Additive elements such as Ba, Ca, Zn, Cu, Cl, P and Mg are added to lubricating oils for improved engine performance. Although necessary, additive concentrates are very expensive and it is important that refineries blend within the required specifications using reliable and accurate analytical techniques to measure the metal concentrations.
This paper is an overview of additive element analysis in lubricating oils at the Esso Petroleum Canada Research Centre. A comparison of the two current techniques, wavelength dispersive X-ray fluorescence (WXRF) and simultaneous inductively coupled plasma emission spectroscopy (ICPES), will be described.
We will give a brief summary on the scope, theory, and methodology of each technique plus the strengths and weaknesses of each method as they relate to fresh and used oils. A comparison of the precision between WXRF and ICPES will be examined as well as the use of robotics to improve precision and turnaround time with the ICPES method.
Our hope is to give the nonexpert a better understanding of the advantages and disadvantages of WXRF versus ICPES when choosing instrumentation or methodology for analyzing additive elements in fresh and used lubricating oils.