Dispersive liquid-liquid microextraction followed by magnetic nanoparticles retrieval of extract for separation and preconcentration of tetracycline from real samples before its selective spectrophotometric determination based on azo dye formation

A sensitive and selective method is reported for the determination of the low amount of tetracycline in real samples. The tetracycline is extracted and preconcentrated by dispersive liquid-liquid microextraction followed by retrieval of the extract with magnetic solid-phase extraction. The extracted analyte is determined by a selective spectrophotometric method based on the formation of a water-soluble violet mono azo dye between the tetracycline and diazotized p-nitroaniline in the basic medium. The dispersive liquid-liquid microextraction was performed using acetonitrile as the disperser solvent and 1-octanol as the extracting solvent. The extracted tetracycline in the dispersive liquid-liquid microextraction step was retrieved by dispersed hydrophobic oleic-acid-modified Fe3O4 magnetic nanoparticles. Thus, the method enjoyed the high surface area and strong magnetism properties of these nanoparticles avoiding the time-consuming centrifugation or column-passing processes. Finally, the tetracycline was eluted from the magnetic solid phase into 0.5 ml of ethanol, and coupled with diazotized p-nitroaniline in the basic medium for spectrophotometric quantification. Under the optimum conditions, good linearity (in the range of 7.6-650.0 mu g/L with R-2 = 0.9987), low detection limit (2.3 mu g/L), and preconcentration factor of 30.0 were obtained. The proposed method was successively applied to the determination of tetracycline in different samples.