Heavy metals are indispensable for biological functions; however, they can also pose significant health risks when present in excess. Exposure through contaminated food and water can lead to a range of adverse health outcomes, including asthma and cancer. Therefore, accurate monitoring methods are of paramount importance for the prevention of such adverse effects. In response to this need, this study presents a new sustainable methodology by integrating liquid-phase microextraction (LPME) techniques with electrochemical processes to separate and concentrate target analytes (i.e. Cd, Cr, Cu, Fe, Ni, and Pb), followed by detection using inductively coupled plasma optical emission spectroscopy (ICP-OES). Specifically, electrochemically controlled liquid-liquid microextraction (EC-LLME) is employed to improve the extraction efficiency of heavy metals, while simultaneously reducing the consumption of reagents, waste production, and energy requirements. 

In this investigation, both hydrophilic and hydrophobic DES have been employed to extract target analytes in different food matrices such as tea samples or edible oil samples. On the one hand, the hydrophilic DES formed by choline chloride (ChCl) and ethylene glycol (EG) in a 1:2 molar ratio was used to extract heavy metals from edible oil samples. On the other hand, the hydrophobic DES synthetized by menthol (Men) and decanoic acid (Dec) in a 2:1 molar ratio was employed to carry out the extraction the analytes from tea samples.

The experimental factors influencing the EC-LLME procedure were optimized through multivariate analysis. Using the optimized parameters, the limits of detection (LOD) obtained with the developed method fall within the range of 0.09 to 2.8 µg kg-1. Additionally, recovery experiments were conducted in real edible oil and tea samples, to assess the trueness of the method. The recovery values obtained were between 86 and 109%.