INFLUENCE OF ORGANIC-SOLVENTS IN COELECTROOSMOTIC CAPILLARY ELECTROPHORESIS OF PHENOLS

The addition of organic solvents (methanol, ethanol, 1-propanol, 2-pro panol, acetonitrile) as modifiers in capillary electrophoresis (CE) si gnificantly improves peak shapes and enables the separation of positio nal isomers of substituted phenols. A reversal of the electroosmotic n ow (EOF) to reduce analysis time by migration of the anionic analytes in the same direction as the electroosmotic flow (coelectroosmotic CE) is achieved by using cetyltrimethylammonium bromide and 1,5-dimethyl- 1,5-diazaundecamethylene polymethobromide (hexadimethrine bromide, HDB , Polybrene) as EOF modifiers. The influence of various organic modifi ers on EOF, electrophoretic mobilities of the analytes, and theoretica l plate numbers is investigated. A high pH value of the buffer electro lytes above the pK(A) value of the phenols is chosen. The impact of va rious organic modifiers and the influence of the chain length of the a lcohols on the separation behavior of alkyl phenols is investigated.