Speciation of metals in solution by flow injection analysis. Part 2. Determination of iron(III) and iron(II) in mineral process liquors by simultaneous injection into parallel streams

Abstract

An alternative approach to that described in Part 1 for the speciation of mixed oxidation state metals is described. It employs parallel colorimetric flow injection manifolds with simultaneous sample introduction by coupled injection valves. An application of the approach is reported for the determination of iron(II) and iron(III) with particular reference to mineral process liquors.

The system can operate at up to 120 injections per hour using injected sample volumes of 20 µl for each manifold. The working ranges are 0.5–180 p.p.m. of iron(III) and 0.5–120 p.p.m. of iron(II). Acid stability and interference studies in relation to mineral samples are reported, and also a novel use of the simplex optimisation procedure to minimise interference from copper(II) ions.