On-line determination of iron(II) and iron(III) using a spectrophotometric sequential injection system Original Research Article

The application of sequential injection analysis (SIA) for metal speciation analysis is presented. The proposed method was used for the quantitative discrimination of two iron species, Fe(II) and Fe(III). Tiron was used as the chromogenic reagent for Fe(III) and total iron after Fe(II) was oxidised to Fe(III) by H2O2. The linear range is from 0.15 to 100.00 and 0.30 to 80.00 mg l−1 for Fe(III) and Fe(II), respectively, with a %R.S.D. of 1.3 and 0.8% for Fe(III) and Fe(II), respectively. The detection limit (DL) was found to be 0.10 and 0.15 mg l−1 for Fe(III) and Fe(II), respectively. The system is fully computerised and able to process 30 samples h−1.