Determination Of Heavy Metal Ions Research Articles

Voltammetry determination of Cd(II) and Pb(II) at TiO2/reduced graphene oxide modified electrodes

AbstractIn this article, a TiO2/reduced graphene oxide (rGO) composite was synthesized from rGO and soluble titanium hydroxide‐peroxide complexes. The obtained materials were characterized by X‐ray diffraction, scanning electron microscopy, nitrogen adsorption/desorption, Raman spectroscopy and energy dispersive X‐ray spectroscopy‐elementary mapping. The TiO2/rGO composite was used as an electrode modifier for developing an electrochemical sensor to simultaneous analysis of Cd(II) and Pb(II) by using differential pulse anodic stripping voltammetry (DP‐ASV). Under optimal conditions, the linear correlation between the stripping peak current and the metal ion concentration is good in the range of 5–100 ppb for both metals (R2 ≥ 0.998), and a low detection limit (3.17 ppb for Cd(II) and 2.42 ppb for Pb(II)) was obtained. The interference study revealed that some metal cations had little influence on the DP‐ASV signals of Cd(II) and Pb(II). In addition, the developed electrode exhibited satisfied reproducibility and repeatability. The TiO2/rGO‐modified electrode was tested toward the detection of Cd(II) and Pb(II) in river waters and the obtained exceptional recoveries and results were further associated with AAS results. This study indicates that the TiO2/rGO composite might be an alternative for practical applications in the electrochemical determination of heavy metal ions in aquatic solutions.

Development of Amperometric Enzyme Biosensor for Determination of Heavy Metal Ions in aqueous samples

An amperometric urease inhibition-based biosensor was developed to detect Pb2+ and Cr3+ ions in water matrix. The modified GCE/ZnO/urease electrode was developed by immobilizing ZnO nanoparticles and urease using gelatin and glutaraldehyde as crosslinking agent. With urea as a substrate, ZnO catalytic activity was examined through cyclic voltammetry. Working conditions of the biosensing system were optimized in terms of current generated in the presence of substrate (urea) as a function of different variables. Optimal sensor activity (current response) was obtained with a urease loading of 4 µl and ZnONPs concentration of 1.5 mg/L. For solution parameters, optimum pH was in the range of 7.0-7.5, optimum temperature was 35oC, optimal substrate concentration 40 µl. Evaluation of some key biosensing properties revealed relatively stable biosensor activity within the first 7 days, good reproducibility with an RSD of 3.61%. Limits of detection (LOD) for the biosensor ranged from 0.04 - 0.07 while limits of quantitation (LOQ) ranged from 0.22- 0.13 ppm. Applying the developed biosensor to real samples was evaluated by analysing water samples from Kasuwangada River in Mubi North Local Government Area. The system showed good percentage recovery of the added heavy metal standard (0.05 – 0.25 ppm). Percentage recovery within the acceptable range of 98.00% to 103.00% was observed for Pb2+, 92.00% - 102.00 % recovery for Cr3+. Analysis of real samples and assessment of obtained results against a standard method (AAS) showed minimal differences. The developed biosensor showed sufficient sensitivity to the analysed sample and gave quantitative information on the Pb2+ and Cr3+content of the sample. Keywords: Biosensor, Heavy Metals, Urease enzymes, Inhibition studies, Enzyme activity

Rapid, simple, and simultaneous electrochemical determination of cadmium, copper, and lead in Baijiu using a novel covalent organic framework based nanocomposite.

It is of great significance to develop a simple and rapid electrochemical sensor for simultaneous determination of heavy metal ions (HMIs) in Baijiu by using new nanomaterials. Here, graphene (GR) was utilized to combine with covalent organic frameworks (COFs) that was synthesized via the aldehyde-amine condensation between 2, 5-dimethoxyterephthalaldehyde (DMTP) and 1, 3, 5-tris(4-aminophenyl) benzene (TAPB) to prepare a new GR/COFDPTB/GCE sensor for electrochemical sensing multiple HMIs. Compared with the glass carbon electrode (GCE), GR/GCE and COFDPTB/GCE, the developed sensor exhibited excellent electrochemical analysis ability for the simultaneous detection of Cd2+, Pb2+, and Cu2+ owing to the synergistically increased the specific surface area, the periodic porous network and plenty of effective binding sites, as well as the enhanced conductivity. Under the optimized experimental parameters, the proposed sensor showed good linearity range of 0.1-25μM for Cd2+, and both 0.1-11μM for Pb2+ and Cu2+ with the detection limits of Cd2+, Pb2+, and Cu2+ being 0.011μM, 8.747nM, and 6.373nM, respectively. Besides, the designed sensor was successfully applied to the simultaneous detection of the three HMIs in Baijiu samples, suggesting its good practical application performance and a new method for the rapid detection of HMIs being expended.

The application of barcode readable assay and linear regression RGB analysis using a customized smartphone app in on-chip electromembrane extraction for simultaneous determination of heavy metal ions

This paper presents an on-chip electromembrane extraction (OC-EME) followed by RGB analysis with a barcode-readable customized app for the determination of three heavy metal ions; Cr(VI), Ni(ΙΙ), and Cu(ΙΙ) in water samples. First, the OC-EME procedure was performed on a single transparent platform including three divided channels for extraction of analytes and subsequently complex formation with chromogenic reagents. The RGB values of colorful complexes were then analyzed by Photoshop software and green value intensities of all three colors showed the best concentration dependence signal. Effective parameters such as the composition of supported liquid membrane (SLM), the voltage of extraction, the composition of donor and acceptor solutions, sample volume, and flow rate were investigated and optimized. Also, a smartphone app was developed for RGB analysis on a barcode-readable program to detect and quantify the extracted heavy metal(s). A fast, easy, and accurate quantification analysis was offered using principal component analysis (PCA) and a trained linear regression model. Under optimized conditions, good calibration fittings were observed within the ranges of 0.05–1.5 mg l−1 for Cr(VI), 1.0–70.0 mg l−1 for Ni(II), and 0.5–30.0 mg l−1 for Cu(II) via the customized app. Intra- and inter-day RSDs% of the method were obtained less than 6.9 % and 7.8 %, respectively. Finally, the proposed procedure was successfully applied for the analysis of target ions in water samples with relative recoveries between 85.0 % and 116.4 %.

A covalent organic frameworks@gold nanoparticles@graphene nanocomposite based electrochemical sensor for simultaneous determination of trace Cd2+, Pb2+ and Cu2+

It's very exciting to develop an electrochemical sensor for simple, rapid and simultaneous determination of heavy metal ions in Baijiu by applying new nanocomposites. Herein, a novel COFDPTB@gold nanoparticles (AuNPs)@graphene (GR) was obtained via combining COFDPTB synthesized using the Schiff-base condensation between 2, 5-dimethoxyterephthalaldehyde and 1, 3, 5-tris(4-aminophenyl) benzene with AuNPs and GR. Owing to the high porosity and abundant adsorption sites of COFDPTB, the outstanding electrical conductivity of AuNPs and GR, as well as the high specific area and synergy of COFDPTB, AuNPs and GR, the proposed sensor exhibited excellent analysis performance for the detection of Cd2+, Pb2+ and Cu2+. Under optimized conditions, the sensor showed good linearity range of 0.5–18 μM for Cd2+, and both 0.5–6.0 μM for Pb2+ and Cu2+ with the detection limits of 3.025 nM, 5.849 nM and 9.993 nM, respectively. In addition, the recovery measurement suggested the practicality of the prepared sensor.

Integrating catalytic role of gold nanoparticles with in-situ confinement effect of zirconium-based metal-organic frameworks for electrochemical determination of methylmercury

Catalytic redox reactions and size matching effect between the target molecule and sensing material are reliable methods for highly efficient determination of heavy metal ions. In this work, the electrochemical determination of methylmercury (CH3Hg+) was carried out gold nanoparticles (AuNPs) incorporated into four zirconium-based metal organic frameworks (MOF) with different pore diameters, namely MOF-801, (University of Oslo) UiO-66, UiO-67, UiO-68. The work relates the role of dicarboxylic ligands of different lengths to the AuNPs load capacity and the adsorption and reduction of CH3Hg+. The voltammetric properties of CH3Hg+ at different modified electrodes were studied by differential pulse anodic stripping voltammetry (DPASV). It was found that the CH3Hg+ electrochemical behavior was greatly influenced by the pore confinement effect of MOFs. Under the optimal conditions, the pore sizes of Au/UiO-67 are matched to CH3Hg+ molecule and they showed the highest response current. The possible reduction process of CH3Hg+ at the sensitive interface was explored by X-ray photoelectron spectroscopy (XPS) and chronoamperometry (CA). These four Au/MOFs modified GCE can also be used in detection of CH3Hg+ spiked in river water, confirming their potential application in the rapid detection of methylmercury in environmental samples.

BiW9-based electrochemical sensor for the simultaneous determination of cadmium(II) and lead(II) in water

Heavy metal pollution has been considered as an important concern for the environment, and effective detection methods are crucial for the sensitive and selective determination of toxic heavy metal ions such as lead and cadmium. Among various detection methods, electrochemical stripping analysis has been regarded as an efficient approach for the determination of heavy metal ions, especially on bismuth-based materials. Polyoxometalates have been received lots of attention and widely applied in many fields. However, the bismuth-containing polyoxometalate has never been reported for the determination of heavy metals. In this study, Na9[BiW9O33]·16H2O (BiW9) was utilized to construct an electrochemical sensor towards the simultaneous detection of Cd(II) and Pb(II). The prepared bismuth-containing polyoxometalate BiW9 was characterized by X-ray diffraction and Fourier transform infrared spectroscopy, which was then casted onto the surface of glassy carbon electrode (GCE) to test the electrochemical behavior by square wave anodic stripping voltammetry. The results showed that BiW9/GCE possesses a good electroanalytical performance for the simultaneous determination of Cd(II) and Pb(II) with wide linear ranges and low detection limits. Moreover, the sensor shows good selectivity, repeatability, reproducibility and stability, and owns broad application prospects in the detection of practical water samples. The proposed bismuth-based polyoxometalate fabricated electrochemical sensor exhibits good performance towards the heavy metal ions detection, which may benefit the further application in practical fields.

Hydrogels of PANI doped with Fe3O4 and GO for highly stable sensor for sensitive and selective determination of heavy metal ions

Heavy metal ion (HMI) pollution is threat to human health and environment. Here, a sensor for the electrochemical detection (ECD) of Pb+2 along with simultaneous detection of Cd+2, Cu+2 and Hg+2 utilizing the synergic effect of dopants like graphene-oxide (GO) and iron oxide (Fe3O4) into hydrogels of polyaniline (H-PANI/Fe-GO) displays an excellent square wave anodic stripping voltammetry (SWASV) performance towards Pb+2, with an impressive limit of detection (LOD) of 5.15 nM. The oxidative peaks were observed for simultaneous detection at −0.7306, −0.4899, −0.0092 and 0.3417 V vs. Ag/AgCl for Cd+2, Pb+2, Cu+2 and Hg+2 with good sensitivity, reproducibility and stability. Additionally, H-PANI/Fe-GO sensor is effectively employed to detect Pb+2 in real water samples.

Live synthesis of selective carbon dots as fluorescent probes for cobalt determination in water with an automatic microanalyzer

A new strategy integrating the straight synthesis of carbon dots (CDs) and their direct use for the determination of heavy metals by means of fluorescence quenching is presented. The proposal consists of a modular analyzer, which includes a low temperature co-fired ceramics (LTCC) microreactor for the synthesis of CDs and a cyclic olefin copolymer (COC) microfluidic platform, which automatically performs a reverse flow injection analysis (rFIA) protocol for the determination of heavy metal ions in water by CD fluorescence quenching. As a proof of concept, nitrogen-doped CDs were synthesized from acrylic acid and ethylenediamine (ED) with quantum yields (QYs) of up to 44%, which are selective to cobalt. With the described system, we synthesized homogeneous CDs without the need for further purification and with the minimum consumption of reagents, and optimized fluorescence measurements can be performed with freshly obtained luminescent nanomaterials that have not undergone decomposition processes. They have an average hydrodynamic diameter of 4.2 ± 0.9 nm and maximum excitation and emission wavelengths at 358 nm and 452 nm, respectively. The system allows the automatic dilution and buffering of the synthesized CDs and the sample prior to the determination of cobalt. The concentration of cobalt was determined with good sensitivity and a limit of detection of 7 μg·L−1 with a linear range of 0.02–1 mg·L−1 of Co2+. Spiked tap water and river water samples were analyzed, obtaining recovery from 98 to 104%. This demonstrates the potential of the equipment as an efficient on-site control system for heavy metal monitoring in water.Graphical abstract

Fabrication of Aptamer-based Field Effect Transistor Sensors for Detecting Mercury Ions

With the rapid development of industry, the pollution of the environment is becoming more and more serious. Among them, water pollution is one of the most serious problems, and polluted water sources often contain heavy metal ions such as mercury, chromium, lead, chromium, arsenic, etc. Which in turn affect our irrigation, breeding, food, and drinking, and finally cause physical harm. Mercury is still widely used today. For example, mercury and mercury compounds are used as catalysts in the plastics industry. Mercury is still widely used today. For example, mercury and mercury compounds are used as catalysts in the plastics industry. Some toxic pesticides also contain mercury. Mercury is used in daily life in fluorescent lamps, batteries, thermometers, medical amalgams, etc.Mercury pollution can be divided into two categories: organic mercury and inorganic mercury. Prolonged exposure to mercury can cause paralysis and a progressive loss of sense of touch, sight, hearing, or taste. Other more common neurological symptoms include memory and balance impairment, insomnia, hand tremors, and behavioral disturbances. Detecting the mercury content in water usually requires large-scale laboratory instruments for measurement, costing a lot of money and time.In this study, a specific aptamer is combined with a field-effect transistor to form an aptamer field-effect transistor by utilizing the properties of thymine-Hg(II)-thymine (T-Hg(II)-T) coordination chemical bonds. A highly selective and sensitive mercury ion sensor was achieved by using N-channel depletion-mode MOSFETs with APTAMER-modified gates. For the Aptamer-modified FET sensor, a detection limit of 0.2 PPM was achieved using a 500 μM × 500 μM gate sensing area. Biosensors realize reduced size, shorter detection speeds, cost savings, and high detection of limit sensors. Therefore, the determination of heavy metal ions in the environment by simple and easy-to-use instruments is of great significance for disease prevention. Figure 1

Electrocatalytic self-assembled multilayer structures based on thiolated Fc-DAB dendrimers: Determination of heavy metal ions by enzymatic inhibition

The development of sensitive and rapid inhibition-based biosensors for monitoring trace levels of heavy metals such as lead and copper ions in environmental samples is of high interest. In this work, we describe the fabrication of HRP sensitive peroxide biosensors based on ferrocenyl thiolated DAB dendrimers as bonding-layer between electrodeposited and colloidal gold nanoparticles and compare their electrocatalytic properties with those of thiolated DAB homologues. The complete electrochemical, kinetic and analytical characterization of these new heavy metals’ inhibition-biosensors are investigated.

Ultrasensitive and Selective Electrochemical Sensor Based on Yttrium Benzenetricarboxylate Porous Coordination Polymer (Y-BTC) for Detection of Pb2+ from Bio-Analytes

Due to industrialization, the presence of heavy metal ions in various sources of drinking water causes damage to the ecosystem. Determination of heavy metal ions is still arduous due to their toxicity and carcinogenic behavior to humankind. The present investigation deals with the development of a novel ultrasensitive electrochemical sensor for the detection of lead (Pb2+) from pesticide and fruit core. Repetitive laboratory-scale aqueous samples have been tested to validate all sensing parameters, it exhibited highly selective behaviour towards Pb2+. Hydrothermally synthesized Yttrium Benzenetricarboxylate (Y-BTC) has been characterized by means of structural, morphological, electrochemical and spectroscopic characterizations and utilized as a sensing material. Y-BTC Sensor’s differential pulse behavior shows affinity towards Pb2+, a detailed sensing mechanism further illustrated by XPS studies, DLS measurements, deformation studies by photoluminescence spectra, and charge transfer resistance obtained from EIS data. The developed Y-BTC sensor showcased an excellent picomolar detection limit of 1 pM. Reliability of developed sensor was confirmed by evaluation of sensitivity (4.4 μA M−1), selectivity (towards Pb2+), repeatability and reproducibility. The proposed sensor would play a vital role in monitoring human health in the upcoming days.

A Model Transfer Method among Spectrometers Based on Improved Deep Autoencoder for Concentration Determination of Heavy Metal Ions by UV-Vis Spectra

Ultraviolet Visible (UV-Vis) spectroscopy detection technology has been widely used in quantitative analysis for its advantages of rapid and non-destructive determination. However, the difference of optical hardware severely restricts the development of spectral technology. Model transfer is one of the effective methods to establish models on different instruments. Due to the high dimension and nonlinearity of spectral data, the existing methods cannot effectively extract the hidden differences in spectra of different spectrometers. Thus, based on the necessity of spectral calibration model transfer between the traditional large spectrometer and the micro-spectrometer, a novel model transfer method based on improved deep autoencoder is proposed to realize spectral reconstruction between different spectrometers. Firstly, two autoencoders are used to train the spectral data of the master and slave instrument, respectively. Then, the hidden variable constraint is added to enhance the feature representation of the autoencoder, which makes the two hidden variables equal. Combined with a Bayesian optimization algorithm for the objective function, the transfer accuracy coefficient is proposed to characterize the model transfer performance. The experimental results show that after model transfer, the spectrum of the slave spectrometer is basically coincident with the master spectrometer and the wavelength shift is eliminated. Compared with the two commonly used direct standardization (DS) and piecewise direct standardization (PDS) algorithms, the average transfer accuracy coefficient of the proposed method is improved by 45.11% and 22.38%, respectively, when there are nonlinear differences between different spectrometers.

In-situ synthesized ZIF-67 graphene oxide (ZIF-67/GO) nanocomposite for efficient individual and simultaneous detection of heavy metal ions

Heavy metals are ubiquitous in water bodies as a result of anthropogenic activities and over time they accumulate in body thus posing serious health problems. Therefore, it is essential to improve sensing performance, for determination of heavy metal ions (HMIs), of electrochemical sensors. In this work, cobalt-derived MOF (ZIF-67) was in-situ synthesized and incorporated onto the surface of graphene oxide (GO) by simple sonication method. The prepared material (ZIF-67/GO) was characterized by FTIR, XRD, SEM, and Raman spectroscopy. Afterwards, a sensing platform was made by drop-casting synthesized composite onto glassy carbon electrode for individual and simultaneous detection of heavy metal ions pollutants (Hg2+, Zn2+, Pb2+, and Cr3+) with estimated detection limits of 2nM, 1nM, 5nM, and 0.6nM, respectively, when determined simultaneously, that are below the permissible limit by World Health Organization. To the best of our knowledge, this is first report of HMIs detection by ZIF-67 incorporated GO sensor which can successfully determine the Hg+2, Zn+2, Pb+2, and Cr+3 ions simultaneously with lower detection limits.

Wattle-Bark-Tannin-Derived Carbon Quantum Dots as Multi-Functional Nanomaterials for Intelligent Detection of Cr6+ Ions, Bio-Imaging, and Fluorescent Ink Applications

Using natural wattle bark tannin, a kind of stable, nontoxic, fluorescent carbon quantum dots (CQDs) was hydrothermally fabricated and applied as a multifunctional fluorescent nanomaterial for the determination of heavy metal ions (Cr6+ and Co2+), bio-imaging, and fluorescent ink applications. The CQDs could be assembled with polyvinyl alcohol (PVA) through hydrogen bonding to yield a composite fluorescent hydrogel that can be integrated with a smartphone to constitute a novel and convenient intelligent detection system for the rapid (10 s) real-time monitoring of Cr6+. Both the CQDs (with 1.37 μM of LOD (limit of detection)) and CQDs-PVA hydrogel (with 3.36 mg/L of LOD) sensing systems produced fast, sensitive, and selective response to Cr6+ based on the internal filtering effect and electron-transfer effect. The practicability of the CQDs-PVA fluorescence sensor was demonstrated by determining tap water and tanning wastewater samples. Based on their satisfactory fluorescence stability and solubility, the CQDs were further used for HeLa-cell imaging and as fluorescent ink for information encryption. When HeLa cells were incubated for 24 h in CQDs at a high concentration of 200 mg/L, the cell survival remained as high as 90%, and a clear fluorescence image was observed under a laser confocal fluorescence microscope. The CQD solution could be written directly as fluorescent ink on TLC (thin layer chromatography) paper, and the handwritings were invisible after drying, confirming their application potential in the field of information encryption. In summary, the present CQDs derived from wattle bark tannin exhibited excellent stability, sensitivity, and specificity in heavy metal ion sensing and also had great potential in bio-imaging and information encryption applications.

A portable microfluidic electrochemical sensing platform for rapid detection of hazardous metal Pb2+ based on thermocapillary convection using 3D Ag-rGO-f-Ni(OH)2/NF as a signal amplifying element

Heavy metal pollution is causing a great threat to ecological environment and public health, which needs an efficient strategy for monitoring. A portable microfluidic electrochemical sensing system was developed for the determination of heavy metal ions. Herein, the detection of Pb2+ was chosen as a model, and a microfluidic electrochemical sensing chip relying on a smartphone-based electrochemical workstation was proposed for rapid detection Pb2+ with the assistance of thermocapillary convection result from the formed temperature gradient. The 3D Ag-rGO-f-Ni(OH)2/NF composites, prepared by one-step hydrothermal method without any Ni precursor salt, were used to further amplify electrochemical signals under the synergistic effect of thermocapillary convection. The thermocapillary convection could accelerate the preconcentration process and shorten the detection time (save 300 s of preconcentration time). The fabricated system exhibited the exceptional competence for monitoring of Pb2+ range from 0.01 μg/L to 2100 μg/L with a low detection limit (LOD) of 0.00464 μg/L. Furthermore, this portable system has been successfully demonstrated for detecting Pb2+ (0.01 μg/L to 2100 μg/L) in river water (LOD = 0.00498 μg/L), fish (LOD = 0.00566 μg/L) and human serum samples (LOD = 0.00836 μg/L), and the results were consistent with inductively coupled plasma-mass spectrometry (ICP-MS). The proposed novel sensing platform provides a cost-effectiveness, rapidly responding and ease-to-use pathway for analysis of heavy metal ions in real samples and shows great potential in point-of-care testing.

Biochar from coffee husks: a green electrode modifier for sensitive determination of heavy metal ions

Biochar from coffee husks: a green electrode modifier for sensitive determination of heavy metal ions

Sensitive, Selective and Simultaneous Monitor of Multiple Heavy Metals in Environment Using a Low-Cost MIL-53(Fe)/Ag2CrO4 Modified GCE Sensor

Due to the strong toxicity of heavy metal ions to public health and the environment, it is a great challenge to develop a method for ultra sensitive capture and determination of heavy metal ions effectively. Herein, a novel heterostructure composite (MIL-53(Fe)/Ag2CrO4, named MA(1:x)) was prepared by a simple method successfully. MA(1:x) modified GCE was applied to detect heavy metals ions simultaneously. Significantly, the designed MA(1:1)/GCE sensors performed outstanding detection performances. The wide ranges of 7.49 ∼ 320.00 μmol l−1 and 7.49 ∼ 320.04 μmol l−1 are obtained for Pb(II) and Cu(II) ions, respectively. The LOD of the MA(1:1)/GCE sensor was determined to be 27.40 nmol l−1 (5.68 ppb) for Pb(II) and 86.96 nmol l−1 (5.52 ppb) for Cu(II) ion simultaneously, which are lower than the allowable level of drinking water stipulated by the World Health Organization (WHO). Possible detection mechanism by the MA(1:1)/GCE was discussed. The MA(1:1)/GCE was successfully applied to monitor heavy metal ions locate in tap and river water. The recoveries are in the range of 93.86%–104.4%, which further proves the potential in analyzing real samples. Moreover, the MA(1:1)/GCE also showed excellent stability, selectivity, reproducibility. A novel method was provided to construct sensitive sensors for simultaneous analysis of different metal ions.

Thiacalix[4]arene-based complex with Co(II) ions as electrode modifier for simultaneous electrochemical determination of Cd(II), Pb(II), and Cu(II).

A complex [Co4(TCTA)2(H2O)8]∙10H2O (Co-TCTA) based on thiacalix[4]arene derivative has been synthesized for the first time using the solvothermal method. The glassy carbon electrode (GCE) modified with Co-TCTA (Co-TCTA/GCE) could simultaneously determine Cd2+, Pb2+, and Cu2+ at around - 0.75V, - 0.60V, and - 0.10V (vs. ref. Ag/AgCl) and had good stability, selectivity, and reproducibility with relative standard deviation (RSD) of 4.4% for Cd2+, 1.4% for Pb2+, and 5.4% for Cu2+. Co-TCTA/GCE showed wide linear range of 0.4-8.0μM for Cd2+, 0.4-7.0μM for Pb2+, and 0.6-6.0μM for Cu2+ when three ions were determined simultaneously. The limits of detection (LODs) of Cd2+, Pb2+, and Cu2+ were 0.071μM, 0.022μM, and 0.021μM, respectively. Moreover, the sensor was used to determine three ions in lake water sample with satisfactory recoveries of 93.6-93.8% for Cd2+, 93.8-103.3% for Pb2+ and 94.6-95.3% for Cu2+. The good adsorption capacity of Co-TCTA and Co(II)/Co(0) circular mechanism on the surface of the electrode were proposed to enhance the electrochemical signals. This work enriched the theoretical research on the complexes for the determination of heavy metal ions.

Simultaneous electro-determination of trace copper, lead, and cadmium in tap water by using silver nanoparticles and graphene nanoplates as nanocomposite modified graphite electrode

This study provides a sensitive platform based on silver nanoparticles/graphene nanoplates modified graphite electrode (AgNPs/GrNPs/GE) for the simultaneous and selective voltammetric determination of heavy metal ions in tap water, including such Cd (II), Cu (II), and Pb (II). The as-prepared graphite electrodes were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and field emission scanning electron microscopy (FESEM) experiments. Furthermore, square wave anodic stripping voltammetry (SWASV) was performed to determine the cations mentioned above on the AgNPs/GrNPs/GE surface. Moreover, experimental parameters affecting the simultaneous determination of target metal ions were thoroughly tuned and optimized. When the suggested electrochemical sensor was performed under optimal conditions, detection limits of 5.0, 4.1, and 1.0 ng L−1 were obtained for Cd (II), Cu (II), and Pb (II), respectively. The electrode could also detect Zn (II) and Hg (II), around −1.13 and +0.05 V, respectively. The results revealed that the developed electrochemical sensor has high practical applicability, reproducibility and stability in detecting heavy metal ions.