Non-linearity with metal-metal ligand complex reactions in flow injection systems. Metal-thiocyanate reactions

The linearity of the standard calibration graph for the spectrophotometric flow injection determination of chloride, based on its displacement of thiocyanate from mercury(II) thiocyanate and the subsequent reaction of the thiocyanate with iron(III), was extended by the addition of nickel(II) and copper(II) to the standard reagent solution. This was done after a theoretical study of the relationship between the amount of metal ion and thiocyanate as ligand in the metal-thiocyanate complex reaction systems. The calibration graph was linear between 0 and 1200 mg l−1 for standard chloride solutions with r = 0.982 (n = 12) as opposed to 0–80 mg l−1 in the normal procedure.