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Towards standardization in the analysis of breath gas volatiles

Despite growing interest and considerable progress in breath research over the last decade, standardized practices for the sampling and analysis of breath gas volatiles remain elusive. The primary reasons for this are (a) the rich chemical diversity of exhaled breath that covers an extensive range of volatile organic compounds at highly varied concentrations, (b) the vast disparity in the analytical tools employed, (c) diverse study goals and (d) the presence of (unidentified) confounders. These aspects place stringent but divergent demands on sampling and analysis: each analytical tool, target compound and concentration range requires its own specific protocol and in many cases the latter two are not even known a priori. The ongoing rapid developments and constant discoveries in the field of breath research and the lack of established best practices in breath gas sampling and analysis currently preclude an acceptable overall standardization of these methods. This paper addresses these manifold issues and suggests a framework that separately considers individual stages of sampling and analysis with a view to establishing standardization in the analysis of breath gas volatiles to suit different target compounds and analytical technologies.