SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF Cu(II) AND Co(II) USING 5-BROMOSALICYLALDEHYDE THIOSEMICARBAZONE BY PARTIAL LEAST SQUARES REGRESSION METHOD

The simultaneous spectrophotometric method is described for the determination of Cu(II) and Co(II) by 5bromosalicylaldehyde thiosemicarbazone (5-BSAT) using partial least squares regression method. The ligand reacts with two ions to form greenish yellow and brown colored [Cu(II)–5-BSAT] and [Co(II)–(5-BSAT)2] complexes, respectively. The absorption peaks of these complexes were found overlapping at λmax of 378 nm and 381 nm, respectively. Formation of all of these complexes was complete within 20 min at pH 5.0. The linear ranges were 4.0×10 M – 9.6×10 M for Cu(II) and 8.0×10-6 M – 8.0×10-5 M for Co(II) with molar absorptivity, ε of 1.09×10 L.mol.cm and 1.42×10 L.mol.cm, respectively. Partial least squares (PLS) regression method is proposed for the simultaneous determination of these ions with the spectrophotometric absorbance data between wavelengths 370 and 446 nm at an interval of 4 nm. A training set was generated and its accuracy was tested in a test set. The test set garnered a root mean square error (RMSE) of 0.192 for copper and 0.489 for cobalt. The relatively small RMSE suggests only a small difference between predicted versus measured concentrations, demonstrating the accuracy of our model. The proposed method is successfully employed in the analysis of water sample for determining concentrations of copper and cobalt.