Electrochemically modulated chromatography-separation of catechol-containing compounds

A novel liquid chromatographic system that incorporates electrochemical control of stationary phase composition as an additional variable for optimizing and fine tuning separations has been developed. The electrochemically-modulated liquid chromatographic (EMLC) system consists of 4 gm spherical glassy carbon (GC) particles connected as the working electrode in a three-electrode cell arrangement. Electrochemically-induced changes in the excess charge at the GC surface prior to elution are used to alter the capacity factors of analytes over a wide range. This ability also provides a variable pathway for performing a gradient type elution through modification of the excess charge at the GC surface during analyte elution. This has led to the development of novel separation approaches that are analogous to gradient elution liquid chromatography, but are accomplished without changes in mobile phase composition. Results using this system for the manipulation of the elution of a variety of aromatic analytes, pharmaceutical compounds, and amino acids will be presented. In addition, studies which examined the coating of the GC spheres with electroactive species to enhance the control over stationary phase composition will be discussed.