[Simultaneous determination of Cd2+, Pb2+, Cu2+ and Zn2+ by reversed-phase high performance liquid chromatography]

HPLC was used in the investigation of the reaction behavior of Cd2+, Pb2+, Cu2+ and Zn2+ with mesotetrakis (4-hydroxy-phenyl)porphine (THPP) and chromatographic behavior of their complexes. The reaction and chromatographic separation parameters were optimized and a method for the simultaneous determination of Cd2+, Pb2+, Cu2+ and Zn2+ by reversed-phase high performance liquid chromatography with THPP as pre-column derivatization reagent was established. The metal-THPP complexes formed in 0.1 mol/L borate buffer (pH 10.5) by heating in 60 degrees C water bath for 20 min and were extracted into ethyl acetate-benzene mixture. The metal-THPP complexes and THPP were separated on a Prodigy ODS, 5 microns, 250 mm x 4.6 mm i.d. column with methanol-0.05 mol/L borate buffer(90:10, V/V) (pH 8.0) as eluent and detected at 437 nm (Cd2+ and Zn2+), 465 nm (Pb2+) and 416 nm (Cu2+). The detection limits of the four metal ions in 5 microL injection solution were Cd2+ 0.02 ng, Pb2+ 0.02 ng, Cu2+ 0.02 ng, and Zn2+ 0.12 ng, and the linear ranges were Cd2+ 8 ng-1.5 micrograms, Pb2+ 8 ng-3.0 micrograms, Cu2+ 8 ng-5.0 micrograms, and Zn2+ 50 ng-10 micrograms in 10 mL reaction solution. The intra-day repeatability (as RSDs) was in the range of 2.8%-4.8% and the inter-day reproducibility was in the range of 3.7%-9.7%.