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Guanidinium ionic liquid-based surfactant as adequate solvent to separate and preconcentrate cadmium and copper in waters using in-situ dispersive liquid–liquid microextraction

Abstract

An in-situ dispersive liquid-liquid microextraction (DLLME) method together with flame atomic absorption spectroscopy (FAAS) is developed for the extraction and determination of copper and cadmium from aqueous samples using as extractant solvent a low cytotoxic ionic liquid (IL)-based surfactant, specifically decylguanidinium chloride (C10Gu-Cl). The IL-based surfactant 1-hexadecyl-3-butylimidazolium bromide (C16C4Im-Br) is also used for comparative purposes. In the method, N,N´-bis(salicylidene)thiocarbohydrazide is the complexing agent, and the metathesis reaction in the in-situ DLLME is accomplished using lithium bis[(trifluoromethyl)sulfonyl]imide. Main parameters affecting the extraction efficiency of the method: pH of the sample, NaCl content, and vortex time, are properly optimized with a Doehlert experimental design. The method using C10Gu-Cl exhibited a limit of detection (LOD) four times lower and slightly better reproducibility than that of the imidazolium IL-based surfactant. The validation of the in-situ DLLME-FAAS method with C10Gu-Cl is accomplished for the simultaneous extraction and quantification of copper and cadmium from waters. The optimum method requires 10 mL of aqueous sample and ~25 µL of the IL-based surfactant to obtain a microdroplet of ~21 µL, which is diluted up to 120 µL with acetonitrile to perform the analytical determination of both metals. LODs down to 0.3 and 0.5 µg·L-1 were reached with the entire in situ IL-DLLME-FAAS for copper and cadmium, respectively. The inter-day relative standard deviation values were lower than 17% for both metals ions; with relative recoveries of 97.8% and 102%, and enrichment factors of 85 and 94, for copper and cadmium, respectively, at the low spiked level (4 and 6 µg·L-1, respectively). Furthermore, the developed method shows adequate precision and accuracy evaluated with a certified reference material, absence of matrix-effect, and high tolerance limits towards common cations (between 80 and 600) for the analysis of tap water, while accomplishing requirements of green analytical chemistry.

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Publication details

The article was received on 04 Jan 2018, accepted on 10 Feb 2018 and first published on 12 Feb 2018


Article type: Paper
DOI: 10.1039/C8AY00022K
Citation: Anal. Methods, 2018, Accepted Manuscript
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    Guanidinium ionic liquid-based surfactant as adequate solvent to separate and preconcentrate cadmium and copper in waters using in-situ dispersive liquid–liquid microextraction

    M. Khiat, I. Pacheco-Fernández, V. Pino, T. Benabdallah, J. H. Ayala and A. M. Afonso, Anal. Methods, 2018, Accepted Manuscript , DOI: 10.1039/C8AY00022K

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