Spectrophotometric studies of the reaction of zinc(II) with some azo-triazol compounds and its application to the spectrophotometric determination of microamounts of zinc(II)

摘要

A new, simple, and sensitive quantitative spectrophotometric method for the rapid determination of zinc(II) using six azo compounds based on 3-amino-1,2,4-triazole, namely {3-(2,4-dihydroxy-1-phenylazo)-1,2,4-triazole) (I), 3-(2-hydroxy-5methyl- 1-phenylazo)-1,2,4-triazole)(II),3-(2-hydroxy-5-acetyl-1-phenylazo)-1,2,4-triazole)(III), 3-(2-hydroxy-5-ethylcarboxylate-1-phenylazo)-1,2,4-triazole)(IV), 3-(2-hydroxy-5-formyl-1-phenylazo)-1,2,4-triazole)(V),and 3-(2-hydroxy-5-bromo1-phenylazo)- 1,2,4-triazole) (VI), has been developed for use in aqueous media containing 40% (v/v) methanol. Linear calibration graphs are obtained up to 2.6, 5.9, 5.2, 5.2, 8.2 and 9.0 mu g mL(-1) using ligands I, II, III, IV, V, and VI, respectively. Absorption maxima, molar absorptivities, and Sandell's sensitivities of 1: 2 ( M: L) complexes were found to be 490, 530, 505, 520, 550, and 510 nm, 4.86 x 10 4, 2.10 x 10(4), 1.26 x 10(4), 0.10 x 10(4), 0.19 x 10(4), and 0.29 x 10 4 L mol(-1) cm(-1), and 0.0014, 0.0031, 0.0052, 0.0662, 0.0348, and 0.0225 mu g cm(-1) for ligands I, II, III, IV, V, and VI, respectively. Using the masking agents, the color reactions are free from interference by more than 30 ions investigated. The method has been applied to the spectrophotometric determination of trace amounts of zinc in pharmaceutical formulations and human hair samples. A study of some zinc solid complexes showed that chelation takes place through one nitrogen atom of the azo group and proton displacement from the hydroxyl group.