Separation of resin acids using cyclodextrin-modified capillary electrophoresis

A cyclodextrin-modified capillary electrophoretic method has been developed for the analysis of eleven common resin acids using a pH 4.5, 20 mM sodium acetate buffer containing 10% acetonitrile, 20 mM methyl-beta-cyclodextrin (MECD) and 30 mM sulfobutylether-beta-cyclodextrin (SBCD) as buffer modifi ers. At pH below their pK(a), (< 5.7-6.4) the resin acids were virtually un ionized and insoluble; however, they formed water-soluble inclusion complex es with MECD (20 mM) or SBCD (30 Mm) even at pH 4.5. The analytes were sepa rated in 25 min and, with the exception of two pairs, 12- or 14-chlorodehyd roabietic/12,14-dichlorodehydroabietic acid and dehydroabietic/palustric ac id, the remaining resin acids were baseline-separated. Analysis time was si gnificantly shortened (< 12 min) at pH 9.25 using 30 mM SBCD and 20 mM MECD in 20 Mm sodium berate. Resin acids were baseline-separated with the excep tion of two pairs, pimaric/ sandaracopimaric acid and 12- or 14-chlorodehyd roabietic/abietic acid. The addition of 7.5% methanol to the running buffer resolved the abietic acid peak. Both HPLC and micellar capillary electroki netic chromatography using 20 Mm deoxycholic acid, 10% acetonitrile in 20 M m sodium berate, pH 9.25, failed to resolve the resin acids. The simple cap illary electrophoretic method developed would be useful for the rapid separ ation and characterization of several important resin acids in pulp mill ef fluents and other contaminated samples.