The desorption purge time and thermal stability of 1,3-butadiene in a charcoal sampling tube

Abstract

Thermal desorption is a technique used in the recovery of sampled airborne organic compounds from solid adsorbent trapping media. There are several advantages of this technique over solvent desorption: 1) absence of the toxic solvent; 2) greater concentration of the sample; 3) higher detection sensitivity. Most organic compounds are known to be unstable at high temperatures. The thermal stability of the organic compounds is an important parameter that must be determined before considering a thermal desorption process. Two major variables, which affect the desorption purge time when organic compounds are desorbed from a charcoal tube by thermal means, are the temperature and carrier gas flow rate. In this study, a modified gas chromatograph apparatus was used to measure the 1,3-butadiene desorption purge time under various desorption conditions. The thermal stability of 1,3-butadiene at various temperatures was also investigated by measuring the percent recovery. The most important finding of this study is that the proportion of 1,3-butadiene recovered decreases for the desorption temperature greater than 170 OC when zero air is used as the carrier gas. The effects of temperature, carrier gas flow rate, and charcoal quantity on the desorption purge time of 1,3-butadiene are summarized in detail. From these observations, it is possible to select combinations of temperatures and carrier gas flow rates that allow quantification of 1,3-butadiene thermally desorbed from coconut charcoal packed in the glass tubes. This study suggests that at carrier gas flow rate of 23 mL/min, the desorption temperature for 1,3-butadiene on the activated charcoal is 170 OC.