Determination of brominated flame retardants: a proficiency test

This manuscript presents the results of a proficiency test for the determination of total bromine and several polybrominated biphenyls and diphenyl ethers (PBB and PBDE) in plastic. The test material used is a poly(ethylene terephthalate) (PET) granulate fortified with a mixture of PBB and PBDE. Up to twenty laboratories from 15 countries registered for the exercise and reported results. Homogeneity and stability were investigated to asses the adequacy of the selected test material. Laboratory results were rated with z and ζ scores according to ISO 13528. The standard deviation for proficiency assessment was set to 25 % of the assigned values. This exercise highlights the difficulties laboratories have to provide consistent values for the investigated measurands. Many participants reported underestimated measurand values; satisfactory z scores ranged from 61 to 88 %. The critical experimental parameters are identified and discussed.