| 摘要 |
<p>An apparatus and method for analysing breath, in particular volatile organic compounds such as acetone in breath and for calibrating breath analysis measurements using a breath- derived background sample. Breath is sampled directly through a mouth piece where flow rate and carbon dioxide are monitored, and is in part drawn through a cold trap into a spectroscopic measurement cell, such as for carrying out cavity-enhanced absorption spectroscopy, and also in part drawn through a molecular sieve trap into a holding cell or bellows of flexible volume. Measurements are then made on the sample in this spectroscopic cell and subsequently on the background sample derived from the holding cell. The cold trap is designed to reduce the water content of the breath sample to a predetermined level by reducing the temperature of the breath to a predetermined level. Knowing the quantity of water allows the absorption cross section of water also to be known, providing a direct calibration of the response of the instrument. The molecular sieve is selected to remove water and the analyte of interest, this resulting in a breath- derived background sample which includes exhaled methane and carbon dioxide and thus provides an appropriate background level for the individual subject against which the absorption measurement on the dried breath sample can be compared to quantify the analyte of interest.</p> |
