SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF CALCIUM AND MAGNESIUM IN MINERAL WATERS BY MEANS OF MULTIVARIATE PARTIAL LEAST-SQUARES REGRESSION

A method for simultaneous spectrophotometric determination of calcium and magnesium in mineral waters using multivariate calibration methods is proposed, The method is based on the development of the reaction b etween the analyses and Methylthymol Blue at pH 11, Two operational mo des were used: static (spectral information) and flow injection (FI) ( spectral and kinetic information), The selection of variables was stud ied. A series of synthetic solutions containing different concentratio ns of calcium and magnesium were used to check the prediction ability of the partial least-squares models, The method was applied to the ana lysis of mineral waters and the results were compared with those obtai ned by complexometry. No significant differences at the 95% confidence level were found, The proposed method is simple, accurate and reprodu cible, and it could be easily adapted as a portable (static mode) or a utomatic (FI) method.