Hematite Nanoparticle-Modified Carbon Paper as a Promising Electrochemical Sensor for Atropine Detection in Beverages

This study describes the electroanalytical determination of atropine in beverages using a carbon paper (CP) electrode modified with Fe2O3 nanostructures. The incorporation of nanoparticles of a transition metal oxide on CP led to an improvement in the electrochemical response of the electrode using the technique: square wave voltammetry (SWV). Morphological characterization of CPE/Fe2O3 developed by Field Emission Scanning Electron Microscopy (FESEM), shows a relatively uniform distribution of Fe2O3 nanoparticles on the CP surface. The optimization of variables of pH and the amount of modifying agent were relevant to maximize the efficiency of the modified electrode. The evaluation of the pH effect shows that the maximum current response occurs at pH 11.5 in Britton-Robinson buffer, and the optimum amount of Fe2O3 was 1 mg/mL, giving the best response, standing out for an optimum active surface for the detection of atropine. Electrostatic calculations show that at pH 11 the surfaces become negatively charged, having better affinity with protonated atropine, compared the deprotonated state. This pH is beyond atropine pKa, hence, the peak in current at pH 11.5 indicates that the surface induces a shift in pKa, allowing the prevalence of protonated atropine at this high pH. The limit of detection and quantification (LD and LQ) recorded using the CP/Fe2O3 electrode were 0.075 and 0.250 mM, respectively. In the case of real samples, using the standard addition method, the presence of interferents did not significantly affect the detection of atropine, obtaining satisfactory recovery percentages.