A green cloud-point microextraction method for spectrophotometric determination of Ni(II) ions with 1-[(5-benzy1-1,3-thiazol-2-y1)diazenyl]naphthalene-2-ol

In this paper the efficiency of cloud point microextraction method has been confirmed by the preconcentration and spectrophotometric determination of nickel(II) ions with a new organic reagent 1-[(5-benzy1-1,3-thiazol-2yl)diazenyl]naphthalene-2-ol. The influence of several factors (the acidity of the media, the time of the reaction and heating, the type of extraction solvent used) on the interactions between Ni(II) and the azo dye was checked. Optimal conditions for carrying out the complexation reaction between the reagent and Ni(II) were established (absorbance maximum wavelength lambda(max) = 605 nm, time of heating the solution t(heat) = 10 min, the acidity pH(opt) = 5.5). Qualitative characteristics of the formed complex were calculated (epsilon(610) = 1.56 x 10(4) L-(1) cm(-1), Ig beta = 6.18). Two spectrophotometric methods of nickel(II) determination with the application of conventional liquid-liquid extraction and cloud-point microextraction were developed, and their main analytical characteristics were compared. The elaborated extraction technique with the application of cloud-point extraction and liquid-liquid microextraction provides significantly better performance characteristics for nickel determination (LOD = 3.9 mu g L-1, LOQ = 11.8 mu g L-1), and instead of 25 mL of toxic toluene, only 200 mu L. of ethylene glycol was used. The new method of Ni(II) determination was tested on model solutions and real samples. (C) 2017 Elsevier B.V. All rights reserved.