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Kulichenko, S. A.; Doroshchuk, V. A.

doi:10.1023/a:1026332230205

Cited by 4 publications

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“…This is explained by the low distribution coefficients of the acids in the water-nonionic surfactant phase system [7]. When moderately hydrophobic acids with 5 ≤ n ≤ 9 are used, the recovery of cadmium into the nonionic surfactant phase increases monotonically with an increase in the length of their hydrocarbon radical.…”

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confidence: 99%

“…The advantages of micellar extraction are high absolute preconcentration coefficients for small sample volumes (50-100 mL); easy combination with chromatographic, spectroscopic, electrochemical, and other methods; improved performance characteristics; and a relatively low toxicity of the surfactants used [4][5][6]. In addition, the method is suitable for the effective and selective extraction of hydrophilic and hydrophobic compounds [7].The solubility of nonionic surfactants in water is due to the formation of hydrogen bonds between the oxygen atoms of the surfactant polyoxyethylene chain and water molecules [8]. When aqueous solutions of nonionic surfactants are heated above a specific temperature (cloud point, T c ), these bonds brake and phase separation occurs in the system.…”

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Preconcentration of Cadmium with OP-10 Nonionic Surfactant Phases at the Cloud Point

Doroshchuk

Kulichenko

2005

J Anal Chem

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The micellar extraction of microcomponents with nonionic surfactant phases at the cloud point is one of the most promising analytical applications of organized surfactant media [1,2]. Extraction with nonionic surfactant phases is used for the preconcentration and separation of metal ions, organic toxicants, and biologically active compounds [3]. The advantages of micellar extraction are high absolute preconcentration coefficients for small sample volumes (50-100 mL); easy combination with chromatographic, spectroscopic, electrochemical, and other methods; improved performance characteristics; and a relatively low toxicity of the surfactants used [4][5][6]. In addition, the method is suitable for the effective and selective extraction of hydrophilic and hydrophobic compounds [7].The solubility of nonionic surfactants in water is due to the formation of hydrogen bonds between the oxygen atoms of the surfactant polyoxyethylene chain and water molecules [8]. When aqueous solutions of nonionic surfactants are heated above a specific temperature (cloud point, T c ), these bonds brake and phase separation occurs in the system. As a result, two phases are formed: the micellar phase of a nonionic surfactant composed of coarse hydrated micelles and the aqueous micellar solution of the same surfactant with the concentration close to critical micellation concentration. The micellar phase is used for the preconcentration of microcomponents.Aliphatic monocarboxylic acids and their derivatives are universal extractants; they were proposed for the preconcentration and separation of many metals, including cadmium, a typical anthropogenic environmental pollutant [9,10]. Carboxylic acids are characterized by a high extraction capacity due to their good solubility in organic solvents [10]. This property persists in the micellar solutions of nonionic surfactants [11]. The aim of this work was to study the extraction of cadmium with carboxylic acids into nonionic surfactant phases and to select conditions for its atomic absorption determination in natural and waste waters using micellar-extraction preconcentration. EXPERIMENTAL Reagents and apparatus.Polyoxyethylated alkylphenol OP-10 (Fine Organic Synthesis Plant, IvanoFrankovsk) with the average molecular weight of 647 g/mol, concentration of organic substance >99%, and the average degree of oxyethylation n = 10-12 [12] was used. OP-10 was selected, because it forms a compact and highly viscous nonionic surfactant phase upon heating and the phase formation proceeds more rapidly than that for other nonionic surfactants. OP-10 solutions were prepared by dissolving its portions in distilled water. C n H 2 n + 1 -C 6 H 4 -O-(C 2 H 4 O) m -H ( m = 10-12, n = 8-10).Fatty monocarboxylic acids of the general formula C n H 2 n + 1 COOH of analytical and reagent grade (for liquid and solid acids, respectively) were used. Solid acids were additionally purified by recrystallization from water-ethanol mixtures. Working solutions of acids were prepared by dissolving acid portions in aqueous solut...

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