Chiral Separation of α-hydroxy Acids by Capillary Electrochromatography Using the Cathodic Detergent CTAB as Mobile Phase Additive to Speed up Analysis Time

摘要

In order to speed up the analysis time, working with negatively charged compounds in capillary electromigration techniques often requires to change direction of the EOF. Negatively charged compounds intend to migrate towards the anode and are normally retained by the counter migrating EOF. Therefore the positively charged detergent cetyltrimethylammoniumbromide (CTAB) was used as mobile phase additive for the chiral separation of α-hydroxy acids in capillary electrochromatography (CEC). A 25 % particle loaded Ristocetin A continuous bed (CB) was used as stationary phase to separate a set of mandelic acid derivatives. Using mandelic acid and 4-bromo-mandelic acid as model substances the effect of different CTAB concentrations in the mobile phase on the migration time and the resolution was tested. It could be shown that with an increasing concentration of the CTAB the migration time decreased. The addition of CTAB to the mobile phase is a serious alternative to copolymerizing an anionic charge providing substances such as diallyl dimethylammonium chloride (DADMAC) in CB technology. (doi: 10.5562/cca1902)