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The Schiff base of salicylaldehyde and aminopyridines as highly sensitive analytical reagents

The analytical applicability of heteroaromatic Schiff bases, 2-(3-pyridylmethyliminomethyl)phenol (componud 1), 2-(2-pyridylimionmethyl)phenol (componud) 2), 2-(2-amino-3-pyridylimionemethyl)phenol (componud 3), N,N´-bis(salicyldene)-2,6-pyridinediamine (componud 5) and 2-(2-amino-4-methox-ymethyl-6-methyl-3-pyridylmethylimionmethyl)phenol (componud 6), was proved. The invewstigation included a study of the characteristics that are essential for solvent extraction and for the spectrophotometric and spectrofluorimetric determinations of copper. Despite structural similarities, the investigated Schiff bases exhibited different behaviour in solution. Componuds 2-5 adopted predominatly the enolimino form in most solvents, whereas compound 1 was partially present as keotamine in the solutions of polar solvent. Compound 6 was found to be the tautometric mixture of cyclic diamine and enolimine in most solvents. All the investigated Schiff bases were capable of quantitatively extracting transition metals ingo chloroform. In the case of Cu(II), componud 4 proved to be an effective extractant in thje range 5<pH<12, compounds 1 and 6 were effective in the range 6<pH<12, wheraer componuds 2, 3 and 5 were effective only tn the alkaline medium above pH 9. The spectropohotometric determination of Cu(II) after extraction was very sensitive and selective with regard to Cd(II) and Pb(II). Highest sensitivity was achived with compound 4 (?430=2.1x104 mol-1 1 cm-1). This characteristic was favourable compared to other well-known copper reagents. Since the flouroscence of Schiff bases was quenched by Cu(II), Mn(II), Fe(III), Ni(II) and Cr(III), the sensitivity as well as the selectivity were further enhanced using the spectrofluorimetric procedure. Additional advantges of these compounds to other reagents for copper(II) are simple preparation and a detailed knowledge of their equilibria.

Schiff bases; Salicylaldehyde; Copper; Spectrophotometric method

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