Combination of cold-induced aggregation microextraction and central composite design for preconcentration and determination of copper in food and water samples

Abstract

Abstract An efficient, simple, and rapid cold-induced aggregation microextraction method was applied to preconcentrate copper (II) ions from water and food samples as a prior step to its determination by flame atomic absorption spectrometry. In this method, small amounts of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF6] and 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [Hmim][Tf2N] as hydrophobic ionic liquids (ILs) and extractant solvents were dissolved in the sample solution containing Triton X-114. After dissolving, the solution was cooled in an ice bath and a cloudy solution was formed of IL fine droplets due to the decrease of IL solubility. The effective parameters, such as pH, amount of chelating agent and IL, temperature, and concentration of salt were optimized by a fractional factorial design to identify the most important parameters and their interactions, and central composite methodology was used to achieve the optimum point of effective parameters to the respon...