Measurement of short-chain fatty acids in low concentration using detector tube

Abstract

Short-chain fatty acids (especially C4 and C5) are involved in the critical components of the odor from the livestock excretion. However, the concentrations of the short-chain fatty acids are often too low to analyze even when it strongly smells. In this work, a measurement method of short-chain fatty acids in low concentration was developed using detector tube. In this method the short-chain fatty acids were concentrated in the adsorbent prior to the detector tube measurement. It was verified that quarts powder was the most suitable adsorbent for this method, which also made it possible to use the circumambient air for the carrier gas of the thermal desorption from the adsorbent. The temperature fluctuation and the condensation of the water vapor were compensated by installing the U-tube between adsorbent and a detector tube. The influence of the interferential species was negligible in this method mainly because of their irreversible adsorption on the quartz adsorbent. Finally it was demonstrated that the concentration of short-chain fatty acids were able to be determined in the headspace gas from composting pig dung.