Development of reference procedures for the quantification of toxic metals and S in plastics

The quantitative analysis of toxic metals in plastics is very important for different sectors of industry and daily life. Many routine procedures have been established based on X-ray fluorescence or inductively coupled plasma atomic emission spectrometry. However, all of them require suitable reference materials to calibrate or validate. These reference materials ideally are being certified by reference procedures. The development of such reference procedures for sulfur and the four toxic elements cadrnium, chromium, mercury and lead in plastics is described here. The procedures are based on double isotope dilution mass spectrometry including analyte-matrix separation. The applied mass spectrometric techniques are thermal ionization mass spectrometry as well as inductively coupled plasma mass spectrometry. Memory effects of mercury and dissolution of chromium(III) oxide have been considered especially. The expanded uncertainties have been improved from the percent range down to the per mill range during the development of the procedure from the early analysis of BCR-680/681 to the recent analysis of CCQM-P106. With the fully developed procedures expanded uncertainties (k = 2) between 0.1 and 0.4% for cadmium, chromium, lead and sulfur and around 1% for mercury can be achieved. The so developed procedures have been successfully applied to the certification of reference materials as well as to intercomparisons organized by CCQM.