Abstract: Two methods, namely monochromatic wavelenth dispersive X-ray fluorescence spectrometry(MWDXRF) and microcoulometry, were used to measure the chlorine content in pyrolysis oil from waste plastics. The effects of sample homogeneity, matrix influence, and coexistence of multiple elements on the measurement results were investigated. The application effects of the two methods in different laboratories were also verified. The results show that when using the MWDXRF method, the influence on the test results of the chlorine element is relatively small when the sulfur mass fraction in the sample is less than 0.5% and the oxygen mass fraction is less than 5%. When using the microcoulometry method, the influence of sulfur element on the chlorine element can be ignored when the sulfur mass fraction is less than 2%. The detection limits of the two methods are 3 μg/g and 0.3 mg/L ,respectively, and the spiked recovery rates are between 92% and 106%. During the actual measurement process, the microcoulometry method is subject to interference from brominated flame retardants present in the waste plastic pyrolysis oil. The test result actually represents the total halogen content in the waste plastic pyrolysis oil, so the measured value is higher than that obtained using the MWDXRF method.The two methods provides reliable data support for the development of low-impurity oil production technology from waste plastics.

Key words: pyrolysis oil from waste plastics, chlorine content, MWDXRF, microcoulometry, homogenization, detection limit, spiked recovery rate