Ultrasouned assisted-temprature controlled ionic liquid microextraction procedure combined with flame atomic absorption spectrometry for determination of trace copper in food samples

Hydrophobic ionic liquid could be dispersed into infinite droplets in aquase phase with sonication at high temperature (50oC), and then they can aggregate as big droplets at low temperature[1]. Based on this phenomenon a new liquid-phase microextraction for the preconcentration of copper was developed. In this experiment, copper was complexed using dithizone as chelating agent, and then entered into the infinite ionic liquid droplets. After cooled with ice-water bath and centrifuged, copper complex was enriched in the ionic liquid droplets. Important parameters affected the extraction efficiency including pH, amount of chelating agent, volume of ionic liquid, extraction time, centrifugation time, and temperature have been investigated. The interference study showed that the usually coexisting ions containing in samples had no obvious negative effect on the recovery of copper. The experimental results indicated that the proposed method had a good linearity (R2 = 0.9945) from 10 to 100 ngmL−1. The precision at 20 ngmL−1 was 2.99% (RSD, n = 3) and the detection limit was 2 ngmL−1. This novel method was validated by determination of copper in four real samples for the applicability and the results showed that the proposed method was very good for the future use and the recoveries were in the range of 98.5-100%.