Application of a modified lighter than water organic solvent-based air-assisted liquid–liquid microextraction method for the efficient extraction of aflatoxin M1 in unpasteurized milk samples

Abstract

ABSTRACT An efficient analytical method has been developed for the extraction and quantification of aflatoxin M1 in milk samples using a modified air-assisted liquid-liquid microextraction method combined with high-performance liquid chromatography-fluorescence detector. Firstly, defatted milk is transferred into a glass test tube and its proteins are participated with zinc acetate solution. After vortexing and centrifugation of the mixture, the obtained supernatant is removed and transferred into a conical bottom glass test tube. Then, the adsorbed analyte onto the precipitated proteins is eluted with acetonitrile and after centrifugation, the eluant is mixed with the supernatant obtained from the previous step. A few microlitres of toluene (as an extraction solvent) is added into the solution and the mixture is sucked into a glass syringe and pushed out in the tube for four times. The obtained cloudy solution is centrifuged to collect the extraction solvent. Then, the lower aqueous phase is withdrawn by a glass syringe to transfer the extraction solvent to the conical section of the tube. The method was validated and under optimal conditions, it was found that the method has low limits of detection (0.9 ng L−1) and quantification (3 ng L–1), good linearity (r2 = 0.9976), and satisfactory repeatability (relative standard deviation ≤9% for intra- (n = 8) and inter-day (n = 6) precisions). The extraction recovery and enrichment factor of AFM1 were 87% and 87, respectively. Finally, the proposed method was applied on different milk samples and concentration of aflatoxin M1 was determined in the studied samples.