Nanobeads-based rapid magnetic solid phase extraction of trace amounts of leuco-malachite green in Chinese major carps

Abstract

A proof-of-concept for the use of oleic acid coated magnetic nanobeads (OA-MNBs) for the magnetic solid phase extraction (MSPE) of trace amounts of leuco-malachite green (LMG) from fish samples was developed. The OA-MNBs were prepared by covalently conjugating oleic acid on amino-modified magnetic polystyrene beads. The OA-MNBs were characterized with transmission electron microscopy, Fourier transform infrared spectroscopy and zeta-potential analyzer. The optimized parameters for MSPE with OA-MNBs of LMG from fish muscle involved a combination of pH 10.0 in 10% acetonitrile, 1.5M sodium chloride as an adsorption solution, and an extraction procedure involving 6mg OA-MNBs in 18mL LMG adsorption solution. This was optimized for 0.5g fish muscles with an incubation period of 10min using 200μL acetonitrile for elution. Using the optimized parameters, the performance of MSPE with OA-MNBs was evaluated by analyzing LMG-spiked fish extracts with liquid chromatography-mass spectrometry (LC-MS/MS) method. The results indicated that recoveries of LMG (from 0.1 to 2ng/g) ranged from 71.2%–112.6% with relative standard deviations as low as 0.6%. Out of 57 field fish samples, eight LMG positive samples were confirmed using MSPE with OA-MNBs. Compared with traditional liquid–liquid extraction methods, the results showed that MSPE with OA-MNBs had a higher sensitivity for samples with low LMG concentration. Furthermore, the MSPE with OA-MNB took only 40min to perform without the need for time consuming sample-pretreatment process. Therefore, MSPE with OA-MNBs holds promise for rapid, sensitive, and cost effective screening for LMG in fish samples.