scope:

1) EN 1948-4 was elaborated with special carefulness and was validated by extensive validation measurements covering a wide concentration range. Nevertheless the described selection of the sampling standards (see EN 1948-4, Table 1) causes co-elution problems of PCB 127 and PCB 105 on the most common columns. The use of the columns HT-8 or Agilent XLB can avoid these co-elution problems, but they are not so common for routine analyses. The sampling standard PCB 127 was chosen in order to monitor the similar and most toxic congener PCB 126 and is of special importance for plants which mainly emit PCBs. In order to avoid the co-elution problems during routine analyses a more flexible specification is given and the following footnote to EN 1948-4, Table 1, is added: Footnote b) Sampling standards: Attention should be paid to possible co-elution problems of PCB 127 and PCB 105 on certain commercially available columns. If the co-elution problems cannot be avoided, it is allowed to omit the sampling standard PCB 127. 2) In order to avoid any misunderstanding with regard to the sampling compartments to be spiked with labelled standards a reference to EN 1948-1 should be added to the first sentence of EN 1948-4, Clause 6.2: ""The sampling standards (see Table 1) shall be added to the different sampling media before sampling and the extraction standards shall be added to the samples before extraction according to EN 1948 Part 1.