Voltammetric Sensor for Naproxen Enantiomers Based on a Paste Electrode Modified With a Chiral Nickel(II) Complex

An enantioselective voltammetric sensor (EVS) comprising a paste electrode made of graphitized thermal Carboblack C (CBPE) modified with a Ni(II) complex based on (S)-(2-aminomethyl)pyrrolidine and 3,5-di-tert-butylsalicylaldehyde was developed for the recognition and determination of naproxen (Nap) enantiomers. The proposed sensor was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS-SEM), Fourier-transform infrared spectroscopy (FT-IR), molecular dynamics and quantum chemical simulations, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) methods. Using the differential pulse voltammetry (DPV), the CBPE@(S)-Ni sensor was found to have good selectivity for Nap enantiomers (i_p1S/i_p1R = 1.43, i_p2S/i_p2R = 1.27 for the first/second peaks, respectively). The sensor demonstrates the highest sensitivity to (S)-Nap (6.44 and 6.90 μA/mM for the first and second peaks). The linear concentration range is from 5.0 × 10^-5 to 1 × 10^-3 M and from 2.0 × 10^-4 to 1 × 10^-3 M for (S)- and (R)-Nap, respectively, where the detection limits for the first and second peaks are 5.31 × 10^-7 M and 4.96 × 10^-7 M for (S)-Nap and 7.40 × 10^-7 and 6.79 × 10^-7 for (R)-Nap. The suggested sensor was successfully tested for the determination of Nap enantiomers in mixtures, in biological fluids, and in medicinal drug forms. In all the cases, the relative standard deviation (RSD) does not exceed 4.7%; the recovery percentage is in the range of 99.2%-101.3%.