Determination Of Natural Products In Apples And Pesticide Residues In Vegetables

In recent years, natural products have attracted much attention for its unique flavor, pharmacological and clinical effects. At the same time, food safety issues have also become the focus of attention, so it is pressing to set up methods to detect diet-related residues. Set up a fast and effective detection method is the goal of analysis. Therefore, we studied detection methods for natural products and pesticide residues.In the second chapter, a method was set up to determine gallic acid, protocatechuic acid, chlorogenic acid, caffeic acid and rutin in fresh smashed apples by HPLC/DAD simultaneously, and then the method was used to do varieties discrimination. In order to keep the original composition of polyphenols, we didn’t use traditional machining operation such as, crushed, pressed, freeze-dried and so on. To control browning, three different ways were tested and ascorbic acid with ultrasonic was applied. Two different extraction procedures have been tested and methanol-water-acetic acid (30:69:1, v/v/v) was chosen to be the best extraction solvent. After optimizing experimental conditions and instrument parameters, the method was used to detect polyphenols in seven apple varieties:Gala, Fuji, Delicious,8th Apple U.S., Golden Apple, Green Apple and Red Rose. The chromatographic separation was performed on an Atlantis C18(250mm×4.6mm, particle size5μm) with gradient elution program using a mixture of2%aqueous acetic acid (v/v) and acetonitrile as mobile phases within20min at270nm wavelength. The variations of the contents of five polyphenols were:gallic acid (ND～1.81μg/g), protocatechuic acid (ND～1.79μg/g), chlorogenic acid (13.81～189.4μg/g), caffeic acid (6.82～45.02μg/g) and rutin (0.96～18.55μg/g). By analyzing the polyphenol contents, apple varieties could be successfully discriminated by distribution diagram, being the contents of chlorogenic acid (abscissa) and rutin (ordinate) contribute most to the discrimination.In the third chapter, we set up a UPLC-MS/MS detection method for11kinds of pesticides:aldicarb sulfoxide, aldicarb sulfone, methomyl,3-hydroxy-carbofuran, aldicarb, carbofuran, carbaryl, imidacloprid, carbendazim, phoxim and avermectin. At the same time, the method was used to study the matrix effects of detected pesticides in three samples. Acetonitrile was chosen as extraction solvent considering the polarity and solubility of the pesticides. In order to decrease the pigment contamination to the column and mass spectrum, the last step to dissolve pesticides was2.5mL methanol+2.5mL water and then the mixture was filtrated by membrane. Methanol and1mmol/L ammonium acetate (gradient elution program) were chosen as mobile phases for mass analysis. The method was used to study matrix effects of the11pesticides in cabbage, cowpea and spinach. The effects of pure solvent spiked standard curve and matrix spiked standard curve on recoveries were compared. It was found that the same pesticide presents different matrix effects in the three matrixes. And in the same substrate, the matrix effects of tested pesticides are different from one another. The results could be used to guide pesticide detection experiment.