SEPARATION AND SENSITIVE DETERMINATION OF METAL-IONS BY CAPILLARY ZONE ELECTROPHORESIS WITH -PYRIDYLAZO)-5-(N-PROPYL-N-SULFOPROPYLAMINO)PHENOL

Capillary electrophoresis of 22 metal ions was examined with a visible light-absorbing chelating agent, -pyridylazo)-5-(N-propyl-N-sulfoprop ylamino)phenol (5-Br-PAPS). The metal chelates separated in a capillar y were measured at 550 nm by on-column visible absorption detection. I n a standard procedure, carriers (electrophoretic buffers) containing the chelating agent and pH buffer components were used, and sample sol utions containing excess amounts of the chelating agent were injected using a vacuum injection method (about 1 x 10(-8) dm(3)). Fourteen met al ions were detected at pH 8.7, and the apparent electrophoretic mobi lities (-mu(ep), 10(-4) cm V-1 s(-1)) were as follows: Ag+, -4.21; Co2 + (Co3+), 1.37; V-IV, 1.74; Pd2+, 2.36; Mn2+ and Hg2+, 2.43; Ni2+, 2.4 8; Fe2+, Fe3+ and Cu2+, 2.50; Cd2+, 2.55; Zn2+, 2.58; Pb2+, 2.62; and Ti-IV, 3.27. By lowering the pH of the carrier, the separation of meta l ions was improved, and the apparent electrophoretic mobilities at pH 4.9 were as follows: Ag+, -6.50; Cd2+, -3.78; Zn2+, -2.78; Pb2+, -2.2 1; V-IV, 0.17; Mn2+, 0.48; Hg2+, 0.57; Cu2+, 0.60; Co2+ (Co3+), 1.37; V-V, 2.01; Ni2+,12.34; Fe2+, 2.47; and Pd2+, 2.55. At pH 4.9; these me tal ions were separated within 7 min by using a fused-silica capillary (50 mu m i.d.) of a 50 cm effective length at an applied voltage of 3 0 kV. The detection limits obtained by the standard procedure at pH 4. 9 were as follows (mol dm(-3)): Fe2+ and Co2+ (CO3+), 5 X 10(-8); CU2, 3 X 10(-7); Zn2+, pb(2+) and V-IV, 5 X 10(-7); and Cd2+, 1 X 10(-6). The method was applied to the determination of trace amounts of cobal t contained as impurities in nickel salts.