Estudo da determinação espectrofotometrica de zinco e cobre em sistemas de analise por injeção em fluxo

AUTOR(ES)
DATA DE PUBLICAÇÃO

1986

RESUMO

The importance of zinc and determinations in different materials has led to the development of several analysis, many of these have become inadequated and the development of faster methods with low reagent consumption has become desirable. Flow Injection Analysis (FIA) is a method in whinch a large number of samples can processed in a short time with low reagent consumption and acceptable precision and accuracy. May different configurations can be used, determined by the type of sample, the available quantities of analyte and reagent, the reaction involved, etc.Thus, the best experimental conditions fo the determination of zinc and copper with the organic complexing agent zincon were studied using diferent FIA systems. Reversed FIA, wich consists of injecting small volumes of reagents (40 ml)into the flowing sample stream, was used for the sequential determination of both metals. This was possible because of the isntability of the zinc-zincon complex in presence of an EDTA solution. The solution containing both the zinc-zincon and copper zincon complexex passed through the flow cell and total absorbance was measured. The zinc-zincon complex was destroyed by addition of a dilute EDTA solution. Another passage through the cell provided the copper absorbance. The zinc concentration was obtained by difference. Under optimized conditions the calibrations are linear over the range 0-1.5 mg.ml for both elements. The calculated detection limit is 11 ng.ml for zinc and 8 ng.ml for copper. Using the reversed system with the individual ions, the calculated detection limits are 6 ng.ml for zinc and 4 ng.ml for copper. In the merging-zones configuration, which reduces the reagent consumption and permits its recovery, Beer s law is obeyed up to 8 mg.ml for both zinc and copper with a detection limit of 12 and 11 ng.ml, respectively. The confluence configuration permits an infinite volume introduction into the carrier stream and is linear up to 10 mg.ml for zinc and 8 mg.ml for copper under the optimized conditions. The calculated detection limits are 9 ng.ml, respectively. The reversed confluence system is linear up to 2 mg.ml for zinc and 1,5 mg.ml for copper with detection limits of 3 ng.ml and 3 ng.ml, respectively. The flow rate varied from 2,3 to 2,6 ml.min, depending on the system studied. Thus, analaysis up to 100 samples/hour were possible. The dispersion phenomenon, as well as the effect of various ion on teh determination of zinc and copper, was studies for all investigated systems.

ASSUNTO(S)

espectrofotometria quimica analitica

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