Separation of niobium(V) and tantalum(V) by capillary electrophoresis with chemiluminescence detection

A new method for simultaneous determination of niobium(V) and tantalum(V) is described. Capillary electrophoresis (CE) with chemiluminescence (CL) detection was used in the separation and detection of niobium(V) and tantalum(V) which catalyze the CL reaction of luminol with hydrogen peroxide (H2O2). The mixing mode used in this work allowed the CL reagents (luminol and H2O2) and the analytes to meet simultaneously at the detection window while in conventional ion chromatography chemiluminescence (ICCL) the CL reagents are mixed in advance. Therefore, in this work the luminol as a component of the separation carrier electrolyte avoided the loss of light signal which occurs when luminol and hydrogen peroxide are mixed in advance in ICCL. Signal enhancement was achieved by sample stacking injection in the electrophoresis process. A sample volume of 20nl was injected. The metal ions were separated in less than 7min with sodium dihydrogen phosphate buffer (pH 2.5, 10mmol/l). The detection limits of this method for niobium(V) and tantalum(V) (S/N=3) are 826zmol (4.13×10-10mol/l) and 640amol (3.2×10-8 mol/l), respectively. The sensitivity of the metal ions was satisfactory.