Simultaneous spectrophotometric determination of calcium and magnesium in dialysis fluids using multivariate calibration methods

A method for simultaneous spectrophotometric determination of calcium and magnesium in dialysis fluids using multivariate calibration methods is proposed. The method is based on the development of the reaction between the analytes and Eriochrome Black T at pH 10.1. The parameters of chemometric procedure such as the spectral region and the number of factors were optimized. Three more convenient models of PCR, PLS-1 and PLS-2 were applied and the results were compared. A series of synthetic solutions containing different concentrations of calcium and magnesium were used to check the prediction ability of these chemometric methods. The optimum method was applied to the analysis of commercial dialysis fluids and the accuracy of proposed procedure was compared with that obtained by the USP reference method. These measurements carried out with good precision and RSD of real samples analysis (n=3) were found to be less than 1.85%. It was also observed that the presence of the other components frequently added to dosage forms caused no interference effect in the proposed method.