Extraction and determination of aflatoxins in rich-lipidic matrices using deep eutectic solvent as the extraction medium followed by UHPLC-FLD analysis

Since their identification in the 1960s, aflatoxins, as food contaminants,  have emerged as a significant public health concern, posing a formidable challenge to food quality control. The carcinogenic potential of these substances, coupled with their widespread presence in various food matrices, has led regulatory authorities to establish maximum permissible levels for these contaminants in such commodities. Traditional official methods have typically employed high amounts of methanol/water or acetonitrile/water solutions as extraction media, given the slightly polar nature of aflatoxins. Food matrices with high lipid content, such as pistachios (comprising about 40% of the total lipid fraction), usually necessitate multiple sample preparation steps before analysis. Specifically, a de-fatting step using hexane is commonly employed to diminish the presence of lipid-based interferents from the matrix.

A new approach has been devised, employing deep eutectic solvents (DES) as the extraction medium. This method reduces the overall quantity of organic solvent used and eliminates the need for the de-fatting step typically applied when dealing with lipid-rich matrices. Most DESs are characterized as non-toxic or less toxic and biodegradable. Given the intricate nature of extracts obtained from aflatoxin-contaminated pistachios, a subsequent purification and concentration step becomes imperative. The DES extracts are diluted with water and passed through a C18 solid-phase extraction cartridge. A minimal amount of methanol is used to elute the trapped aflatoxins, which are then injected into a high-performance liquid chromatography system coupled with a fluorescence detector. A partially porous C18 column is employed to effectively separate aflatoxins.
This innovative approach demonstrates the feasibility of using DES as an extraction medium for the challenging lipid-rich matrix of aflatoxin-contaminated pistachios. The greeness of the developed procedure was evaluated through two appropriate metrics, namely, AgreePrep and WhiteChemistry – RGB, showing better performance compared to official methods.