Determination of Erythromycin in Milk Samples by Nano Magnetite Hexadecylsilane by LC-Tandem Mass Spectrometry

Erythromycin is one of the typical macrolides, which is isolated by the Saccharopolyspora ‎erythraea. It has been listed in WHO essential medicine for improvement of the efficiency of ‎health system. In this study, magnetic iron nanoparticles were coated with cetyl as a non-polar ‎functional group and characterized by various techniques such as Infrared Spectroscopy, ‎thermal gravimetric analysis‎, scanning electron microscopy and vibrating sample ‎magnetometer. The as-prepared nanoparticles were used to extract erythromycin from the milk ‎samples. Separation was performed on a pentaflurophenyl column (150*2mm,3μm) using a ‎mobile phase consisting 70% acetonitrile and 30% ammonium acetate (10mM, pH3.5) with a ‎high performance liquid chromatography system coupled with tandem mass spectrometry‏.‏‎ The ‎separation was fast and completed in less than 5 minutes, under the optimized condition. Stable ‎isotope of erythromycin was used as internal standard in the sample preparation and calibration ‎curve. It was found that relative recovery of the method was 92.6%. The proposed method was ‎convenient and quick preparation method was achieved using external magnetic field without ‎centrifugation and filtration‏.‏‎ The detection limit and coefficient of determination were 2.4 ‎μg/L and R2 = 0.9983, respectively. The intra- and inter-day precisions of the proposed method ‎in different levels of spiked sample were in the range of 5.6-8.5% and 8.4-12.5%, respectively.‎