Extraction-chromatographic determination of zinc dithiophosphates in engine oils

Abstract

State of the art problems of the determination of zinc dithiophosphates in engine oils are con sidered. Zinc dithiophosphates are used as multifunctional additives in engine oils and determine their anti oxidant, antiwear, and antifriction properties. The factors that prevent the determination of additives in the test samples and methods for their elimination are studied. The analytical methods used for the screening and determination of zinc dithiophosphates in engine oils are assessed. Given the complexity of the oil matrix, the procedure including the preseparation of analytes on hydroxylated silica using solid phase extraction and the separation of the base oil components and some additives by two stage extraction followed by the detec tion of analytes by high performance liquid chromatography (HPLC) should be considered the most suitable for determining zinc dithiophosphates. The proposed procedure for the determination of zinc dithiophos phates in engine oils was tested on a number of commercial samples with satisfactory results.