Competition coordination of copper in aluminium solution and determinationof the stability constant of their complexes with dibromomethyl dibromocarboxyazo

The reaction between copper (II) and dibromomethyl dibromocarboxyazo (DBMDB CA) was used for determination of copper in the presence of a large amount of Al(III). The concept of selective competition coordination (SCC) is prop osed and applied here. A spectroscopic correction technique was also used i nstead of ordinary spectrophotometry so that the stability constants of Cu and Al complexes could be determined easily. Results showed that AI(DBMDBCA ), and Cu(DBMDBCA)(2) complexes were formed. Their cumulative stability con stants are 5.85 x 10(9) and 2.36 x 10(11), respectively, whereas their abso rptivities are 1.41 x 10(4) l.mol(-1)cm(-1) at 610 nm and 4.56 x 10(4) l.mo l(-1)cm(-1) at 530 nm, respectively. The method is selective and sensitive for the determination of copper. Its relative standard deviation (RSD) is 3 .6% (n=6) and its recovery rate is between 96.4 and 102%.