Determination Of Thiamine And Riboflavin By Polarographic Wave

VitaminB₁ ,also called thiamine or antineuritic vitamin, is one of B clan vitamins and consists of a pyrimidine ring and a thiazole ring. It is colourless crystalline solid, readily dissolves in water, and is very steady in the acid solution while unstable. In the alkaline solution thiamine undergoes oxidation and be destroied. Thiamine exist crust with plumule in seed mainly. In the body, thiamine participates in catabolism of candy in the form of coenzyme, has a function to protect the nervous system; It also can promote the stomach to wriggle, increases the appetite. Lacks of thiamine, multiple neuritis will cause. It has become one of the concerned fields in life sciences. Riboflavin (Vitamin B₂) is another important vitamin of the B complex functioning as an intermediary in the transfer of electrons in biological redox reactions. The deficiency of riboflavin is associated with eye lesions, skin disorders and cellular growth. It is widely present in cereal, vegetable, fruit, milk and meat. Numerous riboflavin preparations are becoming widely used to compensate for the possible deficiency. Therefore, the development of its analytical method has many practical meanings.In recent years, electrochemical methods have been widely used in bioanalytical chemistry. This thesis studies the determination of thiamine and riboflavin by polarography. The thesis is divided into four chapters.Chapter one summarizes some major quantitative analysis methods of thiamine and riboflavin. Futhermore, this chapter also summarizes the theory and researches of polarographic adsorptive wave on the dropping mercury electrode.In chapter two, the determination method of riboflavin is studied by polarographic adsorptive wave.A sensitive polarographic oxidation wave of riboflavin with Ep = -0.04V(vs.SCE) has been observed by using single sweep polarography in 0.12mol/L H2SO4 buffer solution. The peak height is linearly proportional to the concentration of riboflaviin in the range of 0.025～9.0μg/mL. The method has been used to determine the riboflavin in the pharmaceutical tablets with satisfactory results. The mechanism study has showed that the polarographic wave is attributed to the oxidation of riboflavin strongly adsorbed on DME surface.In chapter three, the determination method of riboflavin is studied by the reduction wave of the photolysis products of riboflavin. Based on its polarographic wave, a new method for the determination of riboflavin was proposed. In pH 9.3 NH3-NH4Cl buffer solution, the reduction wave of the photolysis products of riboflavin with peak potential -0.63 V (vs. SCE) was produced. The peak height of the wave was linearly proportional to the concentration of riboflavin in the range of 0.01～17.5μg/mL. The detection limit is 0.005μg/mL. The method has been used to determine the riboflavin in the pharmaceutical tablets, the results was satisfactory.In chapter four, the determination method of thiamine is studied by a reduction wave of S^2- . In 0.5 mol/L NaOH buffer, S^2- products a polarographic reduction wave. The peak height of the wave was linearly proportional to the concentration of thiamine in the range of 0.05¹4.0μg/mL. The method has been used to determine the thiamine in the pharmaceutical tablets with satisfactory results.