Automated simultaneous determination of metal ions by use of variable flow rates in unsegmented systems

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Abstract
Two methods for the simultaneous determination of zinc and copper and of calcium and magnesium, based on the use of flow-rate gradients and spectrophotometric detection in unsegmented systems, are reported. The underlying chemistries of the determinations are a ligand-exchange reaction and a pH change, respectively, in completely continuous and flow-injection manifolds. By automatically changing the ligand concentration or pH, one can ascertain the contribution of each ion to the recorded signal. The performance of the two proposed methods was tested on both synthetic and real samples, involving the simultaneous determination of zinc and copper and of calcium and magnesium. Relative standard deviations between 1.5 and 5%, were found for the precision of the proposed methods.