Ionic Liquid-Based Ultrasound-Assisted Emulsification Microextraction of Cadmium in Biological Samples: Optimization by a Multivariate Approach

An ionic liquid-based ultrasound-assisted emulsification microextraction method was developed for the preconcentration and determination of cadmium followed by flame atomic absorption spectrometry. Cadmium was complexed with 4-(2-pyridylazo) resorcinol, and then extracted into fine drops of 1-butyl-3-methylimidazolium hexafluorophosphate that served as the ionic liquid. The pH, ligand concentration, volume of ionic liquid, sonication time, and temperature were optimized by a multivariate technique. The results showed that concomitant ions did not affect the determination of cadmium. The detection limit and enhancement factor under the optimal conditions were 0.21 micrograms per liter and 92, respectively. The relative standard deviation of 10 micrograms per liter of cadmium was less than 5.0 percent. The validity of the method was investigated by the analysis of a spinach leaves standard reference material. The method was suitable for the preconcentration of cadmium in food and biological samples.