Automatic flow analysis method to determine traces of Mn2+ in sea and drinking waters by a kinetic catalytic process using LWCC-spectrophotometric detection

• A rapid and simple analyzer for Mn2+ determination is presented.
• The liquid wave-guide capillary cell improves method sensitivity.
• Automation exploiting MSFIA and LOV enhances method's efficiency and precision.
• Potential interferences were eliminated by using Dowex resin for sample clean-up.
• This analyzer can be portable allowing in-situ and field measurement.

A new automatic kinetic catalytic method has been developed for the measurement of Mn2+ in drinking and seawater samples. The method is based on the catalytic effect of Mn2+ on the oxidation of tiron by hydrogen peroxide in presence of Pb2+ as an activator. The optimum conditions were obtained at pH 10 with 0.019 mol L−1 2'2 bipyridyl, 0.005 mol L−1 tiron and 0.38 mol L−1 hydrogen peroxide. Flow system is based on multisyringe flow injection analysis (MSFIA) coupled with a lab-on-valve (LOV) device exploiting on line spectrophotometric detection by a Liquid Waveguide Capillary Cell (LWCC), 1 m optical length and performed at 445 nm. Under the optimized conditions by a multivariate approach, the method allowed the measurement of Mn2+ in a range of 0.03–35 µg L−1 with a detection limit of 0.010 µg L−1, attaining a repeatability of 1.4% RSD. The method was satisfactorily applied to the determination of Mn2+ in environmental water samples. The reliability of method was also verified by determining the manganese content of the certified standard reference seawater sample, CASS-4.

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