Optimization of the Conditions of Analysis of Exhaled Air by Gas Chromatography–Mass Spectrometry for the Noninvasive Diagnostics of Lung Cancer

Abstract

We optimized procedures for the collection, preparation, and storage of samples of exhaled air and the conditions for determining volatile organic compounds in exhaled air by gas chromatography–mass spectrometry (GC–MS), the presence or change in the concentration of which can be caused by lung cancer. The analysis circuit includes group adsorption preconcentration followed by the thermal desorption and determination of analytes by GC–MS. Polymer bags of a Tedlar^® film were used for sample collection. The conditions and periods of the storage of samples in bags and adsorption tubes are determined. A method for cleaning and conditioning bags is proposed. For preconcentrating exhaled air components, we used hydrophobic adsorbents (Porapak™ P, Porapak™ Q, and Tenax^® TA) and three-section tubes containing Tenax^® GR, Carbopack™ B, and Carbosieve^® S-III. Their relative efficiency was evaluated by assessing the residual background of gas emission from the adsorbent, the magnitude of the analytical signal, the efficiency of adsorption/desorption, and the efficiency of storage. The conditions for the preconcentration of volatile organic compounds (volume and rate of aspiration, time, and temperature of thermal desorption) are optimized. The main volatile organic compounds in the exhaled air of conditionally healthy volunteers were identified, and their concentrations are evaluated.