The zone electrophoresis of lubricating oil additives

Abstract

Electrophoresis can provide useful separations of lubricating oil additives. The feasibility studies were based on thin-layer electrophoresis with silica gel G plates in non-aqueous (mainly pyridine-acetic acid) and mixed aqueous solvent (ethanol-water) buffer media as well as with agarose and polyacrylamide gel support systems.

The migration behaviour of various polymer, sulphonate, salicylate, phenate and dialkyldithiophosphate types of additives is discussed. Generally, the dialkyldithiophosphate additive anions showed the greatest mobilities, followed by the sulphonates, salicylates and phenates, while the polymer-type reaction products of polyisobutenylacrylic acid or polyisobutenylsuccinic anhydride with tetraethylenepentamine were immobile.

Thin-layer electrophoresis based on ethanol-water-boric acid-sodium acetate buffer systems, coupled with a chromatographic stage in the second dimension, merits further attention. Gel electrophoresis is also promising and the disc techniques might be developed as a finger-printing method for the characterisation of additives.