Petroleum products and lubricants are routinely analyzed for their elemental content for various reasons. Conventional methods for the sample preparation of petroleum products and lubricants like dilution or ashing suffer from severe drawbacks. Microwave-assisted acid digestion according to ASTM D7876 is a beneficial approach to achieve reliable results in a short time frame.
The concentrations of silicon, aluminum, vanadium, nickel, iron and sodium in crude and residual oils are used to define their quality and value. High amounts of nickel and vanadium in crude oil can deactivate catalysts during processing, but also initiate corrosion in motors and boilers during combustion when present in fuels. Silicon and aluminum present in residual fuel oils cause abrasion within the combustion engine. Products like lubricating oils are tested before use to determine the concentration of additives (which contain metals such as calcium, copper, magnesium, phosphor, sulfur and zinc), which is an important quality control parameter. Prior to measurement utilizing modern measuring techniques such as ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry) samples have to be transferred into a measurable (liquid, removed matrix) form.