Study And Application Of Solid-phase Extraction-hplc On The Analysis Of Vitamin And Antibiotics In Food

In recent years, more and more attention is paid to the food quality and safety, the food additives and the maximum residue levels (MRL) in food becomes more and more important due to endanger the human health. Therefore, the drug residue analytical methods of high selectivity and high sensitivity will be urgent need to be developed for providing the credibility valid data in the aspects of controling a food safety. With development and application of the various analytical instrument, the sample pretreatment technique has become a key step in food analysis. So, the goal of this study is to develop a new on-line technique of the molecularly imprinted solid-phase extraction-HPLC for the preconcentration, clean-up and determination of antibiotic residues in food.This thesis consists of four chapters and as follows:Chapter one: In this paper, the application and development of the molecular imprinting solid-phase extraction (MISPE) technique in food safety analysis was reviewed.Chapter two: The solid-phase extraction (SPE) was performed using Chromabond-SB cartridges to enrich the folic acid in health products. Tetra-n-butylammonium was used as an ion-pairing reagent. C18 column was used as the separation column, with 0.05 mol/L KH2PO4 solution: 0.01 mol/L Tetra-n-butylammonium:acetonitrile (88 : 2 : 10 V/V, pH = 5.5) as the mobile phase. The results of HPLC analysis show that the linear range of folic acid was 0.06 - 2.40μg/ml, the related coefficient was 0.9996, the detection limits was 0.008μg/mL, the yield was 95.14 % - 102.87 %.Chapter three: Molecularly imprinted polymers were prepared with tetracycline as the template molecule. The imprinted condition of the polymers were optimized by selectivity experiment. The molecularly imprinted polymer was used as SPE sorbents, and SPE protocol were optimized (include: condition, load, washing and elution). The present MISPE coupled with high performance liquid chromatography was applied for the determination of tetracycline, oxytetracycline, chlortetracycline and doxycycline in milk samples. The limit of detection of the method was 0.027 ~ 0.052 mg/kg, the recoveries was 76.0 %～95.8 %, and the relative standard deviations was 2.7 % ~ 6.8 %.Chapter four: The molecularly imprinted polymer monolithic column was in situ polymerized in a traditional stainless-steel chromatographic column by using ofloxacin as the imprinted template molecule. The imprinted condition of the polymers were optimized. Scatchard analysis show that two classes of binding sites existed in the imprinted polymers, with their maximum apparent binding capacity estimated to be 17.81μmol/g and 53.89μmol/g, respectively. The present monolithic column coupled with on-line column-switching liquid chromatography was successfully applied for the quantitative determination of ofloxacin, enrofloxacin and ciprofloxacin in honey samples with satisfactory results.