Simultaneous Determination of Cu-EDTA and Its Degradation Intermediates by Capillary Electrophoresis with a Capacitively Coupled Contactless Conductivity Detector

A method of capillary electrophoresis (CE) with capacitively coupled contactless conductivity detector ((CD)-D-4) was developed to detect Cu-EDTA and its degradation intermediates simultaneously. The target compounds included oxalic acid, EDTA, Cu-EDTA, glyoxylic acid, iminodiacetic acid, formic acid and copper ion. The optimum electrophoretic conditions were determined by varying the running solution, injection voltage, injection time, and separation voltage. The anions in the reaction solution were separated and detected successfully under the conditions of 20 mmol L-1 acetate acid, electrokinetic injection of -13 kV x 10 s, and separation voltage of -15 kV. Furthermore, copper ion was detected when 20 mmol L-1 acetate acid solution, electrokinetic injection of +11 kV x 6 s and separation voltage of +13 kV were applied. The detection method was verified to track the degradation of Cu-EDTA with H2O2/UV.