Simple and sensitive determination of nitroimidazole residues in honey using stir bar sorptive extraction with mixed mode monolith followed by liquid chromatography.

In the present study, we developed a simple and sensitive method for the simultaneous determination of metronidazole (MTZ), ronidazole (RNZ), dimetridazole (DMZ), and tinidazole (TNZ) in honey. Honey samples were diluted with water, then directly treated by stir bar sorptive extraction (SBSE) based on poly(methacrylic acid-3-sulfopropyl ester potassium salt-co-divinylbenzene) monolithic material. The analytes were analyzed by HPLC equipped with diode array detector. In the optimized process, several parameters, including the composition of desorption solvent, pH value and ionic strength in sample matrix, extraction, and desorption time, were investigated in detail. Under the optimized conditions, the detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target compounds were achieved within the range of 0.47-1.52 and 1.54-5.0 μg/kg from spiked honey sample, respectively. The calibration curves showed the linearity ranging from 2 to 200 μg/kg for dimetridazole and tinidazole, 5-200 μg/kg for metronidazole and ronidazole. Method repeatability presented as intra- and interday precisions were found with the RSDs <4.43 and 4.41%, respectively. Finally, the developed method was successfully applied to the determination of nitroimidazoles in different honey samples and satisfactory recoveries of spiked target compounds were in the range of 71.1-114%.