Use of an Amphiphilic Calix[4]arene with Sulfonate Functionality at the Lower Rim as a Buffer Additive in Capillary Electrophoresis

An amphiphilic calix[4]arene with sulfonate groups on the lower rim has been investigated as a buffer additive for separation of positional isomers by capillary electrophoresis. Addition of the compound to the running buffer led to successful separation of positional isomers of nitrophenols, dinitrobenzenes, and benzenediols. Association constants between the calixarene and the analytes indicated that size-selective host–guest interactions between them played a prominent role in determining the separation behavior.