Spectrophotometric determination of copper after separation by collection of its 5,7-dibromooxine complex on naphthalene

A new method by collection of copper complex with naphthalene was proposed for the spectrophotometric determination of trace amounts of copper. This method is based on the formation of a yellow complex which is quantitatively collected with naphthalene, the dissolution of the naphthalene mixture in dimethylformamide and on the absorbance measurement at 420 nm. The yellow solution follows Beer's law at 420 nm over the range of 5-90 μg of copper in 10 ml of dimethylformamide. The molar absorptivity is calculated to be 7.0xl03 l･mol-l･cm-l,the sensitivity 0.0091 μg of copper per ㎠ for the absorbance of 0.001. The mean absorbance of the 10 samples containing 50 μg of copper wsa 0.550 with a standard deviation of 2.8xlO-3 or relative standard deviation of 0.51%. The other factors such as wavelength, pH, amounts of reagent and naphthalene, digestion time, shaking time and standing time are studied