Determination of formaldehyde in shiitake mushroom by ionic liquid-based liquid-phase microextraction coupled with liquid chromatography

Using ionic liquid as extraction solvent and 2,4-dinitrophenylhydrazine (DNPH) as derivative agent, formaldehyde in shiitake mushroom was determined by liquid-phase microextraction coupled with high-performance liquid chromatography (HPLC). Shiitake mushroom was leached with water and filtrated, then the formaldehyde in filtrate was derivatized with DNPH and extracted simultaneously into a 10 μl drop of ionic liquid suspended on the tip of the microsyringe, and finally injected into the HPLC system for determination. The proposed procedure has a detection limit of 5 μg l−1 formaldehyde in extraction solution, thus the mushroom sample filtrate could be diluted with a large ratio to eliminate the influence of sample matrix. The method has a relative standard deviation of 3.5% between days for 53.5 μg l−1 formaldehyde standards. High contents of formaldehyde (119–494 μg g−1 wet weight), which is harmful for human beings, were detected in shiitake mushroom. Therefore, strategies must be taken to prevent the accumulation and strictly control the content of formaldehyde in shiitake mushroom.