| Food safety concerns everyone’s health and has attracted more attention around the world. Veterinary drug residues in food of animal origin are one of the main impacts on food safety. Hence, the development of analysis methods for the determination of veterinary drugs residues in food is necessary to ensure food sasfety. There are two prominent problems in veterinary drug residues analysis, one is the pretreatment means, and the other is the separation and deterniantion method. Since the food matrices are complex and veterinary drug residues are of trace level, more effective sample pretreatment and sensitive determination method should mathch the requirement of the veterinary drug residues analsis in food. Hence, the study on the sample preparation technology and chromatographic analysis is crucial to determination of veterinary drug residues in food.The main study content of this thesis was to develope the sample preparation technology and chromatographic analysis method to determine veterinary drugs residues in food. The main purpose of this thesis was to resolve the questions of sample preparation technology and chromatographic analysis, in order to esbilish methods for determination of residues of glucocorticoids, benzimidazoles and organic arsenic in food. The study provides technical and thesis support for controlling veterinary drug residues in food and evaluating on animal food safety.1. Development of a method for simultaneous determination of residues of glucocorticoid in animal derived food.A confirmatory and quantitative method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine the presence of eight glucocorticoids (prednisone, prednisolone, hydrocortisone, methylprednisolone, dexamethasone, betamethasone, beclomethasone, and fludrocortisone) in edible tissues of swine, cattle, sheep and chicken, egg and milk is described. After deconjugation in alkali media, samples were extracted with ethyl acetate for glucocorticoids followed by solid-phase extraction clean-up and reconstitution in the LC mobile phase. The hydrolysis procedure with sodium hydroxide was used to reduce handling time. A single-step solid-phase extraction method was optimized which is suitable for the clean-up of the compounds of interest in many diverse tissue matrices. LC separations were performed on a C18column with gradient elution using acetonitrile and water (containing0.2%formic acid) and the two epimers betamethasone and dexamethasone were successfully separated. LC-electrospray ionization (ESI)-MS/MS in negative mode with selected reaction monitoring (SRM) mode was performed to improve method sensitivity and reduce matrix interference. Two SRM transitions were used for each compound. The optimized procedure was successfully applied to monitor the food at the2008Summer Olympics Games in Beijing, China, demonstrating the method to be simple, fast, robust, and suitable for identification and quantification of glucocorticoids residues in foods of animal origin.2. Development of a method for simultaneous determination of residues of benzimidazole and its metabolites in animal derived food.A confirmatory and quantitative method using HPLC-UV and HPLC-MS/MS have been established for simultaneous determination benzimidazole and its metabolites in the muscles and livers of swine, cattle, sheep, and chicken, muscle of fish, eggs, and milk. Sample prepatation techniques including solid phase extraction, and accelerated solvent extraction (ASE) were applied in extracting benzimidazole and its metabolites in animal derived foods. The sample pretreatment has been simplified for using the ultrasonic extraction and solid phase extraction in the method. The volume of the organic solvent was decreased using the acceleratet solvent extraction method, avoiding the toxicity solvent using, and realizing sanple-handling automatism in the method. HPLC-UV analysis was performed on C18column eluted and applied to simultaneous determination benzimidazoles. HPLC-MS/MS analysis was performed on C18column eluted by a mobile phase of acetonitrile spiked with a buffer solution consisting of5mmol l-1formic ammonium, and the analytes were detected by LC-ESI-MS/MS in positive mode with selected reaction monitoring (SRM) mode. The method has been successfully applied to monitoring real samples containing benzimidazole and its metabolites, which demonstrated that it is a simple, fast and robust method, and could be used as a regulatory tool to determine the residues of benzimidazole and its metabolites in animal-origin foods.3. Development of a method for simultaneous quantification of residues of organic arsenic in animal derived food.HPLC-UV and HPLC-MS/MS have been established for simultaneous determination of4organic arsenic (arsanilic Acid, roxarsone, nitarsone, carbarsone) in the muscles and livers of swine and chicken, the muscle of fish and egg. And some conditions such as sample extraction, purification and sample solvent have been deeply investigated in this experiment. Samples were extracted with methanol-acetonitrile-trichloroacetic acid solution in an ultrasonic bath, and purified by solid phase extraction on strong anion exchanger cartridges. The sample pretreatment has been simplified for using the ultrasonic extraction and solid phase extraction in the method. The volume of the organic solvent was decreased using the sample pretreatment method. This simply and little contaminative method with the familiar materials can be applied on monitoring the use of multi-organic arsenic in animal food. The samples were analyzed on an Hypersil ODS C18liquid chromatography column using a gradient program with methanol and1%acetic acid by HPLC-UV. The samples were analyzed on a HILIC Silica liquid chromatography column using a gradient program with acetonitrile and ammonium acetate by HPLC-MS/MS with electrospary ionization method. HPLC-UV and HPLC-MS/MS have been firstly established for simultaneous determination of organic arsenic in animal dereived foods. The methods have good sensitivity, specificity, and which can be appilied to monitor the possible misuse of organic arsen residues in animal derived foods. The experiment can be taken as an instruction to do studies on analysis methods for determination of multi-residues in animal tissues and provide technical support for evaluation on animal food safety. |
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