Self-Classified Topic Area(s): Breath and VOC Analysis
Analyses of Volatile Organic Acids in Exhaled Breath Using Secondary Electrospray Ionization Mass Spectrometry (SESI-MS)
Suman Som, Frantisek Pehal, Patrik Spanel and Kseniya Dryahina J. Heyrovsky Institute of Physical Chemistry, Academy of Science of the Czech Republic, Prague, Czech Republic
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Suman Som (Presenter) J. Heyrovsky Institute of Physical Chemistry
Presenter Bio: I am a postdoctoral research fellow in J. Heyrovsky Institute of Physical Chemistry in the department of Chemistry of Ions in Gaseous Phase with Dr. Kseniya Dryahina.
Relevant Financial Disclosures
(within past 24 months)
No relevant financial relationship(s) to disclose.
Abstract
Introduction: Human breath is a complex mixture containing endogenous metabolites and exogenous compounds. Carboxylic acids represents an interesting class of metabolites. There are several reports about volatile organic acids related to various diseases; such as hexanoic acid in gastro-esophageal cancer, propanoic acid in lung cancer [1], unsaturated fatty acids in irritable bowel disease and acetic acid in cystic fibrosis [2] with concentration ranging from pptv to ppbv. Secondary electrospray ionization mass spectrometry (SESI-MS) is a highly sensitive real time technique for online analyses of trace amounts of VOCs in exhaled breath.
Objectives: Primary objective of the study is to quantify volatile carboxylic acids concentrations by SESI-MS in exhaled breath and headspace of biological samples.
Methods: To develop SESI-MS quantification, the breath and headspace samples were analysed using SESI-MS and in parallel by real-time quantitative selected ion flow tube mass spectrometry (SIFT-MS) method.
Results: The bespoke SESI ion source was optimized for trace volatile acid analyses. Carboxylic acid were analysed in exhaled breath samples and headspace of biological samples using both SESI-MS and SIFT-MS. The relative ionization sensitivities were thus obtained for a series of volatile carboxylic acids. It was found that for acetic acid the sensitivity was 73000 per ppbv (in the units as given by Excalibur software) in dry air. The range of linearity was up to 200 ppbv. In humid sample corresponding to breath sensitivity decreased to 9800 per ppbv. Similar changes were observed for propionic (dry 706000, humid 4700) and butyric acids (dry 3x10^6, humid 2900) noting that the linearity improved in accord with decreased sensitivity. The trends in variability of sensitivities can be explained by ion-chemistry reactivity schemes.
Conclusion: SESI-MS can be used for quantification of volatile carboxylic acids present amongst metabolites in exhaled breath, serum and other biological samples. The variation in ionization efficiencies is related to proton affinities, dipole moments and gas phase acidities. Humidity plays a major role in actual analytical sensitivity and calibration must consider this.
Acknowledgement: The study was funded from Czech Science Foundation by GACR project 18-12902S “Secondary electrospray ionization mass spectrometry (SESI-MS) for quantification of gaseous analytes in air, headspace and breath”.
References:
1. Queralto N et al 2014 J. Breath Res. 8 027112.
2. Dryahina K et al 2018 J. Breath Res. 12 016002.
= Discovery stage.
= Translation stage.
= Clinically available.
