Determination of cadmium in milk samples using deep eutectic solvent based liquid-liquid microextraction-graphite furnace atomic absorption spectrometry system

Abstract

Objective: This study aimed to improve the safety supervision of cadmium in milk samples. Methods: A liquid-liquid microextraction method based on hydrophobic deep eutectic solvent （DES） was developed for the determination of cadmium in milk samples by graphite furnace atomic absorption spectrometry. The types of deep eutectic solvents were selected for high extraction efficiencies and it was found that DES composed of thymol and lactic acid at the molar ratio of 1∶1 provided higher extraction efficiency. In addition, several important experimental conditions including the volume of DES, sample pH value, the pretreatment methods of samples were optimized. Results: Under the optimized conditions, Cd had good linearity in the range of 0~3.0 ng/mL, and the correlation coefficient was 0.998. The detection limit was 0.02 μg/kg. The recoveries ranged from 94.7% to 113.0% with relative standard deviations （RSD） of 0.38%~7.00%. Conclusion: With the advantages of simplicity, rapidness, exactness and low detection limit, this method could be used for the detection of cadmium in milk samples.

Keywords

• cadmium
• hydrophobic deep eutectic solvent
• liquid-liquid microextraction
• milk
• graphite furnace atomic absorption spectrometry