Ultrasound-assisted emulsification–microextraction and spectrophotometric determination of cobalt, nickel and copper after optimization based on Box-Behnken design and chemometrics methods

A fast, simple, and economical method for extraction, preconcentration and determination of cobalt, nickel and copper as their 1-(2-pyridilazo) 2-naphthol (PAN) complexes based on ultrasound-assisted emulsification–microextraction (USAEME) and multivariate calibration of spectrophotometric data is presented. Various parameters affecting the extraction efficiency were optimized both with univariate and Box–Behnken design. The resolution of ternary mixtures of these metallic ions was accomplished by using partial least-squares regression (PLS), orthogonal signal correction-partial least-squares regression (OSC-PLS), and orthogonal signal correction-genetic algorithmspartial least-squares regression (OSC-GA-PLS). Under the optimum conditions, the calibration graphs were linear in the range of 2.0–150.0, 2.0–120.0 and 2.0–150.0 ng mL⁻¹ for Co²⁺, Ni²⁺, and Cu²⁺, respectively, with a limit of detection of 0.14 (Co²⁺), 0.13 (Ni²⁺) and 0.14 ng mL⁻¹ (Cu²⁺) and the relative standard deviation was <2.5%. The method was successfully applied to the simultaneous determination of these cations in different samples.