Separation of phenylureas by capillary electrochromatography on porous graphitic carbon

Summary In this work the potential of porous graphitic carbon (PGC) as a new stationary phase in, capillary electrochromatography has been explored. Its behavior under the action of an applied potential is described for the separation of phenylureas. First, it was shown that porous graphitic carbon enables high efficiency in capillary electrochromatography over a wide range of mobile phase velocities. It was then demonstrated that this material might be responsible for degradation of the solutes at frit-PGC interfaces. Although electrolytic degradation reactions are suspected to occur on this type of conductive material, voltamperometric measurements furnished no clear evidence. A specific injection procedure is proposed for avoiding degradation of the solutes at the inlet interface before their chromatographic separation. Comparison of the retention behavior of phenylureas on PGC in liquid chromatography and in capillary electrochromatography show that the retention propertiets of PGC are altered by application of an electrical field, because this modifies the donor-acceptor interactions between the solutes and the stationary phase.