Voltammetric determination of thujone in herbal matrices in the presence of Triton X-100

Abstract

A simple, sensitive and rapid method of low concentration of thujone determination using Controlled Growth Mercury Drop Electrode and Differential Pulse Voltammetry was described. The reduction of thujone in phosphoric acid or potassium nitrate, involves a quasi-reversible and adsorption-controlled two-electron process. In voltammetric experiments the addition of ethanol and Triton X–100 is recommended.Experimental conditions, such as composition of supporting electrolyte, concentration of Triton X-100 and operation parameters were established. The optimal electrolyte should contain: 0.04 mol L−1 phosphoric acid (pH = 1.9) or 0.05 mol L−1 potassium nitrate (pH = 6.4), 0.0002% Triton X-100 and 9.6% ethanol. The calibration graph was linear from 0.7 to 140 mgL−1 of thujone in H3PO4 as supporting electrolyte and from 0.7 to 115 mgL−1 of the analyte in KNO3. The detection limit was 0.4 mgL−1 in H3PO4 and 0.6 mgL−1 in KNO3, with the correlation coefficient of 0.998. The influence of interfering substances, such as Al(III), Bi(III), Cd(II), Cr(III), Cu(II), Pb(II), Tl(I), V(III) and Zn(II) was studied. The proposed method was validated by the thujone recovery study from the specially prepared spiked herbal matrices and alcohol extract. The considered real sample was thuja oil, in which thujone was successfully determined. All measurements were performed without sample preparation.