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Ternary ion-association complexes of cobalt with 4-(2-pyridylazo)resorcinol and tetrazolium salts

Vanya Dimitrova Lekova, Vidka Vasileva Divarova, Petya Vasileva Racheva, Kirila Trifonova Stojnova, Atanas Nikolov Dimitrov


The formation of ternary ion-association complexes of Co(II) with 4-(2-pyridylazo)resorcinol (PAR) and tetrazolium salts (TS) (3-(4,5-dimethylThiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride (TV) wereinvestigatedwith the aid of the extraction-spectrophotometric method. The optimum conditions for the extraction of Co(II) were found. On the basis of the experimental data and their mathematical treatment the association process in aqueous phase and extraction process was investigated quantitatively. The molar ratios of the components in the associates weredetermined. The results show that the extracted species could be represented with the general formula (TS)[CoH(PAR)2]. The following key constants were calculated: association constant, distribution constant, extraction constant and recovery factor.The validity of Beer’s law was checked and some analytical characteristics were calculated.


Cobalt-PAR chelate; tetrazolium salts; ion-association complexes; spectrophotometry; extraction

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