Composites of chitosan polyelectrolyte complexes with cyclodextrins were used for selective recognition of atenolol enantiomers in pharmaceuticals and human urine.

A practical application composite based on mixed chelate complexes [M(S-Ala)₂(H₂O)_n]–[M(S-Phe)₂(H₂O)_n] (M = Cu(II), Zn(II); n = 0–1) as chiral selectors in enantioselective voltammetric sensors was suggested. The structures of the resulting complexes were studied by XRD, ESI-MS, and IR- and NMR-spectroscopy methods. It was determined that enantioselectivity depends on the metal nature and on the structure of the mixed complex. The mixed complexes, which were suggested to be chiral selectors, were stable under the experimental conditions and provided greater enantioselectivity in the determination of chiral analytes, such as naproxen and propranolol, in comparison with the amino acids they comprise. The best results shown by the mixed copper complex [Cu(S-Ala)₂]–[Cu(S-Phe)₂] were: i_pS/i_pR = 1.27 and ΔE_p = 30 mV for Nap; and i_pS/i_pR = 1.37 and ΔE_p = 20 mV for Prp. The electrochemical and analytical characteristics of the sensors and conditions of voltammogram recordings were studied by differential pulse voltammetry. Linear relationships between the anodic current and the concentrations of Nap and Prp enantiomers were achieved in the range of 2.5 × 10⁻⁵ to 1.0 × 10⁻³ mol L⁻¹ for GCE/PEC-[Cu(S-Ala)₂]–[Cu(S-Phe)₂] and 5.0 × 10⁻⁵ to 1.0 × 10⁻³ for GCE/PEC–[Zn(S-Ala)₂(H₂O)]–[Zn(S-Phe)₂(H₂O)], with detection limits (3 s/m) of 0.30–1.24 μM. The suggested sensor was used to analyze Nap and Prp enantiomers in urine and plasma samples.

A voltammetric sensor was developed based on a glassy carbon electrode with aluminophosphate zeolite finely dispersed on its surface, modified with a polyelectrolyte complex of chitosan with succinyl chitosan and betulinic acid, for the selective detection and determination of naproxen enantiomers. The electrochemical and analytical characteristics of the sensor were studied, and the effective electrode surface area (A = 9.8 ± 0.5 mm²) and charge transfer resistance (R_et = 649.9 ± 0.4 Ω) were calculated. In determining naproxen enantiomers, calibration characteristics are linear in the range from 2.5 × 10^–5 to 1 × 10^–3 M with limits of detection of 1.1 × 10^–7 and 1.5 × 10^–7 M and limits of quantification of 3.6 × 10^–7 and 4.9 × 10^–7 M for R- and S-naproxen, respectively. The sensor is more sensitive to R-naproxen (∆E_p = 60 mV, i_pR/i_pS = 1.40). The proposed sensor was used to recognize and determine naproxen enantiomers in human urine and plasma samples. Statistical evaluation of the results by the standard addition method showed that there was no systematic error.