Electrochemical screening of selected β-blockers at a polarized liquid-liquid interface

This paper describes the electrochemical behavior of five β-blockers at the polarized liquid-liquid interface formed between aqueous solution (sodium chloride solution or Britton-Robinson buffers) and bis(triphenylphosphoranylidene)ammonium tetrakis(4-chlorophenyl)borate (BTPPATPBCl) dissolved in 1,2-dichloroethane (the organic phase). All measurements reported in this work were conducted using cyclic voltammetry (CV). The effects of the concentration of analytes, the pH of the aqueous phase, and applied electrochemical parameters on the analytical performance of the studied system are studied and discussed. The linear dynamic ranges (LDRs) of the studied β-blockers were in the range of 5-200 μmol L^-1 and the lowest limit of detection (LOD) value was determined for pindolol (LOD = 1.96 μM μmol L^-1). The highest LOD value was 4.96 μmol L^-1 found for nebivolol. In addition, physicochemical parameters such as the formal Galvani potential difference (Δaqorgϕ), formal Gibbs free energies of the ion transfer reaction (ΔaqorgG') and partition coefficients (log P'_aq/org) for all studied molecules were determined. The latter were compared and correlated with the available literature values of log P_octanol. Finally, a standard addition method was used to determine the concentration of nebivolol in pharmaceutical preparations using a platform based on the electrified liquid-liquid interface.