ABSTRACT
A novel promising carbon paste electrode with excellent potentiometric properties was prepared for the analysis of trihexyphenidyl hydrochloride (THP), the acetylcholine receptor and an anticholinergic drug in real samples. It contains 10.2% trihexyphenidy-tetraphenylborate ionic pair as the electroactive material, with the addition of 3.9% reduced graphene oxide and 0.3% of anionic additive into the paste, which consists of 45.0% dibutylphthalate as the solvent mediator and 40.6% graphite. Under the optimized experimental conditions, the electrode showed a Nernstian slope of 58.9 ± 0.2 mV/decade with a regression coefficient of 0.9992. It exhibited high selectivity and reproducibility as well as a fast and linear dynamic response range from 4.0 × 10-7 to 1.0 × 10-2 M. The electrode remained usable for up to 19 days. Analytical applications showed excellent recoveries ranging from 96.8 to 101.7%, LOD was 2.5 × 10-7 M. The electrode was successfully used for THP analysis of pharmaceutical and biological samples.
Subject(s)
Graphite , Pharmaceutical Preparations , Carbon , Electrodes , Potentiometry , Reproducibility of Results , TrihexyphenidylABSTRACT
The development of sensing coatings, as important sensor elements that integrate functionality, simplicity, chemical stability, and physical stability, has been shown to play a major role in electrochemical sensing system development trends. Simple and versatile assembling procedures and scalability make polyelectrolytes highly convenient for use in electrochemical sensing applications. Polyelectrolytes are mainly used in electrochemical sensor architectures for entrapping (incorporation, immobilization, etc.) various materials into sensing layers. These materials can often increase sensitivity, selectivity, and electronic communications with the electrode substrate, and they can mediate electron transfer between an analyte and transducer. Analytical performance can be significantly improved by the synergistic effect of materials (sensing material, transducer, and mediator) present in these composites. As most reported methods for the preparation of polyelectrolyte-based sensing layers are layer-by-layer and casting/coating methods, this review focuses on the use of the latter methods in the development of electrochemical sensors within the last decade. In contrast to many reviews related to electrochemical sensors that feature polyelectrolytes, this review is focused on architectures of sensing layers and the role of polyelectrolytes in the development of sensing systems. Additionally, the role of polyelectrolytes in the preparation and modification of various nanoparticles, nanoprobes, reporter probes, nanobeads, etc. that are used in electrochemical sensing systems is also reviewed.
ABSTRACT
The amperometric determination of cysteine, using an electrode based on ternary silver-copper sulfide, is presented. Electrochemical characterizations (using cyclic voltammetry) of three electrode materials revealed that the electrode based on the material that consists of jalpaite (Ag3CuS2), doped with a small amount of metallic silver, has the best electrocatalytical performance for cysteine oxidation. For the amperometric determination, 0.142 V at pH 5 and 0.04 V at pH 7 vs. Ag/AgCl, related to the electrocatalytical oxidation of thiol group, were chosen. Electrochemical impedance spectroscopy together with Fourier transform infrared spectroscopy (FTIR) revealed that oxidation takes place on the electrode surface with fouling effect, which does not affect a wide linear working range between 1 µM and 100 µM. Sensitivities, at pH 5 and pH 7, are calculated to be 0.11 µA µM-1 and 0.10 µA µM-1, respectively. The detection limits were determined to be 0.036 µM and 0.024 µM for pH 5 and pH 7, respectively. In the presence of uric acid, folic acid, ascorbic acid, and glucose no interference was noticed. This electrode showed remarkable stability and excellent reproducibility. The electrode was exploited for the determination of cysteine in a dietary supplement with the excellent recoveries.
