A Water-Soluble Tetraethylsulfonate Derivative of 2-Methylresorcinarene as an Additive for Capillary Electrophoresis

A water-soluble tetraethylsulfonate derivative of 2-methylresorcinarene (TESMR), an aromatic-based, bowl-shaped macrocycle, was used as an additive in capillary electrophoresis. Several phenol derivatives are used as analytes to demonstrate the effect of this highly charged additive. TESMR is observed to interact differently with a mixture of positional isomers and other types of phenol derivatives. A comparative study of separations with two charged additives, TESMR and sulfobutyl ether-β-cyclodextrin (SBE-β-CD), provided insight into the selectivity exhibited by these additives. The influence of buffer pH, ionic strength, and organic modifier content on separation and peak shape is investigated. Peak asymmetry caused by the use of highly charged additives at lower pH is minimized by the addition of small amounts of a polar aprotic organic solvent to the run buffer. The effects of mixing a charged additive with a neutral additive are also discussed.