Method for determining 2-methyl-5-isopropylcyclohex-2,5-diene-1,4-dione in dietary supplements and edible oils

Abstract

The subject of the application is a method for determining 2-methyl-5-isopropylcyclohex-2,5-diene-1,4-dione in samples of dietary supplements and edible oils, characterized in that an auxiliary electrode (3), a reference electrode (4) and a carbon paste electrode (5) as a working electrode, which is a Teflon electrode body filled with carbon paste, as well as a magnetic stirrer (6), are introduced successively into an electrochemical vessel (1) filled with a basic electrolyte solution (2), which is a hydrochloric acid solution with a concentration of 0.2 mol / L, wherein the electrode reaction of analyte oxidation takes place on the working paste electrode (5), and all three electrodes are connected to a potentiostat (7), each to a dedicated connector, and then the first voltammogram is recorded, constituting the so-calleda blank sample is taken, and in the next step, a second voltammogram is recorded by placing a solution of a food sample of the tested oil or supplement, prepared by mixing 100 µl of black cumin oil or black cumin oil taken from a supplement capsule with 800 µl of methanol, in an electrochemical vessel (1) with a basic electrolyte (2), and the suspensions thus prepared are shaken in a darkroom on a laboratory shaker, and then transferred to a thermostated laboratory centrifuge in order to separate the methanol layer from the sample oil, then the solutions are centrifuged at a temperature from 0°C to 25°C, after which the increase in current intensity is measured relative to the blank sample, then the third voltammogram is recorded by adding a portion of the standard solution to the electrochemical vessel (1) containing the basic electrolyte solution (2) and the sample solution 2-methyl-5-isopropylcyclohex-2,5-dien-1,4-dione at concentration 0.001 mol / L, resulting from dissolving the analyte in a volumetric flask, topped up with distilled water to the mark and mixed, then the increase in current intensity is measured relative to the blank sample, in the subsequent stages the fourth and subsequent voltammograms are recorded analogously after subsequent additions of the standard, and all voltammograms are recorded in the potential range from 0.0 V to 1.0 V with the required parameters of the SWV technique being: amplitude 25 mV, potential step 2 mV, frequency 50 Hz.