Voltammetric determination of ethylvanillin and methylvanillin sum at carbon paste electrode modified by sodium dodecyl sulfate in selected foodstuffs

A new voltammetric method without using high cost and health risk nanomaterials has been developed for quantitative determination of ethylvanillin and methylvanillin sum, compounds that are used as food additives. The method is based on direct electrochemical oxidation of these biologically active compounds using square wave voltammetry at carbon paste electrode with surface modified by sodium dodecyl sulfate (SDS/CPE) performed in 0.1 M phosphate pH 6.0 buffer. Working conditions such as pH value of supporting electrolyte, type of surfactant, accumulation time of surfactant, and parameters of square wave voltammetry were optimized. In comparison with bare carbon paste electrode, excellent reproducibility characterized by a relative standard deviation of approximately 0.3% was obtained at the SDS/CPE. Linear range from 1.0 × 10−6 to 2.0 × 10−5 M, limits of quantification 9.8 × 10−8 M and detection 2.9 × 10−8 M were found at pulse amplitude 70 mV and frequency 50 Hz selected as optimum for ethylvanillin quantification. For methylvanillin, a linear range from 7.0 × 10−8 to 2.0 × 10−5 M and limits of quantification 7.0 × 10−8 M and detection 2.0 × 10−8 M were also determined. The procedure was validated using standard high-performance liquid chromatography method in the analysis of selected complex foodstuffs such as commercial baking sugar, biscuits, and an alcoholic drink. The results showed that a direct voltammetric approach is economically advantageous and reliable for the determination of ethyl- and methylvanillin, which is fully comparable to the reverse phase HPLC used as the ISO standard.