Determination of aflatoxin M1 in liquid milk using high performance liquid chromatography with fluorescence detection after magnetic solid phase extraction
A new and sensitive method based on magnetic solid phase extraction (MSPE) with antibody-free modified magnetic nanoparticles (MMNPs) followed by high performance liquid chromatography with post-column derivatization and fluorescence detection (HPLC-PCD-FD) has been developed for the separation and determination of aflatoxin M1 (AFM1) in liquid milk. Magnetic nanoparticles coated with 3-(trimethoxysilyl)-1-propanthiol (TMSPT) and modified with ethylene glycol bis-mercaptoacetate (EGBMA) were used as the adsorbent. The usefulness of MMNPs has been previously validated as an antibody-free cleanup adsorbent. The experimental parameters affecting the extraction efficiency, such as pH, adsorption and desorption times, amount of adsorbent, and type and volume of desorption solvent, were investigated and optimized. Under optimum conditions, the calibration curve for AFM1 determination showed good linearity in the range of 0.015–10.0 μg L−1 (R2 = 0.9998), and the limit of detection (S/N = 3) was estimated to be 0.005 μg L−1. The intra-day and inter-day precision (RSD %) of AFM1 was in the range of 3.1–5.1%. Good spiked recoveries ranging from 91.2 to 102.2% were obtained. The results were compared with an official method based on conventional immunoaffinity columns (IAC), and it was determined that the developed method is simple, rapid, inexpensive, and accurate.