Results of the 1st to the 4th Proficiency Testing on Determination of Hazardous Elements in Plastics

The Japan Society for Analytical Chemistry carried out proficiency testing on the determination of hazardous elements (lead, cadmium, chromium, mercury and bromine) in polyester disks or chips four times from 2003 to 2007. The number of laboratories that participated was 140 at the most (2nd) and 104 at the least (4th). The analytical methods applied in the testing were chemical analysis and X-ray fluorescence analysis. The concentration levels of the analytes were both low and high ; at low concentration, it was about 1 μg g−1 for Hg and 5∼10 μg g−1 for other elements, and about 10-times at a high concentration in 1st PT. In 2nd∼4th PT, it was 20∼30 μg/g−1 level for each element at low concentration, and 2∼3 times at high concentration. More than 80% of the laboratories obtained z score of less than 2 in absolute value, which represents "satisfactory". The uncertainties were generally larger in X-ray fluorescence analyses than in chemical analyses. However, it was reverse in the case of Br. This would have been caused by incomplete chemical decomposition of the samples. From an estimation of the correlation of the analytical results between two analytical methods using the En number, some points were shown to be improved in the practice of X-ray fluorescence analysis, such as in selecting kinds of reference materials, or in a matrices correction of the sample.