Simultaneous Determination of Lead,Copper, and Mercury Free from Macromolecule Contaminants by Square Wave Stripping Voltammetry

Abstract

A novel approach for the voltammetric determination of Pb²⁺, Cu²⁺, and Hg²⁺ in the presence of macromolecule contaminants was developed. An Au nanoparticles array was directly electrodeposited onto the gold electrode surface followed by a further modification of a mercaptoethanesulfonate (MES) monolayer. Square wave stripping voltammetry (SWSV) of Pb²⁺, Cu²⁺, and Hg²⁺ was performed on the doubly modified electrode. The electrodeposited gold nanoparticles provided a significantly improved sensitivity. Simultaneously, the MES monolayer efficiently prevented the macromolecules accessing the electrode surface. Compared with the bare gold electrode, the doubly modified electrode has the ability to detect metal ions in the presence of macromolecule contaminants, even when their concentration reach 100 ppm. Under the optimal conditions, the detection limits of 0.16, 0.15, and 0.14 ppb for Pb²⁺, Cu²⁺, and Hg²⁺ were obtained, respectively. The calibration graphs were linear in the concentration range of 1–100 ppb. The results of the analysis of a real metallurgy wastewater sample were reported. The electrode system has a great potential for the direct determination of trace metals in the complex environment and biological samples.     

Anodic Stripping Voltammetric Determination of Lead（Ⅱ） Using Glassy Carbon Electrode Modified with Novel Calix[4] arene

A new glassy carbon electrode modified with novel calix[4]‐arene derivative was prepared and then applied to the selective recognition of lead ion in aqueous media by cyclic and square wave voltammetry. A new anodic stripping peak at ? 0.92 V (vs. Ag/Ag⁺) in square wave voltammogram can be obtained by scanning the potential from ? 1.5 to ? 0.6 V, of which the peak current is proportional to the concentration of Pb²⁺. The modified electrode in 0.1 mol/L HNO₃ solution showed a linear voltammetric response in the range of 2.0 × 10–⁸–1.0 × 10–⁶ mol/L and a detection limit of 6.1 × 10–⁹ mol/L. In the modified glassy carbon electrode no significant interference occurred from alkali, alkaline and transition metal ions except Hg²⁺, Ag⁺ and Cu²⁺ ions, which can be eliminated by the addition of KSCN. The proposed method was successfully applied to determine lead in aqueous samples.     

Simultaneous voltammetric analysis of lead,copper and mercury ions by carbon paste electrode based on 1-(3-aminopropyl) imidazole modified polymer

In this study, a carbon paste electrode modified with a novel 1-(3-aminopropyl) imidazole functionalised crosslinked chlorosulfonated poly(styrene)-divinyl benzene polymer was used for selective and sensitive determination of the trace amounts of Pb²⁺, Cu²⁺ and Hg²⁺ ions by square wave anodic stripping voltammetry. The effect of some parameters such as paste composition, pH, preconcentration time, reduction potential and time, type of supporting electrolyte and potential scan rate on the determination of metal ions were investigated to find the optimal conditions. The effective open-circuit accumulation of the studied metal ions was succeeded only by the modification of the carbon paste electrode with functional polymer. For 6 min open-circuit preconcentration, the detection limit of Pb²⁺, Cu²⁺ and Hg²⁺ was found to be 5, 9 and 14 µgL^?1, respectively at 100 mVs^?1. The results confirmed that the lower concentration levels of these trace metal ions can be determined with the increase of preconcentration time and/or potential scan rate. Good detection limits and large dynamic concentration ranges were also obtained for their binary and ternary mixtures. The optimised method was successively applied to determine the concentration of Pb²⁺, Cu²⁺ ions in the tap water sample and Cu²⁺ ion in the waste water sample in the presence of possible interfering species (RSD<1%, recoveries 96–110% for 4 min preconcentration).     

Zinc oxide nanostructured platform for electrochemical detection of heavy metals

ZnO nanoparticles (ZnO-NP) were prepared by a facile precipitation technique using di-isopropyl amine as precipitating agent. The morpho-structure and porosity of the as-prepared nano-powder were investigated by FT-IR analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET analysis. By drop-casting, a composite film was deposited to obtain ZnO-NP-Nafion/GCE modified electrode. The modified electrode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and square wave anodic stripping voltammetry (SWASV) for the detection of Pb²⁺, Cd²⁺, Cu²⁺, and Fe³⁺, and it was successfully applied for the detection of Pb²⁺ and Cu²⁺ in real water samples.     

A reactive electrode (reactrode) for the voltammetric determination of heavy metals in laboratories and for use as a passive monitor in remote analysis

The use of a reactive electrode (reactrode) consisting of graphite, a solid ion exchanger (HYPHAN) and paraffin for the batch analysis of Cd²⁺, Cu²⁺, Pb²⁺ and Hg²⁺ in aqueous samples and as a passive monitor for these metal ions is described. The metal ions are accumulated on the reactrode surface at an open-circuit potential in an ion-exchange reaction. After the accumulation, the ion exchanger-bonded metal ions are reduced to the metals which remain on the electrode surface. In a following step, the metals are anodically dissolved which is recorded by differential-pulse voltammetry. The 3s detection limits for the analysis of drinking water are: 1.1×10^-7 mol/l for Pb²⁺, 5×10^-8 mol/l for Hg²⁺ and 2.4×10^-7 mol/l for Cu²⁺.The reactrode developed can be used for the passive monitoring of heavy metals in aqueous streams if the reactrode is mounted in a wall-jet cell which is part of a flow-through system. Using this arrangement, it has been possible to determine Hg²⁺, Cu²⁺ and Pb²⁺ in drinking water after 20 hours of accumulation.     

Complexation of metal ions with the novel diazadithia crown ethers carrying two pyrene pendants in acetonitrile-tetrahydrofuran

Two crown ethers carrying pyrene side arms with nitrogen-sulfur donor atom were designed and synthesized by the reaction of the corresponding macrocyclic compounds and 1-bromomethyl-pyrene. The influence of metal cations such as Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ on the spectroscopic properties of the ligands was investigated in acetonitrile-tetrahydrofuran (1:1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Al³⁺, Zn²⁺, Fe²⁺, Ni²⁺, Cu²⁺, and Pb²⁺ with 16-membered crown ether. Similar results were obtained for Al³⁺, Fe²⁺, Hg²⁺, Cu²⁺ and Pb²⁺ with 14-membered crown ether. The results of spectrophotometric titration experiments disclosed the complexation stoichiometry and complex stability constants of the novel ligands with these cations. According to spectrofluorimetric titration measurements the 14-membered diazadithia crown ether showed sensitivity for Pb²⁺ with linear range and detection limit of 1.3 × 10^?6 to 5.2 × 10^?5 M and 5.2 × 10^?7 M, respectively. The 16-membered diazadithia crown ether showed sensitivity for Ni²⁺ with linear range and detection limit of 1.3 × 10^?7 to 5.2 × 10^?6 M and 4.1 × 10^?8 M, respectively.     

Complexation of metal ions with the novel diazadithia crown ether carrying two anthryl pendants in acetonitrile–tetrahydrofuran

A new crown ether carrying two anthryl groups with nitrogen–sulfur donor atom was designed and synthesized by the reaction of the corresponding macrocyclic compound and 9-chloromethyl anthracene. The influence of metal cations such as Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ on the spectroscopic properties of the ligand was investigated in acetonitrile–tetrahydofuran solution (1/1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Fe²⁺, Fe³⁺, Al³⁺, Cu²⁺ and Hg²⁺. The results of spectrophotometric titration experiments disclosed the complexation stoichiometry and complex stability constant of the novel ligand with Fe²⁺, Fe³⁺, Al³⁺, Cu²⁺and Hg²⁺cations. The presence of excess amounts of Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ cations caused an enhancement of anthryl fluorescence. The ligand showed good sensitivity for Zn²⁺ with respect to other metal cations with linear range and detection limit of 1.4 × 10^?7 to 4.1 × 10^?6 M and 1.0 × 10^?8 M respectively.     

Non-conductive nanomaterial enhanced electrochemical response in stripping voltammetry: The use of nanostructured magnesium silicate hollow spheres for heavy metal ions detection

Nanostructured magnesium silicate hollow spheres, one kind of non-conductive nanomaterials, were used in heavy metal ions (HMIs) detection with enhanced performance for the first time. The detailed study of the enhancing electrochemical response in stripping voltammetry for simultaneous detection of ultratrace Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ was described. Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. The anodic stripping voltammetric performance toward HMIs was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detection limits achieved (0.186 nM, 0.247 nM, 0.169 nM and 0.375 nM for Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺) are much lower than the guideline values in drinking water given by the World Health Organization (WHO). In addition, the interference and stability of the modified electrode were also investigated under the optimized conditions. An interesting phenomenon of mutual interference between different metal ions was observed. Most importantly, the sensitivity of Pb²⁺ increased in the presence of certain concentrations of other metal ions, such as Cd²⁺, Cu²⁺ and Hg²⁺ both individually and simultaneously. The proposed electrochemical sensing method is thus expected to open new opportunities to broaden the use of SWASV in analysis for detecting HMIs in the environment.     

The electrochemical stripping determination of tin in aqueous and nonaqueous media after its extraction

The anodic stripping voltammetric and chronopotentiometric determination of tin(IV) in aqueous and nonaqueous medium after its extraction using the rotating disc electrode made of glassy carbon with the mercury film was studied. The optimum composition of nonaqueous medium for the determination of tin is 0.2 M NaBr+5×10^?5M Hg²⁺ in 20 ml of the extract +30 ml of methanol. Tin(IV) was determined by anodic stripping voltammetry or chronopotentiometry down to the concentration 10^?7M. The selective determination of tin was studied. 10^?6M of tin(IV) was determined with an error ±4–5% even in the presence of metals: Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺ (5×10^?3M), Ag⁺ and Pb²⁺ (5×10^?4M), Cu²⁺ (1.5×10^?4M), Sb³⁺ and Bi³⁺ (5×10^?5M).     

Carbon Nanotubes/Ionophore Modified Electrode for Anodic Stripping Determination of Lead

Bifunctional combination of carbon nanotubes and ionophore is introduced for anodic stripping analysis of lead (Pb²⁺). Carbon nanotubes are employed to improve the detection sensitivity due to their excellent electrical conductivity and strong adsorption ability. An ionophore is utilized for its excellent selectivity toward Pb²⁺. The proposed carbon nanotubes/ionophore modified electrode shows improved sensitivity and selectivity for Pb²⁺. Low detection limit (1 nM), wide linear range (5 nM–8 µM) and excellent selectivity over other metal ions (Cd²⁺, Cu²⁺, and Hg²⁺) was obtained. The practical application has been carried out for determination of Pb²⁺ in real water samples.     

Eco‐friendly Sensors Developed by Herbal Based Silver Nanoparticles for Electrochemical Detection of Mercury (II) Ion

In our study, the single‐use & eco‐friendly electrochemical sensor platform based on herbal silver nanoparticles (AgNPs) was developed for detection of mercury (II) ion (Hg²⁺). For this purpose, the surface of pencil graphite electrode (PGE) was modified with AgNPs and folic acid (FA), respectively. The concentrations of AgNPs and FA were firstly optimized by differential pulse voltammetry (DPV) to obtain an effective surface modification of PGE. Each step at the surface modification process was characterized by using cyclic voltammetry (CV) and electrochemical impedence spectroscopy (EIS). The limit of detection (LOD) for Hg²⁺ was estimated and found to be 8.43 μM by CV technique. The sensor presented an excellent selectivity for Hg²⁺ against to other heavy metal ions such as Ca²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Mg²⁺, Ni²⁺, Pb²⁺, Zn²⁺, Co²⁺ and Mn²⁺. Moreover, a rapid, selective and sensitive detection of Hg²⁺ was successfully performed in the samples of tap water within 1 min.     

Simultaneous Determination of Cadmium,Lead, Copper and Mercury Ions Using Organofunctionalized SBA‐15 Nanostructured Silica Modified Graphite–Polyurethane Composite Electrode

A new sensor has been developed for the simultaneous detection of cadmium, lead, copper and mercury, using differential pulse and square wave anodic stripping voltammetry (DPASV and SWASV) at a graphite–polyurethane composite electrode with SBA‐15 silica organofunctionalized with 2‐benzothiazolethiol as bulk modifier. The heavy metal ions were preconcentrated on the surface of the modified electrode at ?1.1 V vs. SCE where they complex with 2‐benzothiazolethiol and are reduced to the metals, and are then reoxidized. Optimum SWASV conditions lead to nanomolar detection limits and simultaneous determination of Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ in natural waters was achieved.     

Silver(I)‐Selective PVC Membrane Potentiometric Sensor Based on a Recently Synthesized Calix[4]arene

A new PVC membrane potentiometric sensor for Ag(I) ion based on a recently synthesized calix[4]arene compound of 5,11,17,23‐tetra‐tert‐butyl‐25,27‐dihydroxy‐calix[4]arene‐thiacrown‐4 is developed. The electrode exhibits a Nernstian response for Ag(I) ions over a wide concentration range (1.0×10^?2?1.0×10^?6 M) with a slope of 53.8±1.6 mV per decade. It has a relatively fast response time (5–10 s) and can be used for at least 2 months without any considerable divergence in potentials. The proposed electrode shows high selectivity towards Ag⁺ ions over Pb²⁺, Cd²⁺, Co²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Sr²⁺, Mg²⁺, Ca²⁺, Li⁺, K⁺, Na⁺, NH₄⁺ ions and can be used in a pH range of 2–6. Only interference of Hg²⁺ is found. It is successfully used as an indicator electrode in potentiometric titration of a mixture of chloride, bromide and iodide ions.     

Simultaneous determination of trace levels of lead(II) and copper(II) by square wave stripping voltammetry using a glassy carbon electrode modified with hierarchical gold dendrites

A glassy carbon electrode was modified with gold hierarchical dendrites (Au HDs) by one-step electrodeposition in the presence of cytosine, which plays an important role in the formation of the Au HDs. This approach is simple, fast, feasible, controllable, without any seed, template, or surfactant. The modified electrodes were used for the simultaneous determination of Pb²⁺ and Cu²⁺ by square wave stripping voltammetry. The peak currents show good linear relationship with concentrations of Pb²⁺ and Cu²⁺ in the range of 5.0 to 15.0 μM. The recoveries of the spiked water samples are in the range of 94.0 %–107.4 % for Pb²⁺ and Cu²⁺, and their relative standard deviation are in the range of 2.7 %–4.3 % for Pb²⁺ and Cu²⁺, respectively (n?=?3).

A new sensitive and selective sensor for heavy metal ions based on tannin extracted from the skin of Punica granatum L

This article presents the development of a sensor made from a gold electrode and a receiving polymeric membrane based on tannin extracted from the skin of Punica granatum. L (pomegranate) for real-time detection of heavy metals in a hydrous environment. The basic principle of this device is the complexing (chelating) of metal ions through the adjacent hydroxyl groups contained in the chemical structures of the tannins. The electrochemical characterisation was performed by using electrochemical impedance spectroscopy and square wave voltammetry. Other morphological and structural analyses were performed by using Fourier transform infrared spectroscopy and atomic-force microscopy. The results obtained showed the high sensitivity of the developed device (detection limits of 6.35 × 10^?9 g L^?1 for Cu²⁺, 1.1 × 10^?8 g L^?1 for Cd²⁺ and 2 × 10^?7 g L^?1 for Pb²⁺) and the possibility of simultaneously detecting several heavy metals, each one in a highly selective manner with highly acceptable response time (48s).     

Conductometric studies and application of new Schiff base ligand as carbon paste electrode modifier for mercury and cadmium determination

A new chemically modified carbon paste electrode by 2,2?-((pyridine-2,6-diylbis(azanylylidene))bis(methanylylidene))diphenol (L) ligand has been made and used as a sensor for determination of trace mercury and cadmium ions with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. Complexation studies of the ligand with Cu²⁺, Zn²⁺, Hg²⁺, Ni²⁺ and Cd²⁺ ions by conductometric method in acetonitrile–ethanol mixture at 25°C show that the ML complexes have formed. The formation constants of complexes were calculated from the computer fitting of the molar conductance–mole ratio data, and the stability of the resulting complexes varied in order of Cd²⁺ > Hg²⁺ > Cu²⁺ > Zn²⁺ > Ni²⁺. Then a simple and effective chemically modified carbon paste electrode with L was prepared, and the electrochemical properties and applications of the modified electrode were investigated. Under the optimal conditions, the detection limit was 0.0494 μg L^?1 and 0.0782 μg L^?1 for cadmium and mercury ions, respectively, and the linear range for both metal ions were from 1 to 100 μg L^?1. The electrode shows high sensitivity, reproducibility and low cost, and was successfully applied to determination of Cd²⁺ and Hg²⁺ ions in water samples with recovery in the range of 97–101%.     

Electrochemical Behaviour of the Anticancer Dacarbazine‐Cu2+ Complex and Its Analytical Applications

Electrochemical reduction of the dacarbazine‐Cu²⁺ complex was investigated using cyclic voltammetry and square wave voltammetry at a hanging mercury drop electrode. The reduction of the dacarbazine‐Cu²⁺ complex is irreversible. A reduction mechanism is proposed comprising a one‐electron reduction of the Cu²⁺ directly within the complex. The sharp peak of the adsorbed dacarbazine‐Cu²⁺ complex associated with an effective interfacial accumulation facilitates the determination of the anticancer drug dacarbazine in pharmaceutical formulations and biological fluids. Detection limits for dacarbazine of 6.12×10^?10 M, 1.57×10^?10 M and 1.97×10^?9 M were achieved for the determination of the drug in vial, human urine and serum, respectively.     

多臂碳纳米管/Nafion复合材料修饰玻碳电极测定痕量的铅离子

A composite material of nitric acid oxidized multiwalled carbon nanotube （MWNT） and Nation was prepared. Such composite was modified on a glassy carbon electrode to determine trace of lead by differential pulsed voltammetry. In pH=6.47 NaNO3 solution, Pb^2＋ ions were accumulated on the modified electrode at -0.4 V. Compared with a bare and a Nation film coated electrode, the composite coated GC electrode can reduce the accumulating potential and eliminate the toxic character of mercury. The calibration plots were linear at low concentration of 5.0× 10^-9-2.0× 10^-8 mol/L and high concentration of 2.5× 10^-8-5.0× 10^-6 mol/L. The performances characteristics indicate that the electrode can be used to determine trace Pb^2＋ ions.     

Remote Stripping Analysis of Lead and Copper by a Mercury‐Coated Platinum Microelectrode

The performance of a remote stripping sensor based on mercury microelectrodes (MM‐RS) for the in situ detection of trace metals in aquatic systems, was investigated. The submersible device employed here consists of a single mercury‐coated platinum disk microelectrode assembled in a two‐electrode cell configuration, and connected remotely by a 30 m long shielded cable. First, the MM‐RS device is characterized in Ru(NH₃) and Pb²⁺ synthetic aqueous solutions by applying cyclic voltammetry and anodic stripping voltammetry (ASV), respectively. The results obtained show that the small electrode dimensions and the related low currents involved, the long remote connection cable or the use of a two‐electrode system do not cause noise effects or uncompensated resistance problems in the measurements. Using square‐wave voltammetry in the stripping step, linear calibration graphs for Pb²⁺ ions over the concentration range 1×10^?9?5×10^?7 M were obtained, and a detection limit, DL, of 0.15 nM was found. The relative standard deviation (RSD), at 5×10^?8 M Pb²⁺ level, was within 5%. The effect of humic acid and of sodium dodecylsulfate surfactants on the stripping responses was also investigated. The performance of the submersible MM‐RS system was tested for the in situ monitoring of the labile fraction of lead and copper on a site of the Lagoon of Venice. In situ Pb²⁺ and Cu²⁺ concentrations were monitored for about 8 hours, by leaving the sensor immersed in the lagoon waters (2 m depth) and recording the response every hour. Under these field conditions, reliable in situ data for the labile fraction of these metal ions with a satisfactory precision, the RSD being within 7 and 9 % for lead and copper, respectively, were obtained.     

Simultaneous Determination of Thallium and Lead on a Chemically Modified Electrode with Langmuir– Blodgett Film of a p‐tert‐Butylcalix[4]arene Derivative

A new voltammetric sensor, Langmuir–Blodgett (LB) film of a p‐tert‐butylcalix[4]arene derivative modified glassy carbon electrode, was designed and successfully used in simultaneous determination of Tl⁺ and Pb²⁺ by square‐wave anodic stripping voltammetry. Under the optimum experimental conditions, this newly developed sensor reveal good linear response for Tl⁺ and Pb²⁺ in the concentration range of 3×10^?8–4×10^?6 mol L^?1 and 2×10^?7–2×10^?5 mol L^?1 respectively. The detect limits are 2×10^?8 mol L^?1 for Tl⁺ and 8×10^?8 mol L^?1 for Pb²⁺. Using proposed method, Tl⁺ and Pb²⁺ in environment samples were determined with satisfactory results.