Determination of nine resin acids in natural gum rosins by cyclodextrin-modified capillary electrophoresis

Rosins are natural compounds derived from pine tree resin. They are used widely in industry in paints and varnishes, drug coatings and as flux in soldering. They compose of 90% acidic and 10% neutral components. Their compositions vary depending on their geographical source, and the part of the tree the rosin is sourced from. \ud Determination of resin acids using GC has been reported for the methyl esters of several resin acids including pimaric-, sandaracopimaric-, isopimaric- and abietic acid. This required derivitisation of the analytes. HPLC has also been applied, however little separation has been achieved with only dehydroabietic acid being baseline resolved\ud Therefore a more desirable approach analytically is a simple, fast and efficient separation using CE. This paper looks at the steps involved in the development of a CE method for separating and quantifying the resin acids.\ud A mixture of nine of the most common resin acids, pimaric-, sandaracopimaric-, isopimaric-, dehydroabietic-, levopimaric-, neoabietic-,7-oxodehydroabietic-, palustric- and abietic acid found in rosin was separated. Due to the structural similarities of some of the analytes it was necessary to investigate CD-modified CE to improve separation. It was found that combination of a β and a γ (see figure 1) cyclodextrin in a pH 8 tris buffer provided sufficient interaction and mobility for the acids to separate based on their hydrophobicities, which had not previously been achieved. This separation method was applied to natural rosin samples in order to identify and determine the resin acid concentration present in the samples