Determination of iron species in wine by ion-exchange chromatography--flame atomic absorption spectrometry

The direct coupling of ion-exchange chromatography to flame atomic absorption spectrometry (AAS) has been achieved by employing a Babington type nebuliser. The system enables all the processes on the column to be followed directly at flow-rates of between 1 and 5 ml min-1. The potential of the system was investigated for the determination of various iron species in synthetic samples containing iron(II) and iron(III) in ionic or chelated form by employing various ion-exchange (Dowex 50-X8, Dowex 1-X8) and sorptive (Amberlite XAD-2) resins, respectively. In some instances where direct coupling was impossible, owing to the physical properties of the effluent or eluent, conventional analyses of chromatographically separated iron species were performed by flame AAS. The optimum concentration range, limit of detection and reproducibility of measurement were also determined for a particular column capacity. When direct coupling was employed, the detection limit for the separated iron species was 15 micrograms with a relative standard deviation (RSD) of +/- 3% and, using the conventional method of analysis, 2-5 micrograms with an RSD of +/- 1%. On the basis of these results the system was applied to the determination of the ratio of iron(II) to iron(III) in wines.