Electrochemically controlled liquid-liquid microextraction: an innovative methodology for heavy metal extraction from...

A growing concern about toxic metal contamination in food has generated a need for efficient, sustainable, and non-toxic sample preparation techniques. Conventional extraction methodologies frequently entail the utilization of hazardous solvents or exhibit a lack of sensitivity. There is an increasing demand for analytical methodologies that are more environmentally friendly and capable of extracting trace metals from complex matrices, such as tea. This study aims to address the need for an efficient and environmentally friendly method for the extraction of metals from tea samples using a combination of electrochemically assisted microextraction and a eutectic mixture as extractant.

An innovative electrochemically enhanced liquid-liquid microextraction technique has been developed, employing a green eutectic mixture composed of a menthol-based hydrophobic deep eutectic solvent (menthol:decanoic acid, 2:1) and a non-toxic ionic liquid (1-hexyl-3-methylimidazolium chloride) to enhance conductivity. The experimental conditions for the extraction procedure were optimized through the implementation of a design of experiments approach. In the context of optimal conditions (i.e., 10 g sample, 315 μL extractant, 5 min extraction, pH 4.66, 1 wt% 8-hydroxyquinoline, 600 rpm shaking and a single -0.75 V pulse vs. Ag), the method demonstrated excellent linearity, repeatability, and low limits of detection: 0.2, 0.2, 0.7, 2.8 and 0.5 μg kg^-1 for Cd, Cr, Ni, Pb and Zn, respectively. The recovery of real and certified tea samples approached 100 %, with negligible matrix effects. Furthermore, no analytes exceeded the maximum permissible limits established by legislation in the infused samples under study.

The proposed method represents a substantial advance in sustainable analytical chemistry, as it facilitates the efficient extraction of metals from tea without the use of toxic solvents. Its performance and environmental compatibility position it as a solid alternative for routine metal analysis in food safety monitoring.