Preconcentration and determination of four antibiotics in biological samples using nanofluid-assisted magnetic dispersive micro-solid-phase extraction coupled with high-performance liquid chromatography

A sensitive and straightforward magnetic dispersive micro-solid-phase extraction as a sample preparation procedure coupled with high-performance liquid chromatography was developed to preconcentrate and clean up four antibiotics, including azithromycin (AZI), doxycycline (DOX), amoxicillin (AMO), and tetracycline (TC), from biological samples. For this purpose, several nanofluids with a magnetic colloidal gel structure were prepared based on the dispersion of three synthetic nanoparticles in dimethylformamide in the presence of an ionic liquid individually. The nanofluid preparation leads to a reduction in the extraction and desorption time and sorbent consumption through an increase in the sorbent surface area. Usage of the nanofluid can also increase the sorbent dispersion efficiency without using a dispersion agent. The ability of the magnetic colloidal gels to simultaneously extract the antibiotics was compared together. An experimental design including screening and optimization steps was utilized to optimize effective factors in the micro-extraction method. Under the optimum condition, the proposed method has linearity in the concentration ranges of 0.01-12.0, 0.01-12.0, 0.01-15.0, 0.05-15.0 ng mL(-1) with a determination coefficient (R-2) of 0.9940, 0.9951, 0.9939, and 0.9946, for the determination of AZI, DOX, AMO, and TC in water samples, respectively. LODs and LOQs were in the range of 0.003-0.015 and 0.01-0.05 ng mL(-1) to determine the analytes, respectively. Intra-day RSDs of the method (n = 5) for the determination of AZI, DOX, AMO, and TC with a concentration of 1.0 ng mL(-1) in water samples were 3.63, 3.49, 3.91, and 3.50%, respectively. Analysis of real samples such as urine and hair samples indicated that the proposed method has proper recoveries in the range of 86.0-101.4% with a relative standard deviation in the range of 3.76-5.36%.