Study On Aqueous Two-phase Extraction Of Antibiotics And Herbicides In Foods

In recent years, food safety has always been one of the major threats for humanbeings. Antibiotics used in beekeeping to prevent and cure bacterial diseases maypersist at trace levels in honey, being a potential risk to honey consumers in terms ofpossible allergic reactions, liver damage, yellowing of teeth, gastro-intestinaldisturbance, aplastic anemia and the development of bacterial resistance. Theintensive application of triazines has resulted in the contamination of atmosphere,water and agricultural products. Milk-producing animals may accumulate residues oftriazines through contaminated feed. Consequently, triazines may persist at tracelevels in milk. For those who often drink milk, the chance of them having cancer,birth defects and interruption of hormone functions is relatively high. Therefore,reliable analytical techniques are increasingly demanded to detect antibiotics andherbicides in foods.Aqueous two-phase system was first developed for separation and enrichment ofantibiotics and herbicides in foods. Then high-performance liquid chromatographywas applied to the determination of antibiotics and herbicides. By mixing cationic andanionic surfactants or the salting-out effect, homogeneous system was separated intotwo immiscible phases, forming aqueous two-phase system. Target analytes wereextracted into one of the phases according to the distribution coefficients of them inthe two phases, which was referred to as the aqueous two-phase extraction. Two typesof aqueous two-phase systems were applied to the extraction of antibiotics in honeyand herbicides in milk, respectively. The present methods are simple, fast, robust,green, low-cost and suitable for pretreatment of batch samples.An ionic liquid-anionic surfactant based aqueous two-phase system was developed and applied to the extraction of tetracycline, oxytetracycline andchloramphenicol in honey. The honey sample was mixed with Na2EDTA aqueoussolution. The sodium dodecyl sulfate, ionic liquid1-octyl-3-methylimidazoliumbromide and sodium chloride were added in the mixture. After the resulting mixturewas ultrasonically shaken and centrifuged, the aqueous two phase system was formedand analytes were extracted into the upper phase. The parameters affecting theextraction efficiency, such as the volume of ionic liquid, the category and amount ofsalts, sample pH value, extraction time, temperature, were investigated. The limits ofdetection of tetracycline, oxytetracycline and chloramphenicol were5.8,8.2,4.2μgkg-1, respectively. When the present method was applied to the analysis of real honeysamples, the recoveries of analytes ranged from85.5to110.9%and relative standarddeviations were lower than6.9%.A simple extraction method based on acetonitrile-K2HPO4aqueous two-phasesystem was developed for separation and enrichment of five triazines in milk samples.Acetonitrile was used for extraction of analytes from milk sample and precipitation ofmilk protein. Deproteinization and extraction were achieved in single step. Analyteswere extracted into the upper phase of the aqueous two-phase system. The parametersaffecting the extraction efficiency, such as the volume of acetonitrile, the type andamount of salts, pH value of sample, extraction time, were investigated. The limits ofdetection of atraton, desmetryn, atrazine, terbumeton and terbuthylazine were2.1,2.6,2.3,2.8,2.5μg L-1, respectively. When the present method was applied to the analysisof real milk samples, the recoveries of analytes ranged from86.3to120.6%andrelative standard deviations were lower than7.9%.