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 Mn-II 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 x 10(-6) mg l(-1) (as compared with 6 x 10(-5) mg l(-1) in solution) and expands the linear range by an order of magnitude (to 5 x 10(-6)-2.5 x 10(-3) mg l(-1)). The precision of manganese determination on the sorbent is high (the RSDs are less than or equal to 5% for greater than or equal to 6 x 10(-4) mu g Mn). Samples of tap and river water were analysed by use of the proposed sorption-catalytic technique. A rapid procedure for the determination of manganese with visual detection was also developed.