Study on Thermal Desorption Method for the Analysis of BTEX in Indoor Air

One-step thermal desorption (without cryotrap, method I) and two-step thermal desorption (with two cryotraps, method II) were used for the pretreatment of BTEX (benzene, toluene, ethyl benzene, o, m, p-xylene, styrene)-containing samples. The determination coefficients (R²), precisions, detection limits and thermal desorption remaining of the two methods were compared. The results showed that determination coefficients of the standard curves were practically the same using both method I and method II ranging from 0.9924-0.9983 (except benzene in method I); Method I gave a better precision for the higher boiling-point compounds (styrene, o-xylene) while a lower precision for the lower boiling-point compounds (benzene, toluene, ethyl benzene, m, p-xylene); The detection limit and thermal desorption remaining in method II were about 50% and 12% of that in method I.