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This paper presents a simple, sensitive, selective, cost-effective indirect voltammetric method for determining hydrazine using a poly(Eriochrome black T) modified pencil graphite electrode (p-EBT-PGE). Alizarin Red S (ARS) was used as a mediator in acetic acid–acetate buffer (pH 5.5) and 0.2 M KCl. The difference between the mediator's oxidation currents measured in hydrazine's presence and absence served as the analytical response for voltammetrically determining hydrazine. The ARS–hydrazine system's voltammetric properties at the p-EBT-PGE were also investigated. The limit of detection and two analytical ranges of the method were estimated to be 0.87 nM and 2.9 to 10.0 nM and 3.0 to 60.0 μM. The method has the best limit of detection among reported voltammetric methods. The recoveries in tap water, wastewater, and drinking water samples were between 99.60% and 104.74%, while the relative standard deviations were between 1.6 and 4.2. Uncertainty calculations were also evaluated for hydrazine-spiked samples by following a top–down approach. [ABSTRACT FROM AUTHOR]

Chloramphenicol (CAP) is a widely used, broad spectrum antibiotic that contains a nitrobenzene moiety with a possible poisonous feature. Thus, the development of low cost, simple, and rapid analytical methods for the reliable CAP quantification is necessary. Starting from the nitro group electroactivity, the cyclic voltammetric properties of CAP were investigated at the common commercially available, disposable pencil graphite electrode (PGE). The effect of the electrode material, the electrolyte pH and the potential scan rate were investigated. At 2H type PGE, the CAP cyclic voltammograms presented an anodic and two cathodic diffusion controlled, pH-dependent peaks, each involving the exchange of two electrons and two protons. Based on CAP main reduction peak at PGE in pH 5.00 Britton Robinson buffer, a square wave voltammetric (SWV) method was developed for its quantification from 2.50 × 10−6 to 7.50 × 10−4 mol L−1 with a limit of detection (LoD) of 1.39 × 10−6 mol L−1. Moreover, the anodic peak was also employed for the first time for a CAP linear sweep voltammetric (LSV) assay (2.50 × 10−6 to 1.00 × 10−3 mol L−1; LoD 6.09 × 10−7 mol L−1 CAP). Both voltammetric methods using the cost-effective PGE were applied for the determination of CAP in pharmaceuticals, obtaining recoveries of 100.9 ± 1.4% (relative standard deviation of 3.54%) for SWV and 100.7 ± 1.4% (relative standard deviation of 3.55%) for LSV. [ABSTRACT FROM AUTHOR]

Herein the synergistic properties of electrochemically reduced graphene oxide–antimony nanoparticles (ERGO-SbNPs) were leveraged for the ultrasensitive determination of bisphenol A (BPA) in water samples using disposable pencil graphite rods. A novel pencil-graphite multi-electrode array was utilized as the coating tool resulting in the production of highly reproducible and disposable single-use ERGO-SbNP-coated pencil graphite rods. This coating method effectively mitigated the fouling caused by BPA by-products during oxidation. The analytical determination of BPA oxidation on the single-use ERGO-SbNP-coated pencil graphite rods demonstrated an impressive 0.0,125 µM detection limit, surpassing the USEPA drinking water standard of 0.087 µM. Furthermore, the developed electrochemical sensor exhibited exceptional reproducibility for BPA in tap water samples from Western Cape, South Africa with few interferences. The study's findings not only highlight the sensor's superior performance but also present a promising alternative to existing anti-fouling measures. [ABSTRACT FROM AUTHOR]

In order to conquer the shortcomings of commercial SPME coatings: they can't stand high temperature, are easy to drop off, the longevity of usage is short and they are too expensive, we used pencil lead as a new sorbent to analyze the alcohol in water. The linear range is 5x10[SUP-6]-5x10[SUP-8]g/mL. The detection limit is 5x10[SUP-9]g/mL. We also used this method to determine the concentration of alcohol in environment water. The recoveries are 107.5% and 97%. The RSD is 5.9%. Hence the pencil lead is a very good material for solid-phase microextraction (SPME). [ABSTRACT FROM AUTHOR]

A gold (Au) nanoparticle-modified graphite pencil electrode was prepared by an electrodeposition procedure for the sensitive and rapid flow injection amperometric determination of hydrazine (N2H4). The electrodeposited Au nanoparticles on the pretreated graphite pencil electrode surface were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and electrochemical impedance spectroscopy. Cyclic voltammograms showed that the Au nanoparticle-modified pretreated graphite pencil electrode exhibits excellent electrocatalytic activity toward oxidation of hydrazine because the highly irreversibly and broadly observed oxidation peak at +600 mV at the pretreated graphite pencil electrode shifted to −167 mV at the Au nanoparticle pretreated graphite pencil electrode; in addition, a significant enhancement in the oxidation peak current was obtained. Thus, the flow-injection (FI) amperometric hydrazine sensor was constructed based on its electrocatalytic oxidation at the Au nanoparticle-modified pretreated graphite pencil electrode. The Au nanoparticle-modified pretreated graphite pencil electrode exhibits a linear calibration curve between the flow injection amperometric current and hydrazine concentration within the concentration range from 0.01 to 100 µM with a detection limit of 0.002 µM. The flow injection amperometric sensor has been successfully used for the determination of N2H4 in water samples with good accuracy and precision. [ABSTRACT FROM AUTHOR]