Results from the second round of the international intercalibration on PCDDs, PCDFs and PCBs in a fly ash extract

The second round of an international intercalibration exercise on the determination of PCDD/DFs and planar PCBs in a fly ash extract took place in 1995/96. Thirty laboratories from around the world were participating, 25 of them were able to produce results before the expiration of the dead line. Six extracts from three batches were sent to the participants who reported the levels of all 2,3,7,8-substituted PCDD/DF congeners, PCB #77, #126 and #169 plus the total of PCDD/DFs at each chlorination level. The results showed good agreement between 21 laboratories with a RSD below 15% for the total TEQ. The results were further evaluated with multivariate statistics. Plots from principal component analyses identified analytical problems for some of the participants, but clustering of the majority of the participants.