Simultaneous spectrophotometric determination of micro quantities of iron and aluminum

A fundamental study has been made of a spectrophotometric method for the simultaneous determination of micro quantities of iron and aluminum contained in very low concentration. A relatively large volume of acidified sample solution is taken, and treated with oxine solution and ammonium acetate solution to adjust the pH to 5.25.5. The resulting solution is transferred to a separatory funnel and the volume is brought to a definite and convenient one-for example, 200, 300, or 400 ml. Then iron and aluminum oxinates are extracted with exact 10 ml of chloroform; and by measuring the absorbancies of this dried chloroform solution at 470 and 390 mμ, these two metals are determined. In this case, care should be taken because the chloroform is slightly soluble in water and its volume after extraction decreases in proportion to the volume of aqueous solution from which extraction is made ; therefore, calibration curves must be prepared for every volume of aqueous solution. By this method, five micrograms each of both iron and aluminum present in about 400 ml of aqueous solution can be determined rapidly and accurately.