Determination of Copper in the Presence of Various Amounts of Arsenic withL-Cysteine Modified Gold Electrodes

Simultaneous Measurement of Trace Levels of Hg, As, Sb, and Bi in Coastal Seawater with a Multichannel Chemical Vapor Generation Atomic Fluorescence Spectrometer

Trace levels of Hg, As, Sb, and Bi in coastal seawater have been simultaneously detected by a laboratory-built multichannel chemical vapor generation coupled to an atomic fluorescence spectrometer. The system was configured with a built-in electrochemical H2 generator as the fuel supplier to replace chemical H2 produced by the oxidation of potassium borohydride under acidic conditions in traditional instruments. The electrochemical H2 generator not only isolated the atomization process from the chemical vapor injection process but also improved the stability of atomization, excitation, and fluorescence emission in the hydrogen flame, making it easier to optimize conditions for CVG while introducing evaporating multielement vapors. Calibrations were obtained using a mixed standard solution of Hg(II), As(III), Sb(III), and Bi(III). The addition of KBr to a 3% (v/v) HCl solution was selected as the preservative to ensure the stability of 0.10 μg/L Hg(II) in a multielement standard solution for at least 15 days while also preserving μg/L levels of As(III), Sb(III), and Bi(III) stable. The method detection limits (LOD, 3σ) were 0.001, 0.015, 0.010, and 0.005 μg/L for Hg, As, Sb, and Bi, respectively. The relative standard deviations (RSD, n = 7) of the standard spiked seawater samples were 3.2% (0.020 μg/L Hg), 1.2% (0.50 μg/L As), 1.0% (0.50 μg/L Sb), and 3.5% (0.050 μg/L Bi), respectively. The recoveries of seawater samples spiked with different salinities were in the range of 84.5%(Sb)-114%(Hg). The system has been successfully applied to the simultaneous analysis of the four elements in the seawater samples collected from Xiamen Bay, Southeast China.

Preparation of GO/Fe3O4@PMDA/AuNPs nanocomposite for simultaneous determination of As3+ and Cu2+ by stripping voltammetry

One of the critical challenges in the simultaneous determination of As³⁺ and Cu²⁺ by stripping voltammetry is the overlapping of their oxidation peaks. Therefore, the engineering of nanostructured sensors in order to uplift their electrochemical performance is a significant issue for the codetection of As³⁺ and Cu²⁺. Herein, we modified a glassy carbon electrode with a new nanocomposite based on poly methyldopa along with gold nanoparticles immobilized on the surface of magnetic graphene oxide (GCE/GO/Fe₃O₄@PMDA/AuNPs) that can determine As³⁺ and Cu²⁺ with great sensitivity. Optimization of the measurement conditions by square wave stripping voltammetry (SWSV) caused the oxidation peaks of As³⁺ and Cu²⁺ to be distinguished significantly from each other, while the peak currents of As³⁺ and Cu²⁺ increased 9-12 fold, respectively, compared to the bare electrode. The proposed electrode exhibits low detection limits (S/N ≥ 3): 0.15 ppb for As³⁺ and 0.11 ppb for Cu²⁺. The GCE/GO/Fe₃O₄@PMDA/AuNPs also has good linearity over a wide concentration range from 5 to 500 ppb for As³⁺ and 0.5-750 ppb for Cu²⁺. The good recovery values were obtained for the analysis of As³⁺ and Cu²⁺ in pool and drinking water samples.

Electrochemical determination of arsenic in natural waters using carbon fiber ultra-microelectrodes modified with gold nanoparticles

We have developed an anodic stripping voltammetry method that employs carbon fiber ultra-microelectrodes modified with gold nanoparticles to determine arsenic in natural waters. Gold nanoparticles were potentiostatically deposited on carbon fiber ultra-microelectrodes at -0.90V (vs SCE) for a time of 15s, to form the carbon fiber ultra-microelectrodes modified with gold nanoparticles. Cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy coupled to an X-ray microanalysis system were used to check and confirm the presence of gold nanoparticles on the carbon fiber ultra-microelectrodes. Arsenic detection parameters such as deposition potential and deposition time were optimized allowing a detection range between 5 to 60µgL^-1. The developed modified electrodes allowed rapid As determination with improved analytical characteristics including better repeatability, higher selectivity, lower detection limit (0.9μgL^-1) and higher sensitivity (0.0176nAμgL^-1) as compared to the standard carbon electrodes. The analytical capability of the optimized method was demonstrated by determination of arsenic in certified reference materials (trace elements in water (NIST SRM 1643d)) and by comparison of results with those obtained by hydride generation atomic absorption spectrometry (HG-AAS) in the determination of the analyte in tap and well waters.