Determination Of Veterinary Drug Residues In Animal-Derived Products By Methanol Salting-Out Extraction

With the improvement of people's living standards,while focusing on strengthening nutrition,food safety testing is particularly important.At present,there is a phenomenon that the level of sample pretreatment technology lags significantly behind the development level of instruments.The development of balanced sample pretreatment technology is the key to analysis and detection.The paper summarizes the commonly used sample preparation techniques and detection methods,and combines fluorescence quenching technology and equilibrium dialysis method to study the binding of proteins to different drug molecules.On this basis,the method of methanol salting-out extraction was used to rapidly detect thiazolidine and florfenicol in four kinds of tetracyclines?TCs?,six sulfonamides?SAs?,and beef samples in animal-derived foods.The rapid detection of nitrobenzene drugs in aquatic products was established by using aqueous solution of organic solvent as extractant combined with high performance liquid chromatography.The paper is divided into five parts:Part one:In this paper,the current food safety issues were briefly reviewed,the pretreatment methods of complex matrix samples were summarized,and the significance of this topic and research content were clarified.Part two:A methanol salting out extraction system was established to discuss the four tetracycline detection problems in beef.The formation conditions and stability of the methanol salting out extraction system were studied experimentally.The true state of protein molecules in the extract was studied by Rayleigh scattering method,and the destruction of protein molecular structure by high concentration methanol extract was confirmed.There is a strong hydrophobic interaction between the protein molecule and tetracycline,and 70%?V/V?of the methanol extract can completely destroy this force and release the drug molecules.Due to the high polarity of methanol,the impurities such as fat-soluble protein in the extract are less.Add a small amount of PSA and C₁₈solid adsorbent,and centrifuge?5000 r/min?to achieve a good purification effect.The method is simple in operation,green and efficient,and the recovery rate is 76.8%⁹8.2%,and the detection limit is 0.039⁰.084?g/g.Part three:The residue extraction of quinolones?QNs?from beef was studied by 1%formic acid acidified methanol extraction system.The effects of different purifiers,extraction temperature and methanol concentration on the extraction system were investigated by high performance liquid chromatography.Due to the high polarity of methanol,the fat-soluble impurities do not easily enter the extract,and a small amount of PSA and C₁₈ can complete the extraction of quinolones in the sample,thereby simplifying the purification step.The extract is acidified with 1%formic acid,and the solution is highly protonated,making the quinolone drug easier to enter.The method can be applied to the detection of five quinolones?norfloxacin,ciprofloxacin,ofloxacin,gatifloxacin and lomefloxacin hydrochloride?in beef samples,and the recovery rates are between 79.1%and 103.8%.The detection limit is 36.8⁸6.5 ng/g.Part four:The ability of florfenicol and thiamphenicol to bind to bovine serum albumin was studied by molecular fluorescence spectroscopy.It was confirmed that the protein was closely related to florfenicol and thiamphenicol.Balanced dialysis techniques were used to examine their binding efficiency to actual beef samples.The use of 70%?V/V?methanol extract can promote the physical and chemical properties of protein molecules to change,destroy the molecular hydrogen bonding force,release the target molecule.The extract has less fat-soluble impurities,and a small amount of C₁₈ and NH₂ is added as a purifying agent to achieve a purifying effect.The recovery efficiency of this method is 79.8%¹01.9%,the relative standard deviation within the day is 0.9%².7%,and the daytime precision is 1.5%³.7%,which meets the testing requirements.Part five:Five kinds of nitrobenzenes in fish samples were extracted by acetonitrile aqueous solution in one step,and detected by high performance liquid chromatography.By optimizing the extraction conditions,the effects of extractant species,volume fraction of organic reagents and purification agent selection on the extraction rate of nitrobenzene compounds were discussed.Finally,80%?V/V?acetonitrile aqueous solution was selected as the extractant,and a small amount of C₁₈and PSA purification adsorbents were added to rapidly extract nitrobenzene from fish samples.The method has mild extraction conditions and is environmentally friendly.The results show that the method has good accuracy and precision,and the detection limit?LOD?is between 18.3 and 46.4ng/g,which can meet the daily testing requirements.