Determination of catalyst metal residues in polymers by X-ray fluorescence

Commercial polyethylenes produced by Ziegler-Natta, Philips and metallocene technology were analyzed by X-ray fluorescence spectroscopy. Synthetic standards using wax matrix was shown to be suitable for the calibration curve in comparison to those prepared by milling and grinding virgin polymer mixed with standard metal oxide as matrix. The detection limits obtained for the studied metal in the different polymers were: 12 mg kg−1 for Mg, 0.8 mg kg−1 for Ti, 1.6 mg kg−1 for Cr, 1.2 mg kg−1 for Zr and 1.9 mg kg−1 for V. For comparative reasons, the determination of residual metal content by Rutherford backscattering spectrometry (RBS) and total-reflection X-ray fluorescence spectrometry (TXRF) is also discussed.