Determination of the composition of natural rosins using cyclodextrin-modified capillary electrophoresis

Abstract

Natural rosins are derived from pine tree resin. Their composition is complex and varied depending on the geographical source of the rosin and the part of the tree it is sourced from. They are used widely in industry in paints and varnishes, drug coating and as flux in soldering. Random crystallization of rosins in finished products results in problems e.g. in circuit boards, and the cause is still unclear. Rosins are composed of 90% acidic compounds and 10% neutrals. The acidic compounds are primarily abietic acid, neoabietic acid, dehydroabietic acid palustric acid and pimaric acid. The neutral compounds compose mainly of aldehydes and terpenes. The acidic composition of rosins has been reported on widely since the early 90’s through the analysis of their methyl esters by GC-MS. However, the neutral compounds of rosins have not been thoroughly investigated. In this project, rosin samples were analysed by Capillary Electrophoresis (CE) and High Performance Liquid Chromatography (HPLC). A CE method using cyclodextrin-modified buffers was developed and optimised in order to achieve the best separation of the three chemical groups of compounds present in this complex matrix. Having previously identified and quantified the acids present in the samples, this talk focuses on the identification of the neutral compounds present. Spiked samples and various simultaneous UV detection wavelengths were used to determine the identity of compound peaks. Possible links between the differences in composition of rosin samples, and their uses in industry were also addressed