Improved signals ratio resolution method by optimization of resolution function-simultaneous determination of Cu(II) and Cd(II) in water samples

From an ecological and economical point of view, it is important to design analytical procedures for monitoring heavy metals in the environment and in dustrial processes in a way to minimize the use of hazardous reagents and r educe the analysis time. In this paper, a well-known dithizonate extraction -based method for the determination of many metal ions was improved by usin g chemometrical selectivity of the strongly overlapped spectra of copper an d cadmium dithizonates in CCl4 for their simultaneous determination from a single extraction at pH 10. The individual absorption spectra, having absor ption maxima difference of only 20 nm, were separated, and the metal ions w ere quantified by using an improved procedure for optimizing the resolving function in a recently proposed signals ratio method. The procedure consist s of using many different resolving functions and plotting the difference o f the mean of absolute and nonabsolute mean values of pseudosignals [PDMMV (PS)] against analyte concentrations obtained with each of the resolving fu nctions, thus obtaining 2 straight lines having intersections that give a u nique and reliable value of the unknown concentration of the individual ana lyte in mixture giving strongly overlapped spectra, In this way, the main d rawback of the signals ratio resolution method, that is, the visual estimat ion of optimal resolving function, is eliminated. The proposed parameter, P DMMV (PS), was tested by using both simulated and experimental spectra. Cop per was determined in the mixture with ca 20-fold excess of cadmium, and ca dmium was determined in ca 10-fold excess of copper at submicromolar concen tration levels.