Flow-injection simultaneous determination of iodate and periodate by spectrophotometric and spectrofluorometric detection

A simple and accurate procedure for simultaneous spectrophotometric and spectrofluorometric determinations of iodate and periodate in aqueous media has been developed. The determination of periodate is based on the selective oxidation of Alizanin Navy Blue to produce a fluorescent compound, that can be found by flow-through spectrofluorometric detection (lambda(ex)=370 nm, lambda(em)=516 nm). On the other hand, periodate and iodate react with iodide to produce iodine, which is determined by spectrophotometric detection at 349 nm. The injected sample was split into two streams, one of which was directly treated with Alizarin Navy Blue and passed to the flow cell of the spectrofluorometer. A fluorescence signal at 516 nm was due to periodate. The other stream was treated with iodide and sulfuric acid and then passed through the flow cell of the spectrophotometer. The increase in absorbance at 349 nm was due to periodate and iodate. The influences of the acid concentration, reagent concentration and manifold variables were studied. The effect of diverse ions on the determination of periodate and iodate by the proposed method was also investigated. Periodate and iodate can be determined in the range of 1.0x10(-5) - 2.2x10(-4) M and 1.0x10(-5) - 2.0x10(-4) M, respectively. Within the 3 sigma detection limit was 3.5x10(-6) M for periodate and 1.0x10(-6) M for iodate, respectively. Applying this method to the analysis of iodate and periodate in artificial fresh-water samples was successfully carried out.