Speciation of Mn(II) and Mn(VII) by on-line spectrophotometric sequential injection analysis Original Research Article

An on-line sequential injection analysis system with spectrophotometric detection using 4-(2-pyridylazo) resorcinol as reagent is proposed for the speciation of Mn(II) and Mn(VII). The sampling frequency is 30 determinations per hour. The linear range for Mn(II) is 0.020–0.500 mg/l with a detection limit of 0.005 mg/l and for total Mn 0.025–0.550 mg/l with a detection limit of 0.008 mg/l. The % RSD is 0.27 and 0.34 for Mn(II) and Mn(VII), respectively (n=10). Chemical masking of Fe and Al was achieved by on-line addition of a 0.1 mol/l NaF solution. The proposed system yielded results that compare very well with standard methods.