The determination of antioxidants is divided into three methods. Methods A and B now describe the determination of amines and phenols separately. Both use LSV (Linear Sweep Voltammetry) for the determination process, as before. Finally, Method C introduces a new technique, DPV (Differential Pulse Voltammetry).
In this case, amines and phenols are determined sequentially, but a second solvent component is added between the two steps. With the introduction of Method C, additional apparatus for the determination of antioxidants can also be used.
Before publication, the suitability of the revised standard must be verified by means of a successfully completed ring trial. For this purpose, 18 laboratories examined 34 sample pairs of fresh and used oils in accordance with the draft of the new standard. OELCHECK handled the sample logistics and homogenised a total of 1,224 samples, filled them and sent them to laboratories all over the world.
A huge effort for OELCHECK, but a win for lubricant analysis
The ageing process to which all lubricants are subjected during their use is essentially dominated by the oxidation of the base oil. Antioxidants are added to the oils to effectively slow down this ageing process. These are mainly additives based on amines and phenols. Yet over time, these additives break down. This increases the risk of oxidation products forming, which in turn can lead to the formation of paint-like deposits in the lubricated system.
This is why antioxidant content is determined
In particular, the content of amines and phenols as well as their changes over the service life are used as an early warning system for hazards to the lubricated system due to deposit formation. The analysis procedure is carried out in accordance with the specifications of standard D9671 of the ASTM (American Society for Testing and Materials).