Determination of iron(III)-iron(II) mixtures by differential-pulse polarography in solutions containing ammonium tartrate and a good buffer

ANALYSTANALYST Pub Date: DOI: 10.1039/AN9901501067

Abstract

An investigation into the determination of FeIII and FeII by differential-pulse polarography (DPP) has been carried out using supporting electrolyte solutions containing ammonium tartrate (0.10 M) and sodium chloride (0.15 M) and buffered by zwitterionic Good buffers from pH 5.4 to 8.2. At a low pH a high proportion of the analyte, FeIII, was reduced to FeII, while at a high pH, trace amounts of oxidants converted the FeII into FeIII. However, by carrying out a DPP scan in the cathodic direction in solutions buffered by 3-(N-morpholino)-1-propanesulphonic acid (MOPS)(0.10 M) or N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulphonic acid)(HEPES)(0.10 M) at pH 7.4, reasonably stable, well separated maxima corresponding to FeII oxidation and FeIII reduction were produced. These maxima were considerably more stable than those of the previously reported method using pyrophosphate as a supporting electrolyte and form the basis of a more reliable method for the determination of FeIII-FeII mixtures.

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