Application of a new extraction method coupled to high performance liquid chromatography for tetracyclines monitoring in cow milk

Excessive use of antibiotics in the production of livestock has led to the accumulation of antibiotic residues in various livestock products such as meat and milk. Consumption of foods containing antibiotics leads to problems such as increased antibiotic resistance, while their accumulation in the body can lead to mutagenesis and cancers, liver damage and abortion. For this reason, monitoring residual antibiotics, especially in high-consumption and beneficial food products such as milk and dairy products, is of particular importance. In this research, a dispersive solid-phase micro-extraction method for the extraction of tetracycline, oxytetracycline, chlortetracycline and doxycycline antibiotics from 50 milk samples and their quantitative measurement by HPLC was developed. For this purpose, the effect of various parameters affecting the extraction efficiency such as the volume of the precipitating agent, the type and amount of solid adsorbent, ionic strength, aeration time and flow rate, type and amount of surfactant and type and volume of elution solvent were optimized. The results showed that all milk samples contained tetracycline residue and its concentration varied in the range of 146 to 319 ng / ml. No other antibiotics were found in the samples. The advantages of the proposed extraction method include high separation power and the possibility of analyzing a mixture of highly sensitive analytes, so that under optimal conditions, recoveries of the proposed method ranging from 80 to 91%, the LOD were in the range of 0.17-0.33 ng / ml and the linear range was in the range of 0.63-2000 ng / ml.