VOLTAMMETRIC DETERMINATION OF 1,4-NAPHTHOQUINONE DERIVATIVES

Abstract

In this work, we have studied the physicochemical behaviors of oxidation-reduction of 2,3-dichloro-1,4-naphthoquinone (NQ) and 2-chloro-3-((4-hydroxyphenyl) amino)-1,4-naphthoquinone (NQ1) synthesized on the basis of NQ, on impregnated graphite electrode. The nature of the electrochemical processes was determined and the mechanism of oxidation-reduction of substances was assumed. The operating conditions for the voltammetric determination of compounds on an impregnated graphite electrode were selected, such as the supporting electrolyte – 0.1 M NaClO4 solution in 96% ethanol (pH=2 for NQ, pH=10 for NQ1), V=100 mV·s-1, as well as the potential and time of accumulation (Eacc +1 V; tacc 50 s for NQ and Eacc -1 V; tacc 30 s for NQ1). It is shown that the pH of the supporting electrolyte has a high influence on NQ and NQ1 analytical signal. For NQ, the current reaches its maximum value at pH = 2. For NQ1, the opposite effect of pH on the current intensity is observed: the maximum current value is reached at pH = 12. The linear dependence of the reduction peak current at a potential of 0.12 V on the concentration of NQ is observed in the range 2·10-5 – 8·10-4 mol·l-1 with the regression equation I=3.14C - 0.35 (R2=0.9992). For NQ1, the linear range of the calibration curve of the electro oxidation current at a potential of -0.58 V on the concentration is maintained in the range 1·10-6 – 8·10-4 mol·l-1 with regression equation I=45.74C +0.37 (R2=0.9992). The detection limit (LOD) for NQ, calculated according to the 3S criterion, is 7.2·10-6 mol·l-1, for NQ1 8·10-7 mol·l-1. The accuracy of the method of analyzed compounds quantitative determination in the substance was checked by the "spiked test" method.