes in SESI sensitivity of analyses of minor volatile metabolites thus were calculated.

RESULTS: Sensitivities for SESI-MS quantifications were obtained for a range of compounds including acetic acid, sulphur compounds, alcohols and ketones as a function of concentration of ammonia, acetone and ethanol spiked to the breath sample in range up to 3000 ppb (10x physiological baseline, for acetone corresponding to ketogenic state). The data show that sensitivity for acetic acid is reduced by a factor of 1.2. For methanethiol the effect is similar at a factor of 1.3.

CONCLUSION: Presence of acetone, ammonia and ethanol in breath affects SESI-MS quantification by up to a factor of 1.3 due to complex ion chemistry taking place in humid atmospheric pressure air. This effect can be explained by kinetics of gas phase ion-molecule reaction sequences involving hydrated protonated molecules.
ACKNOWLEDGEMENT: Funded by GACR project 18-12902S.