Microwave and SPE: a recipe for faster and greener lipid analysis

The analysis of sterols is performed on a daily basis in many laboratories as they serve as key markers for detecting adulteration in extra virgin olive oil (EVOO). Due to its high nutritional and economic value, EVOO is frequently targeted for fraud, often through mixing with cheaper oils. Accurately assessing the sterol profile is crucial for maintaining product authenticity and ensuring compliance with regulatory standards.
Traditionally, sterol fraction analysis requires multiple steps, including saponification, liquid-liquid extraction, thin-layer chromatography (TLC), and gas chromatography with a flame ionization detector (GC-FID). Although effective, this method has notable drawbacks: it is time-consuming (about eight hours), relies on large volumes of organic solvents, and demands intensive manual handling. These limitations reduce its suitability for high-throughput analyses and raise environmental concerns, as it conflicts with the principles of green analytical chemistry.
To overcome these challenges, this study developed a more efficient approach by combining the traditionally separate steps of saponification and liquid-liquid extraction into a single, integrated microwave-assisted saponification and extraction (MASE) step. This approach not only reduces processing time but also minimizes solvent consumption and waste generation.
Additionally, the solid-phase extraction (SPE) purification phase was optimized to further enhance efficiency and sustainability. By modifying the solvent mixtures and reducing the number of fractionation steps, the method achieved improved separation of sterols while lowering solvent use. The optimized approach demonstrated comparable analytical reliability to the official method, with no significant differences observed.
Moreover, its environmental impact was evaluated using the AgreePrep software, yielding an higher score than the score of the traditional method. Overall, the proposed method is faster (about 2 hours), more sustainable, and equally reliable for detecting sterol adulteration in olive oil. Its reduced analysis time and lower environmental footprint make it a valuable alternative for routine laboratory use, supporting quality control and regulatory compliance while aligning with green chemistry principles.