Study On The Determination Of Vitamin C In Plants By Indirect Kinetic Spectrophotometric Method

Vitamin C(L-ascorbic,Victim C)also known as L-ascorbic acid,Chemical name:2,3,5,6-four hydroxy-2-hexenoic acid-4-lactone,containing 6 carbon atoms of acidic polyhydroxy compounds,can also be regarded as acidic hexose derivatives,and hexose enolic acid lactone structure.Vitamin C has a very important physiological function for the antioxidant system,plant photosynthesis and growth regulating protection,vitamin C is also one of the active substances in human and animals' life.Vitamin C in plants provides for human a rich and convenient source of vitamin C,the determination of vitamin C content in plants is an important indicator of the quality of plant products.There are many methods for the determination of vitamin C in plants,such as:the Redox Titration method,the Electro chemical method,the Absorption Spectrophotometry method,the Fluorescence Analysis method,the Chromatography method,etc.But many kinds of plant products,different plants and the same plant in different organs of vitamin C content is different,the chemical compositions of different plant products are various and the differences are great,each kind of determination of vitamin C and analysis methods have their own limitations and appropriate conditions.Therefore,this study intends to establish a new method for the determination of vitamin C,and try to increase the choice of a method for the determination of vitamin C.The main research contents and results are as follows:1.To establish an indirect iodometric kinetic spectrophotometric method for the determination of vitamin C.The color system of the method comprises starch,vitamin C,potassium iodate,sulfuric acid.The kinetic study results show that this system is composed of potassium iodate and trace vitamin C redox reaction quantitative formation of I2,I2 and starch reaction quantitatively to produce blue inclusion compound,I2 of the disintegration of the blue inclusion compound,three chemical reactions to form a reaction system of velocity difference.The dynamic reaction process of the color developing system is affected by the temperature,to obtain the maximum absorbency A.The concentration of vitamin C in the range of 1.38×10-4?4.82×10-4 mol·L-1 shows good linear relationship with Amax,r>0.999,follows Ron Bo-Bill's law.2.In this study,the concentration of each substance in the color system is optimized.The starch concentration is 8?13 mg·mL-1,vitamin C concentration is 1.38×10-4?4.82x10-4 mol·L-1,the concentration of sulfuric acid is 0.075 mol·L-1,potassium iodate concentration is 0.187 mol· L-1.Study the temperature to significantly affect the color system.The results show that,the kinetic process of color system by temperature effects of larger,in the process of analysis and test,the ordinary temperature control measures,meet the analysis results on the error requirements.Method using vitamin C tablets and vitamin C injection test results:RSD<1.1%;the recovery rate was in between 95.0%?96.3%;LOD was 8.17×10-7 mol·L-1;LOQ was 2.55x10-6mol·L-1;interference experiments showed that the vast majority of the common ions and the reduction of less than vitamin C substances do not interfere with the determination;compared with the results of the determination of the iodine quantity method,this method can obtain the ideal results,but the result of this method is more close to the mark,the method has the advantages of less reagent consumption,low analysis cost,high analysis efficiency,no toxicity and no pollution,etc.3.In the color system preferably each material concentration conditions,on the content of vitamin C inkiwifruit andthe orange commercially tested,and with two 2,6-chlorine indophenol titration results are compared,the recoveries of this method were 98.8%,96.45%,and RSD was 0.80%,1.03%.The precision and accuracy of the method are high,and the sample is more simple and convenient.The method is suitable for the determination of vitamin C content in most plant products.