THE APPLICATION OF PARTIAL LEAST-SQUARES METHOD (PLS) FOR SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF CALCIUM AND MAGNESIUM IN HUMAN SERUM

Application of a partial least squares algorithm (PLS-1) is proposed i n this work for simultaneous spectrophotometric determination of calci um and magnesium in human serum. Two chromogenic agents, Calmagite hyd roxy-4-methyl-2-phenylazo)-2-naphtol-4-sulfonic acid] and o-Cresolphta lein [3',3 ''-bis{[bis(carboxymethyl)amino]methyl}-5'5 ''-dimethylphen olphtalein] were used, which form color complexes with the two element s studied. As expected, significant interferences were observed for th e individual methods (Ca-o-Cresolphtalein and Mg-Calmagite) in the pre sence of the second metal. However, applying a full-spectrum chemometr ic method PLS-1, it was possible to eliminate these interferences in t he calibration step and satisfactory prediction results were obtained for calcium and magnesium in real serum samples. The proposed procedur e was validated using Refererence Serum (171760 Boehringer Mannheim, G ermany). The analytical results obtained for human serum were compared with the results of AAS determination.