| Abstract [eng] |
This work investigates various aspects of developing the design of an electrochemical MIP sensor for melamine sensing. The relevance of this work is based on the lack of research and data to provide cheaper tools for sensitive, reliable, and fast food analysis. During the study, various electrochemical methods such as chronoamperometry, differential pulse voltammetry, and cyclic voltammetry were used to collect and interpret the data, and the Randles-Sevcik equations were applied to calculate the active surface area of the electrode. To improve the electrochemical properties of the sensor and to increase its stability for reliable analysis, various conditions for the sensor development were investigated and optimized: changing the polymerization solution environment, the effect of the parameters of the pulsed chronoamperometry synthesis method, the influence of the means of stabilization on the polymer's electrical conductivity, such as the electrochemical stabilization and the overoxidation, and the effect of the various ways to introduce the gold nanostructures into the system. It has been experimentally confirmed that the best synthesis and analysis medium for melamine detection in the present system is acidic, in BRB at pH 3. The data show that reducing the polymer layer positively affects the performance of the MIP. The best result was achieved when the synthesis was carried out at the following pulsed chronoamperometry method parameters: lower potential 10 s 0 V and upper potential 2 s +0.9 V. Applying a stabilization measure to the sensor after MIP synthesis by cyclic voltammetry in BRB solution resulted in an improved reproducibility of results. Oxidation of the polypyrrole during the operation of the sensor was found to have a significant negative effect on the reliability of the results. This influence was successfully reduced by overoxidation, with an average 12 times smaller current variation. The optimum overoxidation was carried out by chronoamperometry: potential +1.0 V, duration 30 s. Among the methods investigated for the incorporation of gold nanostructures into the system, such as the incorporation of prepared 13 nm Au NPs into the polymerization solution, Au NPs drop-casting and electrochemical coating of the nanostructures, chronoamperometric synthesis of the nanostructures and coating from a solution of 5 mM HAuCl4 and 0.1 M KNO3 was found to be the most suitable for the system, with the following parameters: potential: 120 s, -0.4 V. This allowed to increase the sensitivity of the sensor by a factor of 4 compared to the standard introduction of nanoparticles via a polymerization solution. The results obtained may help overcome the shortcomings and problems encountered in developing a melamine electrochemical sensor based on MIP technology. |
