Voltammetric determination of traces of 4-chloroaniline in antiseptic samples on a cathodically-treated boron-doped diamond electrode

Abstract

Abstract Chlorhexidine (CRX) is the active substance in many antiseptic products and its main hydrolytic degradation product is 4-chloroaniline (4-CA), a compound with carcinogenic potential. This work presents a new electrochemical method for the determination of low concentrations of 4-CA in CRX-based antiseptic samples. Preliminary investigations using electrochemical impedance spectroscopy revealed a substantial decreased in the resistance to charge transfer after the cathodic treatment (82 Ω) in comparison with untreated (567 Ω) and anodically-treated BDD surface (308 Ω), which corroborated with the higher currents obtained for 4-CA by cyclic voltammetry on the cathodic treated surface. Considering the pH effect, higher currents verified in buffered solution with pH 6 suggests higher interaction between the hydrophobic BDD surface and the deprotonated 4-CA species (predominant species in this pH). Using a cathodically-treated BDD and a 0.04 mol L−1 Britton-Robinson buffer solution (pH 6), the optimized SWV method demonstrated high sensitivity, low limit of detection (25 nmol L−1), wide linear range (1–80 μmol L−1) and was applied for the analysis of two types of antiseptic samples (mouth rinse and hospital soap). The quantification of 4-CA was performed by the standard addition method with satisfactory recovery values (100–112%) after simple dilution of the samples in the supporting electrolyte. Hence the proposed method is capable to monitor 4-CA traces in commercial samples within the concentration level established by the US Pharmacopeia.