Analytical applications of ternary complexes-II Spectrophotometric determination of copper as rose bengal bisphenanthrolinium copper(II)

A ternary complex system, [(Cu.phen(2))Rose Bengal], is proposed for the determination of traces of copper ion. The reaction is rendered specific for copper amongst 56 cations and most anions by extraction of bis(2,9-dimethyl-1,10-phenanthrolinium) copper(I) from an EDTA medium. Because of the high molar absorptivity, 62,500, solutions containing 0.002 ppm of copper may be analysed without difficulty. The colour system is stable for a period of days.