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/PCDF in stack gas of incinerators and thermal processes had been described recently [l]. Contamination effects of PCDD/PCDF at the inner surface of the sampling device caused by the adsorption/desorption equilibrium restoration were found to be the major problem for continuous operation of the device because they lead to false emission values after very high or low emission peaks. By adding a definite amount of gaseous methanol to the stack gas in the sampling probe contaminations could be supressed and the extraction capacity of the indicator 2,3,4,7,8-pentafuran drastically increased. Furthermore, the thereby sample matrix obtained represents an optimal solvens for the subsequent continuous clean-up device because recovery rates of the indicator 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].