Establishment and validation of an acid alumina column clean-up for determination of trace citrinin in food samples

Citrinin (CIT) is frequent contamination of red fermented rice as a recognized public health threat. Although various quantitative techniques have been developed for CIT detection, most of these methods require expensive equipment and specially trained personnel. This study was aimed to develop an approach for cleaning up and purifying samples from complex matrix prior to CIT detection by high-performance liquid chromatography-fluorescence (HPLC-FLD). In order to achieve the optimal purification, the effects of 6 kind of traditional carrier adsorption materials and 7 types of eluents with different pH values on CIT recoveries were evaluated. Acidic alumina was finally selected as the optimal packed column for CIT clean-up. Methanol was used to remove the impurities after food extract was loaded on the acidic alumina column, and 80% methanol solution (pH 2.1) was used for CIT elution. Standard recovery test showed that the average recoveries for CIT-spiked samples after second elution was 91.46%, which was significantly higher than that of commercial immunoaffinity column. To examine the applicability of the proposed method, 29 kinds of food samples were treated with methanol and 80% methanol (pH 2.1) before HPLC analysis. Result showed that all samples tested positive for CIT, soy sauce and red fermented bean curd contained the highest levels of CIT contamination, indicating the feasibility of acidic alumina column with specific elution method. The proposed method would provide a new alternative approach for CIT enrichment, through a simple, reusable, cheap, and environmentally friendly solid-phase extraction procedure.