A method for the highly sensitive determination of acetylcholine (ACh) and choline (Ch) that employs a graphite-like carbon film electrode containing 6.5% platinum (Pt) nanoparticles was developed for use as a detector in microbore liquid chromatography (LC) with a postcolumn enzyme reactor. The film electrode was prepared by RF cosputtering carbon and Pt, which requires only a one-step formation process. This method can control the Pt content of the film at a relatively low deposition temperature (below 200 degrees C). The average size of the Pt nanoparticles was 2.5 nm. The film electrode showed excellent electrocatalytic activity, high sensitivity, and negligible baseline drift when detecting hydrogen peroxide. The electrode was modified with glucose oxidase and responded rapidly to glucose with a much more stable baseline current than at a Pt bulk electrode based sensor. Therefore, it is appropriate to employ the electrode to detect trace amounts of biomolecules, such as neurotransmitters and hormones combined with various oxidase enzymes. We used the electrode as a detector for microbore LC and observed a low detection limit of 2.5 and 2.3 fmol (10-microL injection) for ACh and Ch, respectively, which is approximately 1 order of magnitude lower than that of a Pt bulk electrode.
Palladium nanoparticle‐loaded carbon nanofibers (Pd/CNFs) were synthesized by the combination of electrospinning and thermal treatment processes. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that spherical Pd nanoparticles (NPs) are well‐dispersed on the surfaces of CNFs or embedded in CNFs. X‐ray diffraction (XRD) pattern indicates that cubic phase of Pd was formed during the reduction and carbonization processes, and the presence of Pd NPs promoted the graphitization of CNFs. This nanocomposite material exhibited high electric conductivity and accelerated the electron transfer, as verified by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The Pd/CNF‐modified carbon paste electrode (Pd/CNF‐CPE) demonstrated direct and mediatorless responses to H2O2 and NADH at low potentials. The analytical performances of the Pd/CNF‐CPEs towards reduction of H2O2 and oxidation of NADH were evaluated. The high sensitivity, wider linear range, good reproducibility, and the minimal surface fouling make this Pd/CNF‐CPE a promising candidate for amperometric H2O2 or NADH sensor.
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