Automated simultaneous determination of mercury and copper in edible oils by reversed-phase column-based extraction with deep eutectic solvent

In this study, a new automated method for the simultaneous determination of mercury and copper in edible oils using deep eutectic solvents and inductively coupled plasma optical emission spectrometry was developed and tested. The developed method uses a deep eutectic solvent consisting of choline chloride, thiourea and lactic acid to effectively extract mercury and copper from edible oil matrices. The extraction process involves automatically passing an oil sample through a microcolumn with the deep eutectic solvent retained as a stationary phase on glass fiber. This approach significantly reduces sample preparation time and improves reproducibility. The established LODs were 0.13 μg L⁻¹ for mercury and 0.12 μg L⁻¹ for copper, while the LOQs were 0.4 μg L⁻¹ and 0.36 μg L⁻¹, respectively. The method demonstrated high accuracy, with relative standard deviations for repeatability and inter-day reproducibility ranging from 2 % to 9 %. The extraction recovery of both metals exceeded 95 %, confirming the efficiency of the DES-based extraction process. An environmental assessment of the method using the AGREEprep tool showed a favorable environmental index of 0.63.