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

• Published in: Analytica chimica acta Vol. 416; no. 2; pp. 231 - 237
• Main Authors: Honorato, Ricardo Saldanha, Zagatto, Elias Ayres G, Lima, Ricardo Alexandre C, Araújo, Mário César U
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 10.07.2000; Elsevier
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; Flow-batch system; Iron alloys; Iron determination; Iron ores; Prior assay; Spectrometric and optical methods; Spectrophotometric titration; Iron ores; Flow-batch system; Iron alloys; Spectrophotometric titration; Iron determination; Prior assay; Performance evaluation; Photometric titration; Transition metal Ions; Chemical analysis; Iron ion; Iron ore; Optimization; Iron base alloys; Quantitative analysis; Operating conditions; Ultraviolet visible spectrometry
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/S0003-2670(00)00899-0

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 KMnO 4 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.