Study Of Cloud Point Extraction In Pesticide Residue Analysis And Instant Determination Of Formaldehyde

Residue of pesticides found in agriculture products, drinking water and environmental exposure has raised much concern from the general public in recent years. In order to protect persons' healthy, the maximum residue levels (MRL) in food were constituted by WHO/FAO-CAC. It is important to exploit simply, fast, efficient pre-treatment technologies for samples and high sensitive, high selective multi-pesticide detections technologies based on pesticide and veterinary drug residues in food and the requirement for international trade on food. The safty of the living environment and foods also cause people attention especially about formaldehyde pollution. The study of formaldehyde instant determination become valuable.The thesis includes three parts:In chapterâ… : The application of cloud point extraction in determination 6 types pesticides in milk by HPLCThe feasibility of employing cloud point extraction (CPE) as extraction and preconcentration method for recovery of herbicide from milk samples followed by HPLC analysis is demonstrated. An aqueous surfactant solution containing 6% Tween20 or Triton X-100 was used and then heated with appropriate concentration (NH₄)₂SO₄ or NaCl for extraction of herbicide. The extraction was analyzed by HPLC in next step. Six herbicides in milk were analyzed simultaneous. Results show linear dynamic range of detection of Tralkoxydim,Metribuzin and Bormoxynil were 20-10000 ng/ml, Mefenacet was 20-10000 ng/ml, Bensulfuron-Methyl and Nicosulfuron were 20-10000 ng/ml. The correlation coefficient were 0.9981～0.9997. The average recoveries of the six herbicides ranged from 85.09% to 96.74%. The relative standard deviations for the six herbicides were in the range of 1.90%～3.98%. The limit of detection about 6 type's pesticides is lower than GB MRL. The results indicate that the method developed is easier, faster, sensitive and less pollution. It can be used for analyses the other things.In chapterâ…¡: A new spectrophotometry method for instant determination of formaldehyde in dope In the presence of FeCl₃ and HCl, formaldehyde can form a purple complex with peptone The complex exhibited max absorption at 555nm. The absorption was linearly proportional to the complex concentration in the formaldehyde concentration range of 1～25μg/10mL, a correlation coefficient (r²) was 0.9997. The detection limit was 0.05μg/mL. This method was applied to the determination of formaldehyde in dope discoloring by the active carbon. And the recoveries were 96.46—103.32%, the relative standard deviations were 1.36—2.09% (n=6).In chapterâ…¢: A new method for instant determination of trace formaldehyde in alcoholA new method for determination of trace formaldehyde in beer was developed by a spectrophotometer at 555nm. Based on studies of reaction conditions, e. g. reagent concentration, reaction temperature and time, a colorimetric method was established. A 4ml volume of egg white reagent and a 1.0ml volume of FeCl₃ solution were added into a 4ml volume of a beer sample, and the mixture was heated at 70℃for 10 min. After cooling, the coloring solution was determined. The detection limits were 1～10μg/10ml in beer, a correlation coefficient (r²) was 0.996. The recoveries were 96.46—103.32% and relative standard deviations were 1.36—2.09% (n=6).