Determination of ochratoxin A and citrinin in fruits using ultrasound-assisted solvent extraction followed by dispersive liquid-liquid microextraction with HPLC with fluorescence detection

A novel analytical method was developed for simultaneous determination of ochratoxin A and citrinin in fruit samples using ultrasound-assisted extraction (USAE) combined with dispersive liquid-liquid microextraction (DLLME), followed by high-performance liquid chromatography with fluorescence detection (FLD). Fruit samples were first extracted with 1% acetic acid in acetonitrile by USAE, and after centrifugation, the upper phase (acetonitrile) was used as the dispersant solvent in the subsequent DLLME step. CHCl3 was used as the extraction solvent in the DLLME procedure. The experimental parameters controlling the performance of DLLME (sodium chloride percentage, sample pH, and volume of extraction and disperser solvents) were optimized by means of an experimental design. To determine the presence of a matrix effect, calibration curves of standards and fortified fruit extracts (matrix matched calibration) were studied. Under optimum conditions, the mean recovery values of ochratoxin A and citrinin from three fruit samples were in the range of 75.0-103.0% (except for citrinin in apples), with relative standard deviations lower than 5.3%. Limits of detections (LODs) were in the range 0.06-0.16 mu g kg(-1). The proposed method was also applied for the analysis of ochratoxin A and citrinin in fifteen fruit samples purchased from markets in Guangzhou, China and no samples were contaminated with the two mycotoxins. The results show that UASE-DLLME combined with HPLC-FLD is a fast and simple method for determining ochratoxin A and citrinin in fruit samples.