Preconcentration on Organic Solvent-Soluble Membrane Filter and Spectrophotometric Determination of Trace Cobalt in Biological Samples

Abstract

A sensitive and selective spectrophotometric determination of cobalt (II) using 2-(5-bromo-2-pyridylazo) -5-(N-propyl-N-sulfopropylamino)aniline (5-Br-PSAA) is described. 5-Br-PSAA reacts with cobalt to form red-violet and red colored complexes in various pH ranges and only cobalt(II) complexes, which are formed at pH 8, is concentrated on the membrane filter. After dissolving the analyte and filter in N, N-dimethylformamide(DMF), the absorbance of the DMF solution is measured at 550nm against the reagent blank as a reference. Cu(II), Fe(II) and Ni(II) give strong interference, but other metal ions do not interfere. The calibration curve shows a good proportionarity in the concentration range of 2 ppb to 50ppb cobalt(II).