Copper is quantitatively retained by 1,10-phenanthroline and tetraphenylborate onto benzophenone in the pH range 1.6-10.4 from a large volume of aqueous solutions of various samples. After filtration, the soil mass consisting of copper complex and benzophenone was dissolved in 5 mL of dimethylformamide and the metal was determined by flame atomic absorption spectrometric. About 0.2 mug of copper can be concentrated from 500 mL of aqueous sample, where its concentration is as low as 0.4 ng/mL. Eight replicate determinations of 3.0 mug/mL of copper in final dimethylformamide solution gave a mean absorbance of 0.180 with a relative standard deviation of 1.8%. The sensitivity for 1% absorption was 73 ng/mL. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of copper in various alloys and biological samples.