Modified continuous sampling and clean-up device for the determination of PCDD/PCDF in waste gases of incinerators and thermal processes

A continuous sampling and clean-up device for the determination of PCDD/PCD F in stack gas of incinerators and thermal processes had been described rec ently [1]. Contamination effects of PCDD/PCDF at the inner surface of the s ampling device caused by the adsorption/desorption equilibrium restoration were found to be the major problem for continuous operation of the device b ecause they lead to false emission values after very high or low emission p eaks. By adding a definite amount of gaseous methanol to the stack gas in t he sampling probe contaminations could be supressed and the extraction capa city of the indicator 2,3,4,7,8-pentafuran drastically increased. Furthermo re, the thereby sample matrix obtained represents an optimal solvens for th e subsequent continuous clean-up device because recovery rates of the indic ator isomer also increased due to prevented adsorption effects. Altogether, the I-TEQ values calculated from the indicator isomer concentration of the modified sampling device are in excellent agreement with those measured by the EN-guideline CEN/TC 264/WG1 (a) [2]. (C) 1999 Elsevier Science Ltd. Al l rights reserved.