Multivariate approach in voltammetric identification and simultaneous determination of eugenol, carvacrol, and thymol on boron-doped diamond electrode

The paper presents multivariate partial least-squares calibration model defined for the identification and simultaneous determination of phenolic terpenoids—eugenol, carvacrol, and thymol—by means of the differential pulse voltammetry. For the first time, using boron-doped diamond electrode signal, electrochemical distinction of carvacrol and thymol, despite the short distance between the peaks (15 mV), was described. The analytes' concentrations applied in the calibration model were selected using the 3-factorial central composite design. The multivariate partial least-squares model, with optimized data pre-processing, was used for determination of eugenol, carvacrol, and thymol in the concentration ranges of 0.77–13.86, 0.58–10.40, and 0.73–7.32 mg/dm³, respectively. The quality of the method, expressed by the root-mean-squared error of calibration was 0.55, 0.20, and 0.26 mg/dm³ for the specified analytes. The recovery in the analysis of the pure signals was 98.92%, 101.62%, and 101.46%, what confirmed the possibility of clearly distinguishing the thymol and carvacrol peaks. In the spiked honey samples, the accuracy of eugenol, carvacrol, and thymol determination, expressed by the root-mean-squared error of prediction, was in the range 0.20–0.83 mg/dm³, and recovery in the range 80.9–111.9%. Application of the presented model not only enables electrochemical identification and simultaneous determination of eugenol, carvacrol, and thymol, but also allows rapid, accurate, and low-cost verification of authenticity of the commercial products. Graphical abstract:

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