Electrochemical Sensors For Sulfite Detection And Applications In Food Sample

Sulfite is widely used in the foods processing as a kind of bleaching agents, preservatives and antioxidants. However, ingestion of excessive sulfite can produce detrimental effects on human health. The diversity of food samples and the instability of sulfite bring certain difficulty for detection of sulfite. Therefore, it is significant to effective monitoring of sulfite in foods. In order to solve these problems on detection of sulfite, we not only established the reliable detection methods, but also tested some potential stabilizers of sulfite which matched with the method of detection of sulfite in foods by developing a series of chemical modified electrodes.1、The performance of a series of potential stabilizer of sulfite were tested by cyclic voltammetry with glassy carbon electrode. The experiment of sulfite stabilization effects on propanol, fructose, ethanol, ethylene glycol, isopropanol and glycerol after24hours is obvious, but the acetonitrile and acetone did not show the performance of protection of sulfite. Electrochemical response signal recovery of the sulfite in the solution of3%(v/v) of isopropyl alcohol and5%(v/v) of propanol can reached96%and97%after72hours, these stabilizers showed good performance on sulfite. This result laid the foundation for the next step of the analysis of electrochemical detection of sulfite in real samples.2、In this work, a new sensors was developed for determination of sulfite. The method is based on the use of conductive carbon black (Super p-Li) instead of the ordinary graphite to prepare the carbon black electrode(CBE). The resulting electrodes can effectively improve the transfer rate of electron in the oxidation process of sulfite, and increase the effective contact area between the electrode interface and sulfite solution. The effective area of CBE is0.2542cm2, which has a remarkable enhancement compared with the common carbon paste electrode. According to the relationship between the sulfite oxidation peak potentials and pH, the oxidation of sulfite at CBE was the process of two electrons and two protons transfer. The external standard calibration curve was linear in the range of0.008～1.0mmol/L with a detection limit of6×10-6mol/L by using square wave voltammetry (SWV) combined with CBE. The proposed electrode exhibited several attractive features, including simple preparation, fast response, good stability and repeatability, and was successfully applied to the determination of sulfite in rice wine samples.3、A novel method for the selective extraction of free (pH8.4) and total sulfites (pH11.0) from muscle food and followed determination by a voltammetric sensor was reported. The proposed method was based on the eletrocatalytic oxidation of sulfite at modified glass carbon electrodes fabricated by immobilizing9μg of Acetylferrocene (AFc) on the surface of glass-carbon electrode along with35μg of carbon black (CB) to improve the electron transfer within polyvinyl butyral (PVB) membrane matrix. The external standard calibration curve was linear in the range of0.03～4.0mmol/L with a detection limit of15μmol/L. This method had been applied to the determination of free and total sulfite content in shrimp muscle spikelet samples and the results were compared with an ion chromatography method. The proposed electrode and analysis method were proved to be sensitive, accurate, rapid, and exhibited very good reproducibility and stability under the used conditions.4、In this work, the multi walled carbon nanotubes (MWNTs) was dispersed by dimethyl formamide (DMF), and then modified on a glassy carbon electrode to prepare MWNTs-Fe/GCE for determination of sulfite and eliminated the interference of hydroxymethyl sulfonic(SFS) in the same solution, and the proposal electrode was successfully applied to determination of SFS. By differential pulse voltammetry (DPV) combined with MWNTs-Fe/GCE detection of sulfite and SFS, the external standard calibration curve was linear in the sulfite concentration arrange of0.08～4mmol/L with a detection limit of5×10-5mol/L, and the SFS concentration arrange of0.06～5mmol/L with a detection limit of3×10-5mol/L. The proposed electrode were proved to eliminate the interference between sulfite and SFS. And the proposed method was successfully applied to the determination of sulfite and SFS in the same samples of dried beancurd sticks.