Microfabricated capillary electrophoresis sensor for uranium (VI)

Arsenazo III, a metallochromic ligand colorimetrically sensitive to the metal complexation of lanthanide and actinide metal ions, is applied to a capillary electrophoresis microchip for the detection of uranium (VI) and various lanthanide metal ions. The glass microchip contained 100µm deep by 200µm wide microchannels etched in a simple cross pattern with an 80mm separation channel length and an 8mm injection channel length. Detection of the Arsenazo III metal complexes is achieved using a red light emitting diode (LED) light source and a photodiode array detector. Carbowax 20M is incorporated into the background electrolyte in order to eliminate the electroosmotic flow and prevent dye adsorption on the microchannel walls. Separation of uranium from four lanthanide metal ions is demonstrated in under 2min. The addition of diethylenetriaminepentaacetic acid (DTPA) to the background electrolyte is found to be an effective means of eliminating any interference from lanthanide, transition and alkaline earth metal ions. Direct load injection of a pre-complexed metal ion mixture onto the microchannel gave a detection limit of 23ppb uranium (VI) in the presence of seven lanthanide impurities (1.5ppm each) in under 55s.