Prior assay as an approach to flow titrations. Spectrophotometric determination of iron in alloys and ores Original Research Article

In titrimetric procedures, the number of data points can be reduced when the analyte concentration is roughly known. This aspect is emphasised in automated titrations where a foresight of the analyte concentration can be fast and easily achieved by processing known amounts of sample and titrant, and evaluating the titrant excess. This prior assay permits a previous definition of the different titrant amounts to be further added. The feasibility of this strategy is demonstrated in designing a flow-batch titrator for spectrophotometric determination of iron in steels, iron ores and similar. The method involves titration of ferrous ions by permanganate performed inside a 400 μl reaction chamber assembled in the manifold. The proposed system handles about 20 samples per hour, requires 94 μg KMnO4 per determination and yields precise results (R.S.D. ca. 1.5%, n=6) for 1.0–10×10−3 mol l−1 Fe in the injectate. Accuracy was assessed by running a standard reference material and different samples already analysed by a manual titrimetric procedure.