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Zalov A. Z., Ibragimova S. A. Extraction-Photometric Determination of Cobalt (II) with Hydroxytiophenols and Hydrophobic Amines. Izvestiya of Saratov University. Chemistry. Biology. Ecology, 2019, vol. 19, iss. 4, pp. 379-386. DOI:

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Extraction-Photometric Determination of Cobalt (II) with Hydroxytiophenols and Hydrophobic Amines


The possibility of using hydroxythiophenols (HTP) for the photometric determination of cobalt (II) has been studied. Aminophenols (AP) were used as hydrophobic amine: 2- (N,N-methylamino methyl)-phenol (AP1) and 2- (N, N-methylaminomethyl) -4-methylphenol (AP2). Dichloroethane, chloroform and carbon tetrachloride turned out to be the best extractants. With a single extraction with chloroform, 97.5–99.5% of cobalt is recovered as a complex. The cobalt (II) complex is extracted into chloroform in the pH range of 3.6–6.3. Cobalt complexes with HTP and AR are stable in aqueous and organic solvents, do not decompose for two days and after extraction do not break down for more than a month. Maximum optical density is achieved within 5 minutes. The complex is stable when heated to 80° C. The results of studying the ratio Vaq / Vorg for extracting Co (II) in the form of a MLC showed that the optimum Vaq/Vorg is 5/5–80/5. The maximum analytical signal with the complex ation of cobalt with HTP and Am is observed at 540–565 nm. The molar absorption coefficient is (2.62–3.01)×104. The ratio of components in the complexes is Co: HTP: AP = 1:2:2. According to the Nazarenko method it has been established that the complexing form of cobalt is Co2+. At the same time, the number of hydrogen atoms displaced by them from one HTP molecule turned out to be 1. Extracts of cobalt complexes obey the basic law of light absorption at a concentration of 1.25–20 μg/ml. Based on the results of spectrophotometric studies of cobalt (II) with HTP and AP methods for determining cobalt in different objects have been developed.

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