Sensitive elemental analysis of edible oil samples using a hydrophilic eutectic mixture as green solvent in...

Analyzing toxic metals in edible oils is crucial due to the associated health risks and strict regulatory limits. Traditional extraction methods are often time-consuming and require toxic solvents. Additionally, they are sometimes ineffective in complex oil matrices. Therefore, there is a strong demand for sustainable, efficient methodologies for extracting trace metals from oils. This study presents a green, effective approach to metal extraction from various edible oils using electrochemically enhanced microextraction.

We present a new, environmentally friendly, electrochemically enhanced liquid-liquid microextraction (EC-LLME) method that uses a choline chloride-based deep eutectic solvent (CC:EG, 1:2) to extract Cd, Cu, Fe, Ni, and Pb from various oil samples. We optimized the extraction parameters using a two-step experimental design. Under the optimal conditions of a 15 g sample, 315 μL of extractant, a 10 min extraction time, and a -0.75 V vs Ag pulse, the method achieved excellent linearity in the range of 5-500 μg kg^-1, high repeatability (CV ≤ 6 %), and low detection limits: 0.16 μg kg^-1 (Cd and Fe), 0.09 μg kg^-1 (Cu), 0.4 μg kg^-1 (Ni), and 1.5 μg kg^-1 (Pb). No analyte exceeded legal limits in the three samples studied (i.e., refined rapeseed oil, refined sunflower oil, and virgin olive oil), and recoveries in real and certified samples were nearly 100 %, confirming minimal matrix effects.

The EC-LLME method is a novel, sustainable alternative for extracting and quantifying trace metals in edible oils. Its superb analytical capabilities and eco-friendly safety, achieved by steering clear of noxious solvents, make it a suitable option for the identification of trace metals in edible vegetable oil samples.