Development of N and S doped carbon sorbent-based dispersive micro solid phase extraction method combined with dispersive liquid-liquid microextraction for selected mycotoxins from soymilk samples

A carbon-based dispersive micro solid-phase extraction method was combined with dispersive liquid-liquid microextraction for the simultaneous extraction of five mycotoxins form soymilk samples. The analytes determination was done by high-performance liquid chromatography-fluorescence detection. The sorbent was synthesized by a simple hydrothermal method. At the beginning of the process, the soymilk sample transferred into a glass test tube and then 250 mg trichloroacetic acid was added into the solution to precipitate its proteins. After vortexing and centrifugation, the obtained upper phase was removed and the dispersive micro solid-phase extraction method was performed on it. The analytes were eluted with a proper organic solvent to use in the following dispersive liquid-liquid microextraction method. Optimization and validation of the method were done based on one-variable-at-a-time strategy and International Council Harmonization guideline, respectively. Under final conditions low limits of detection and quantification in the ranges of 0.13-0.83 and 0.43-2.7 ng/L were obtained, respectively. Also, intra- (n = 6) and inter-day (n = 4) precisions were obtained in the range of 4.7-7.6 % at a concentration of 3 ng/L of each analyte which showed an acceptable repeatability. Finally, the proposed method was performed on different soymilk samples marketed in Tabriz city and aflatoxin B1 was found in all samples. One soymilk was contaminated by ochratoxin A.

Automated summary

The study developed a combined method of dispersive micro solid-phase extraction and dispersive liquid-liquid microextraction for the simultaneous extraction of five mycotoxins in soymilk samples. The method showed low limits of detection and quantification, with acceptable repeatability in analyzing different samples from the market. The proposed approach successfully detected aflatoxin B1 in all tested samples and ochratoxin A in one sample.