Enhanced fluorescence detection of ergosterol by hydrophobic fluorescent natural deep eutectic solvent

Abstract

Ergosterol (ERG) is a sterol found at high levels in cell membranes of fungi and is a smart option to be used as proof of fungal contamination in food samples. Therefore, the objective of this work was to develop a fast, sensitive and ecological methodology based on the use of hydrophobic fluorescent natural deep eutectic solvents (HPB-FLUODES) to determine ERG by fluorescence detection in edible mushrooms. The proposed approach involves a green sample preparation and a low cost instrumental technique leading to an efficient and simple analytical methodology suitable for high-throughput analysis (2.4 samples per minute). The experimental variables, such as the type of HPB-FLUODES, sample/solvent mass/volume ratio, time, and temperature of extraction were studied and optimized. The selected variables were HPB-FLUODES thymol:lactic acid 1:2, 2.5 mg of sample, 1 mL of HPB-FLUODES, and 45 min of extraction at 40°C. The LOD and LOQ were 0.09 µg g−1 and 0.29 µg g−1, respectively. The results show an enhancement of ERG fluorescence signal of 1825% against the ERG signal in methanol media. The present approach shows outstanding green performance using AGREE®, AGREEprep® and WAC principles. Finally, the analysis of edible mushrooms demonstrates the feasibility of the proposed green methodology.