Study Of Rapid Determination Of Urea And Sulfur Dioxide In Foodstuffs

With the development of human social progress and economic globalization, foodsafety has become a global problem. The methods and instruments for the rapiddetermination of harmful components in foods are necessary.In this thesis，the rapid determination of urea and sulfur dioxide in foods wasresearched. The important determination methods of urea and sulfur dioxide weresummarized. The rapid determination methods of urea in milk and sulfur dioxide infoods are developed in this thesis. The work is of considerable significance and practicalvalue.In this thesis, two kinds of rapid and spot detection methods of urea in milk weredeveloped. One of detection methods was rapid colorimetey, which was based on thereaction between the analytes color reagent and Beer’s law. The urea in milk wasdetermined rapidly by the present method. The colorimeter was made up of ahigh-brightness LED，a light-to-frequency converter，a columniform absorption cell，a microcomputer，a LCD module and several keys. The colorimeter was small andportable. The characteristics of the equipment, the technical specifications, and theoperation were described in details. The calibration curve (correlation coefficient0.9998)is linear in the concentration range of0.001-0.050%and the determination limit is0.001%. Another detection method of urea in milk is test strip mehod. The urea can betransformed into carbon dioxide and ammonia with enzyme in the presence ofwater.When the pH value of the solution changes, the color of test strip changesbecause of the pre-added pH indicator. In this thesis, not only the experimentalconditions were optimized, but also real samples were analyzed. The good experimentalresults were obtained. The study provides effective detection method to control thequality of milk.The rapid determination of sulfur dioxide in food by pararosaniline hydrocloridespectrophotometry was also studied in this thesis. The ultrasonic technology wasapplied to treat the sample. The GDYQ-100M fast food safety analyzer was used todetermine sulfur dioxide. More then20real samples were analyzed at the optimal experimental conditions. The calibration curve (correlation coefficient:0.9998) is linearin the concentration range of0.050-1.000mg/L and the determination limit is0.050mg/L. Comparing the results obtained by the method with these obtained by nationalstandard method, there were no significant differences.