No abstract

This paper describes an electroanalytical method for the determination of metribuzin using a thin film mercury electrode by chronopotentiometry.

A novel, simple, sensitive and reliable electrochemical method for the riboflavin determination using chronopotentiometry with glassy carbon electrode was developed. The most important instrumental parameters of chronopotentiometry including type and concentration of supporting electrolyte, initial potential and current range were examined and optimised in respect to riboflavin analytical signal. Riboflavin provided well defined reduction signal at -0.12 V vs. Ag/AgCl (3.5 mol/L KCl) electrode in 0.025 mol/L HCl. Under optimal conditions, linear response of riboflavin was observed in the concentration range of 0.2-70 mg/L with achieved limit of detection of 0.076 mg/L and limit of quantitation of 0.23 mg/L of riboflavin. Common vitamins and excipients did not interfere with the determination. The proposed method was successfully applied for determination of riboflavin in commercially available pharmaceutical preparations. The obtained results were in statistical agreement to the contents declared by manufacturer and to those obtained by HPLC used as a comparative method.

This study compares different methods for the removal of oxygen from the solution prior to the chronopotentiometric determination of the insecticide imidacloprid on glassy carbon electrode. The research included the application of the chemical method involving addition of sulfite ion, and the physical method of purging the sample with nitrogen stream, as well as their combination. By comparing analytical signals of imidacloprid, chemical method showed almost the same efficiency as conventional physical method, while the best reproducibility was achieved by applying chemical method with addition of the saturated sodium sulfite solution. The method is very simple and can be applied for deoxygenation of the solution prior to the chronopotentiometric analysis. The application of the chemical deoxygenation significantly shortened duration of the chronopotentiometric analysis of imidacloprid from approximately 15 min to 1 min. [Projekat Ministarstva nauke Republike Srbije, br. III 46009]