Ultrasound Assisted-Temperature Controlled Ionic Liquid Microextraction of Trace Copper and Silver after Chelation with Dithizone and Their Determination by Flame Atomic Absorption Spectrometry in Food and Water Samples

Abstract

Hydrophobic ionic liquid can be dispersed into infinite droplets in aqueous phase with sonication at 50°C, and then they can aggregate as large droplets at low temperature. Based on this phenomenon a new liquid-phase microextraction for preconcentration of copper and silver ions was developed. These ions were chelated by dithizone and extracted into the ionic liquid phase. 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 common ions in real samples had no obvious negative effect on the recovery of analytes. The proposed method had a good linearity in range of 10 - 100 ng mL−1 for both ions. For copper the precision at 20 ng mL−1 was 3.0% (RSD, n = 5) and the detection limit was 2 ng mL−1 and for silver the precision at 50 ng mL−1 was 2.9% (RSD, n = 5) and the detection limit was 1.2 ng mL−1. The method was applied to the analysis of food and water samples.