A square-wave voltammetric method for analysing the colour marker quinizarine in petrol and diesel fuels

This work presents an electroanalytical method based on square-wave voltammetry (SWV) for the determination of quinizarine (QNZ) in a mixture of Britton–Robinson buffer 0.08 mol L−1 with 30% of acetonitrile. The QNZ was oxidized at glassy carbon electrode in and the well-defined peak at +0.45 V vs. Ag/AgCl can be used for its determination as colour marker in fuel samples. All parameters were optimized and analytical curves can be constructed for QNZ concentrations ranging from 2.0 × 10−6 mol L−1 to 1.4 × 10−5 mol L−1, using f = 60 Hz and Esw = 25 mV. The method offers a limit detection of 4.12 × 10−7 mol L−1 and a standard deviation of 4.5% when six measurements of 1.25 × 10−5 mol L−1 are compared. The method was successfully applied for determining QNZ in gasoline and diesel oil and the obtained results showed good agreement with those reported previously.