Flow-injection spectrophotometric determination of copper (II) ion at low mu g L-1 levels

A highly selective, sensitive and fast determination of trace amounts of co pper (II) ion is described. The method is based on the formation of the col oured Cu(II)-N,N'-o-phenylenebis(salicylaldimine) (PBS) complex, which is t hen selectively monitored at 415 nm. To increase the interaction between co pper(II) and the colour forming reagent and preconcentrate copper(II), a mi crocolumn containing strong cation-exchange resins was placed between the i njection manifold and the spectrophotometer. The linear range of the propos ed method was 25-100 mug L-1, and the limit of detection (signal-to-noise r atio = 2) was <1 <mu>g L-1 for 20 muL injection volume of copper (II) ion s olution at a sampling rate of >50 h(-1). The relative standard deviation at the level of 25-100 mug L-1 was 0.24% for n=5. The precision and accuracy of the method was checked by analysis of a certified reference material, an d the applied to river and sea water samples.