gas-chromatographic separation of isomers shall be < 25 % peak to peak between 1,2,3,4,7,8-hxcdf and 1,2,3,6,7,8-hxcdf .
distribution of isomers by means of gas chromatography must be sufficient ( < 25 % overlap between pistes of 1,2,3,4,7,8-hxcdf and 1,2,3,6,7,8-hxcdf ) .