Liquid-phase exfoliated 2D graphene nanoflakes electrochemical sensor coupled to molecularly imprinted polymers for the determination of citrinin in food

Abstract

Citrinin (CIT) is a mycotoxin produced as a secondary metabolite from different types of contaminating ubiquitous fungi, it can be produced mainly during post-harvesting treatments and storage, persisting until food is on market. Therefore, CIT represents a risk to health and business, and despite classical methods for the determination in foods, a lack of straightforward extraction/clean-up procedures and rapid and selective detection are evident.Herein, a rapid electrochemical strategy for CIT determination is proposed, the method relies on the use of graphene nanoflakes (GF) produced via a fast solvent-free water-phase exfoliation of graphite assisted by sodium cholate (GF-SC). The water-dispersed GF-SC nano-sized flakes were characterized and their use as a sensing layer in screen-printed electrodes was optimized. The GF-SC had a higher sensing ability for CIT compared to other carbon materials tested, allowing reproducible (RSD = 4.5%, n = 8) determination of CIT at levels below the maximum residual limit (LOD = 5 μg L−1) admitted in food. A molecularly imprinted polymer (MIP), produced with a fast sonochemical synthesis (5 min), was successfully used for the CIT selective extraction and clean-up from different samples i.e. red rice, blueberry, turmeric, corn, wheat germ, and rice starch. Reproducible (RSD <5.7%, n = 3) and accurate recoveries (85.8–111.4%) were obtained for all the samples, and a significant correlation with the CIT quantification performed with liquid chromatography/tandem mass spectrometry (LC-MS/MS) was achieved (relative errors: 9.9–9.1%), endorsing the usability of the proposed strategy.