Gas Concentrator with an Activated Carbon Adsorbent for Breath Analysis

The detection of volatile organic compounds (VOCs) in respired breath is important because it can serve as a noninvasive means for obtaining information regarding an individual's health status and for diagnosing diseases. However, it is difficult to detect respired VOCs because the concentration is very low, i.e., on the order of ppt to sub-ppm. Current commercially available small-sized VOC detectors are unable to detect sub-ppm-level VOCs; thus, large-scale analytical equipment, such as gas chromatography systems and mass spectrometers, are required for breath analysis research. To realize practical application of the breath analysis method, performance measures, such as the selectivity and sensitivity of a small-sized VOC detector, must be improved. Here, we propose a gas concentrator for breath analysis and evaluate its adsorption and desorption performance. The gas concentrator concentrates the low level of VOCs in exhaled breath to a level that is detectable by commercial VOC detectors. In this study, we also considered the practicability of our proposed device in terms of collection convenience, storability, and transportability of the exhaled sample. We experimentally demonstrated that the gas concentrator could capture gas molecules without reducing the pressure of the gas. Furthermore, we demonstrated that the process of collecting the target gas molecules from a large amount of initially injected gas and subsequently transferring it to a small volume of carrier gas increased the gas concentration by at least 25 times. Consequently, the adsorption and desorption rates of the gas concentrator were found to reach approximately 90% and 70%, respectively. It is expected that the proposed gas concentrator can be combined with a gas analyzer or detector for breath analysis-based disease diagnosis.