Study On Photoeletrochemical Analysis Of Flavin Compounds

The photoelectrochemical analysis is based on the energy transfer from light to electricity, by utilizing the correlation between the tested substances with photoelectrochemical reaction, to achieve the determination of the substance concentration. This analytical method-based on photoelectrochemical process is a new testing technology. Its outstanding characteristic is that the excitation and detection is completed step by step, and due to the separation of excitation source and signal detection, mutual non-interfering, so the blank value is very low. In relation to the photometric method, it has advantages of the simple equipment and low cost. Compared with the electrochemical method, it has advantages of better selectivity and higher sensitivity. Flavin compounds are the derivatives of 7,8-Dimethylisoalloxazine, mainly including riboflavin (RF), flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). From the molecular structure, flavin compounds have the conjugated double bonds, the rigid planar structure and the redox reaction site in the molecule, and they have good photochemical and electrochemical activity. On the other hand, they also have photosensitivity, an important photosensitive agent. Based on the photoelectric active of flavin compounds and photoelectrochemically analytical method, the photoelectrochemical methods were attempted for detecting flavin compounds in the paper.The main contents are as follows:1. The photoreduced mechanism of riboflavin (RF) was investigated based on the photochemical and electrochemical properties of RF. And a new photoelectron-chemically analytical method was developed for the determination of RF by combining the photoreduction of RF with subsequent electrode reaction. Under the optimized conditions of pH4.5, EDTA as photoreduced agent, bias voltage 0 V, illumination at 450 nm and light energy 15 mW/cm2, the photocurrent is proportional to the logarithm of RF concentration in the range of 5.00×10-10～5.00×10-5 mol/L with correlation coefficient of 0.998, and the detection limit was estimated to be 3.00×10-10 mol/L (S/N=3). The proposed method has been applied to the determination of RF in multivitamin tablet and millet, with the relative standard deviations of less than 7.86% and the recovery rates of 96%～105%. Compared with other methods for the determination of RF, the proposed method has various advantages, such as wide measurement range, high sensitivity, simple equipment and convenient operation.2. Based on the result of study for the photoelectrochemical analysis of RF, the quantitative methods applicable to FAD and FMN was further developed, respectively. The experimental conditions were optimized by selecting for the pH value of buffer solution, the electrolysis time, bias voltage, illumination time, EDTA concentration and light intensity. The results showed that the photocurrent is proportional to the logarithm of FAD and FMN concentration in the range of 5.00×10-10～1.00×10-5 and 1.00×10-10～1.00×10-5 mol/L, respectively.