Sorption–Catalytic Determination of Manganese Directly on a Paper-based Chelating Sorbent
A hybrid technique based on a catalytic reaction carried out on the surface of a paper-based sorbent is proposed. It is shown that MnII exhibits its catalytic action in the oxidation of 3,3′,5,5′-tetramethylbenzidine with periodate in aqueous solution as well as on filter-paper with or without attached diethylenetriaminetetraacetate (DETATA) groups. Optimum conditions differ for the reaction in solution and on filter-paper. For equal catalyst concentrations, higher initial reaction rates are attainable on the filter-papers. Preconcentration of manganese on the DETATA sorbent combined with the subsequent catalytic reaction improves the selectivity, reduces the limit of determination down to 5 × 10–6 mg l–1 (as compared with 6 × 10–5 mg l–1 in solution) and expands the linear range by an order of magnitude (to 5 × 10–6–2.5 × 10–3 mg l–1). The precision of manganese determination on the sorbent is high (the RSDs are ≤5% for ≥6 × 10–4 µg Mn). Samples of tap and river water were analyzed by use of the proposed sorption–catalytic technique. A rapid procedure for the determination of manganese with visual detection was also developed.