Application of multicomponent spectrophotometry in analysis of copper electroplating bath solutions

Multiwavelength multicomponent analysis for copper and nickel is explored within the spectral range 230-900 nm in order to enable copper (?0.2 g l^?1) and nickel to be determined simultaneously even at high (20 l^?1) and nickel concentrations in industrial electroplating baths. Calibration based on pure-component spectra is compared to multivariate calibration based on data reduction with principal component analysis with the partial least-square algorithm. By use of multivariate calibration techniques, sulphuric acid can also be determined indirectly by its effect on the absorbance of the metal ions. The performance of the method is evaluated for different spectral ranges and the experimental results are related to the selectivity of the different systems quantified by the condition number of the actual absorptivity matrix.