Determination of Traca Cu~(2+) in Zinc Electroplating Bath by Fading Spectrophotometry of Parafuchsin

A new method usable for the determination of Cu2+ was established with respect to the catalysis of Cu2+ for the fading oxidation of parafuchsin by hydrogen peroxide in boiling water.The feasibility of the newly established method in determination of trace Cu2+ in the bath for electroplating zinc was explored.It was found that at a maximum absorbance wavelength of 540 nm,Bill's law was abided by in terms of the adsorption of Cu2+ in the zinc-electroplating bath,within Cu2+ concentration range of 0～5 μg/mL.The apparent molar absorptivity was determined to be 4.038×105 L/(mol·cm),and the detection limit for Cu2+ was 1.2 μg/mL.In general,the method could be readily applied to the determination of Cu2+ in zinc-electroplating bath with satisfaction.