Separation and Identification of Zinc Dithiophosphates by Partition Paper Chromatography

Abstract

This paper describes the method for the separation and identification of zinc dithiophosphates having alkyl or aryl substituents by partition paper chromatography.Of a variety of solvent systems examined, the solvent system of cresyldiphenyl phosphate (stationary phase)-90/10 isooctane•n-cetane (mobile phase) was most suitable for the separation and identification of zinc dialkyldithiophosphates. Their Rf values with this solvent system increase with the number of carbon atoms in the alkyl group. Among zinc dialkyldithiophosphates having isomeric alkyl groups respectively of straight primary, branched primary and secondary, the Rf values increase in this order. The solvent system of liquid paraffin-isopropyl alcohol was found to be satisfactory for partition paper chromatography of zinc dialkyldithiophosphates having long chain alkyl groups.A large difference in the Rf values between zinc dialkyldithiophosphates having isomeric alkyl groups respectively of primary and secondary, was observed when the solvent system of polyoxyethylene octylphenylether (E. O. 10mol)-n-heptane was used and similarly, a large difference in the Rf values between zinc dialkyldithiophosphates having isomeric alkyl groups respectively of straight primary and branched primary, was observed when the solvent system of chlorinated paraffin-isopropyl alcohol was used. It is effective especially for the analysis of mixtures of zinc dialkyldithiophosphates to use these solvent systems together with the solvent system of cresyldiphenyl phosphate-90/10 isooctane•n-cetane.It was found that zinc diaryldithiophosphates can be distinguished from zinc dialkyldithiophosphates by the solvent system of chlorinated paraffin-isopropyl alcohol and identified by the solvent system of cresyldiphenyl phosphate-90/10 isooctane•n-cetane or liquid paraffin-isopropyl alcohol.Zinc dithiophosphates in commercial antioxidants and EP hydraulic oils could be identified by the above mentioned solvent systems.