USE OF BETA-CORRECTION SPECTROPHOTOMETRY TO IMPROVE THE DETERMINATIONOF COPPER SOLUTION WITH ERIOCHROME BLACK-T

Copper has been determined by beta-correction spectrophotometry with e riochrome black T (EBT). This reaction is selective in the presence of EDTA to mask other metal ions. A non-ionic surfactant, polyethylenegl ycol n-octanoic phenylether (emulsifying agent, OP), was found to incr ease the sensitivity. The beta-correction method can completely elimin ate the effect of excess EBT in its Cu-II colored solution to give out the real absorpance of chelate produced. The sensitivity, precision a nd accuracy are increased. By means of the beta-correction principle, the complex ratio of Cu-II to EBT can be calculated as 1/2. Beer's law is obeyed over the range 0-2.0 mg l(-1) copper at 550 nm and the true molar absorptivity of Cu-EBT chelate equals 2.61 x 10(4) l mol(-1) cm (-1). The detection limit of copper is 0.03 mg l(-1) and the results s how that the relative standard deviation was less than 4.5% with the r ecovery between 92.0 and 109%.