Progressing an extraction method for enrichment of tetracyclines before their chromatografic determination

Many methods have been used for an antibiotic residue analysis in animal foods. In this study, two different dispersive liquid-liquid microextraction methods for enrichment of tetracyclines before high performance liquid chromatography determination in milk, egg and honey samples have been progressed. In the first method, traditional ionic liquid based dispersive liquid-liquid microextraction method has been developed. 1-Hexyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]imide as an ionic liquid was used. To increase extraction efficiency, pH, salt effect, volume of extractant solvent, type of dispersive solvent, volume of dispersive solvent, extraction time and centrifugation time were optimized. At optimized conditions, the enrichment factors of the studied six tetracycline antibiotics (minocycline, oxytetracycline, tetracycline, chlorotetracycline, methacycline, doxycycline) were found in the range of 15 to 105. The residue of tetracyclines were not found in the studied real samples. For the accuracy of the method, the 100 and 250 microgram per liter of standard tetracycline mixture solutions were spiked to the blank real milk, honey and egg samples and the percentage recovery was obtained betwwen 50 and 95. In the second method, in-situ ionic liquid based dispersive liquid-liquid microextraction method has been introduced for enrichment of four tetracycline antibiotics before chromatographic determination. 1-benzyl-3-methylimidazolium chloride was used as ionic liquid. To increase extraction efficiency, optimization parameters (volume of ammonium hexafluorophoshate salt solution, equilibrium time, centrifugation time, volume ratio of ionic liquid/salt) were investigated. At optimized conditions, enrichment factors of four tetracycline antibiotics (tetracycline, chlorotetracycline, methacycline, doxycycline) were found between 25 and 98. The residue of tetracyclines were not found in the studied real samples. For the accuracy of the method, the 50 and 250 microgram per liter of standard tetracycline mixture solutions were spiked to the blank real milk, honey and egg samples and the percentage recovery was obtained betwwen 65 and 120.