Determination of Titanium, Chromium, Magnesium, and Aluminum in Chromium-Based Polyethylene Catalysts by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) with Microwave Digestion

A method for the determination of titanium, chromium, magnesium, and aluminum in chromium-based polyethylene catalysts by inductively coupled plasma atomic emission spectrometry (ICP-AES) with microwave digestion was developed. Microwave digestion has become popular and attractive to users in part owing to the application of modern equipment with new technologies, such as temperature-controlled heating blocks, microwave systems, and automated digestion systems. The digestion condition was optimized concerning digestion system, proportion of acids and digestion procedure, which affords reference for the preparation of the chromium-based polyethylene catalysts samples. The reactions that can occur during the digestion process have been specified considering the fundamental thermodynamic properties of the reagents used, especially the oxidizing reagents HCl, HNO3, and H2O2. The matrix interferences of Cr on the other measured elements were investigated and eliminated by the addition of the mixed internal standard solution. According to the results, the linear correlation coefficient of the calibration curve of each element was not less than 0.9998. The detection limits of Cr, Ti, Mg, and Al were 0.00105, 0.00135, 0.00066 and 0.00234 mg L−1, respectively. With this method, the recoveries were between 97.50 and 104.0%, and the relative standard deviations (RSD, n = 6) were between 0.51 and 4.45%.