Simultaneous determination of iron and copper by third-derivative solid-phase spectrophotometry

A simultaneous microdetermination of iron and copper at sub-mug/L level by solid phase derivative spectrophotometry has been developed. The compounds TPTZ (2,4,6-tripyridyl-,3,5-triazine) and Neocuproine (2,9-dimethyl-1,10-phenanthroline hydrochloride), were used as chromogenic reagents to form a blue iron complex and an orange copper complex, respectively (pH = 5.0), which are fixed and concentrated on a cation-exchange resin sephadex sp C-25. The influence of experimental variables on the retention of the complexes on the resin are discussed. The signals in derivative units were measured directly on the solid, packed in a I mm spectrophotometric cell. The characteristic amplitude of the signals at 622.0 and 477.0 nm in third-derivative spectra are useful for quantitative determination of iron (0.195-120 ng mL(-1): RSD=1.8%) and copper (0.451-300 ng mL(-1). RSD 1.3%). The method was applied to the iron and copper determination in different types of water, respectively