Determination of Fe(III) and total Fe in wines by sequential injection analysis and flame atomic absorption spectrometry Original Research Article

The sequential determination of Fe(III) and total Fe in Portuguese table wines by sequential injection analysis (SIA) with flame atomic absorption spectrometry (FAAS) at a sampling rate of 18 samples h−1 is described. The determination of Fe(III) is based on the extraction with MIBK of the complex formed between Fe(III) and thiocyanate by using an on-line device for gravimetric analysis previously described for FIA systems, as liquid–liquid extraction module for organic phases less dense than water. Afterwards, the determination of total iron is accomplished by sending a small sample aliquot directly to the FAAS nebulizer. The injection of about 1.8 ml of sample enabled the determination of Fe(III) ranging between 0.10–6.00 mg l−1. The injection of sample volumes of 83, 125, or 333 μl enabled the determination of total iron contents ranging between 1.50–15.00, 0.50–10.00, or 0.25–5.00 mg l−1, respectively. The linear regression analysis of the results obtained for the two parameters with the proposed procedure and those provided by the reference methods (colorimetry for Fe(III) and FAAS for total Fe) led to the following relationships: [SIA]=0.05(±0.31)+0.98(±0.10)×[colorim.] for Fe(III) and [SIA]=−0.14(±0.29)+1.03(±0.04)×[FAAS] for total Fe.