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-micro extraction (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 algorithms partial 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.