Improvement in breakthrough volume evaluation methods for light adsorbent traps employed for volatile organic compounds determination at atmospheric concentration levels

The use of the thermal desorption (TD) technique with light adsorbents allows for the determination of organic air pollutants at nmol/mol (ppb) level. In this work, two methods to determine the breakthrough volume (BTV) values of sampling devices are proposed as alternatives to the classic methods. The first method proposed obtains extrapolated BTV values (indirect method) and the other, obtains the direct elution profile (direct method). The main advantage of these particular methods is the possibility of working with very diluted samples which are more similar to real conditions, thus avoiding the drawbacks, due to the detection limits, usually encountered with the classic methods. Consequently, the methods proposed here exhibit better sensitivity because the organic content which remains in the device, after passing a given air volume through it, is directly analysed by TD-GC, instead of the method of detecting the organic content of the effluent from the trap. Laboratory tests show that the accuracy of the proposed methods is the same or even better than the accuracy of the classic method.