Application of Screen Printed Diamond Electrode, Coupled with Point-of-Care Platform, for Nanomolar Quantification of Phytonutrient Pterostilbene in Dietary Supplements: An Experimental Study Supported by Theory

Herein, a screen-printed diamond electrode (SPDE) coupled with a point-of-care platform (30 mu L-drop concepts, single-drop-detection approach) was successfully applied for the electrochemical determination of pterostilbene (PTS). Cyclic voltammetry identified irreversible oxidation of PTS, where oxidation peak was shown to be strongly dependent on the pH of the working environmental. Although the proposition of the detailed electrochemical oxidation mechanism of PTS goes out of the scope of the present research, we have determined the most probable reactive site of our analyte, by utilizing DFT-based reactivity descriptors (Fukui functions). For electrochemical quantification of PTS, oxidation peak at 0.32 V (vs. Ag/AgCl) was followed in presence of 0.5 mol L-1 of Briton-Robinson buffer solution (pH = 9). Coupled with the optimized parameters of differential pulse voltammetry (DPV), SPDE detected PTS in two linear ranges (first range was from 0.011 to 0.912 mu mol L-1; second range was from 0.912 to 4.420 mu mol L-1), providing the LOD and LOQ on a nanomolar level (3.1 nmol L-1 and 10.0 nmol L-1, respectively). The selectivity of the optimized DPV method was found to be excellent, with the current changes of less than 7%, in the presence of ten times higher concentrations of the certain interferences. The practical applicability of the SPDE and single-drop-detection approach in dietary supplements (with a declared PTS content of 50 mg/tablet), with the recovery values ranging from 95 to 102%, shows that the developed method has high potential for precise and accurate PTS detection, as well as exceptional miniaturization possibilities of relevant equipment for on-site sensing.

Automated summary

A screen-printed diamond electrode coupled with a point-of-care platform was used for the electrochemical determination of pterostilbene. The oxidation of pterostilbene was found to be pH-dependent, and the most probable reactive site of the analyte was determined using DFT-based reactivity descriptors. The optimized differential pulse voltammetry method showed excellent selectivity and nanomolar-level detection limits for pterostilbene.