Studies On The Electrochemical Determination Of Sudan Red In Foodstuffs And Honokiol, Magnolol In Traditional Chinese Medicines

In recent years, food safety and drug quality have obtained increasing attention. Therefore, it is very important to determine the harmful ingredients of food as well as the effective ingredients of medicines. The use of conventional electrode in electrochemical detection has many shortcomings in sensitivity, selectivity and response time. So the chemically modified electrode has alternatively appeared. In this paper, two kinds of chemically modified electrodes based on carbon nanotube and mesoporous SiO2 were individually prepared, and their application in food safety analysis and drug quality control was investigated in great detail. Major work is as follows:In the presence of dihexadecyl hydrogen phosphate (DHP), the insoluble muti-walled carbon nanotube (MWNT) was dispersed into water under ultrasonic condition, resulting in a stable and homogeneous MWNT/DHP suspension. After that, a MWNT/DHP composite film-modified electrode was achieved. The electrochemical behavior of Sudan I at the bare electrode, DHP film-modified electrode and MWNT/DHP film-modified electrode was compared. MWNT possesses many excellent properties such as large surface area, strong adsorption ability and numerous active sites. Therefore, MWNT/DHP composite film-modified electrode shows higher activity towards Sudan I and significantly increases its oxidation signal. Based on this, a highly sensitive, fast and convenient electrochemical method was established for the determination of Sudan I. The linear range is over the range from 4.03×10-8 to 4.03×10-6 mol/L, the detection limit for 3-min accumulation is 2.02×10-8 mol/L, the RSD for 10 parallel determinations is evaluated to be 8.4%. Finally, this method was applied to determine Sudan I in hot chili samples, and the average recovery is 97.8%.Mesoporous silica is a kind of very attractive electrode material due to its regular, uniform, adjustable channel structure, large surface area, strong adsorption ability and good stability. Herein, a kind of mesoporous SiO2 was synthesized using cetyltrimethyl ammonium bromide as a template. After that, a mesoporous SiO2-modified carbon paste electrode was fabricated. The electrochemical behavior of honokiol and magnolol was examined. Two highly sensitive, well-shaped and independent oxidation peaks appear at the mesoporous SiO2-modified carbon paste electrode. The peak potentials are 0.31 V and 0.44 V, respectively. The effects of pH value, amount of mesoporous SiO2 and accumulation time on the oxidation signals of honokiol and magnolol were studied, and the optimized parameters were achieved. Therefore, a new method for the simultaneous determination of honokiol and magnolol was developed. For honokiol, the linear range is from 2.0μg/L to 100.0μg/L, the detection limit for 3-min accumulation is 0.5μg/L and RSD for 10 parallel determinations is 5.8%. For magnolol, the linear range is over the range from 20.0μg/L to 200.0μg/L, the detection limit for 3-min accumulation is evaluated to be 10.0μg/L and RSD is 5.3% for 10 parallel determinations. Finally, this new method was applied to determine honokiol and magnolol in Cortex Magnoliae Officinalis and Huoxiangzhengqi oral solutions. The average recovery is 99.2%, suggesting that this new method has good accuracy.