A new spectrophotometric method for the microdetermination of zinc is proposed. The method is based on complexation reaction of zinc(II) with the chromogenic agent 2,3-dichloro-6-(2-hydroxynaphthylazo)quinoxaline in the presence of cetyltrimethylammonium bromide (CTAB) and nonyl phenoxy polyetho-xyethanol (OP) in slightly basic medium containing 20% (v/v) ethanol. Under certain experimental conditions, Beer's law is obeyed over the range 0.02–0.80 µg ml of Zn with molar absorptivity of 1.06 × 10 l mol cm and Sandell sensitivity of 0.62 ng cm. The limits of detection and quantification as well as the regression equation are also calculated. The relative standard deviation for ten determinations for sample containing 0.5 µg ml was found to be 1.15%. As compared with other methods, our method is highly sensitive and selective because of the complex has high, and sharp absorption band at 616 nm. In addition, the present method is simple and rapid, no heating, no extraction or standing is needed. The proposed method has been applied successfully to the spectrophotometric determination of trace amounts of zinc in some alloys and ore samples. |
