Development of an enzymeless biosensor for the determination of phenolic compounds

The construction of amperometric enzymeless biosensors for phenolic compounds determination, using carbon paste electrode modified with copper phtalocyanine (CuPc) and histidine (His), based on the chemistry of the dopamine β-monooxygenase (DβM) enzyme that catalyzes the hydroxylation of the dopamine and its analogs is shown. The modified carbon paste was evaluated on electrodes constructed in two ways: putting the paste into a cavity of a rotating disk electrode and a platinum slide electrode fixed into a glass tube. The sensor in hydrodynamic conditions presented a linear response range between 30 and 250 μmol l⁻¹, with a sensitivity of 4.6±0.1 nA l μmol⁻¹ cm⁻² for catechol, response time of 3 s and lifetime of about 50 days when stored at room temperature. The sensor in static conditions showed a linear response range from 40 to 250 μmol l⁻¹, with a sensitivity of 0.30±0.01 nA l μmol⁻¹ cm⁻² for catechol. The sensors presented the following relative response order for dopamine and some analog species: catechol>dopamine>guaiacol>serotonin>phenol.     

Immobilization of [Cu(bpy)2]Br2 complex onto a glassy carbon electrode modified with α-SiMo12O40 and single walled carbon nanotubes: Application to nanomolar detection of hydrogen peroxide and bromate

A simple procedure has been used for preparation of modified glassy carbon electrode with carbon nanotubes and copper complex. Copper complex [Cu(bpy)₂]Br₂ was immobilized onto glassy carbon (GC) electrode modified with silicomolybdate, α-SiMo₁₂O₄₀⁴⁻ and single walled carbon nanotubes (SWCNTs)_. Copper complex and silicomolybdate irreversibly and strongly adsorbed onto GC electrode modified with CNTs. Electrostatic interactions between polyoxometalates (POMs) anions and Cu-complex, cations mentioned as an effective method for fabrication of three-dimensional structures. The modified electrode shows three reversible redox couples for polyoxometalate and one redox couple for Cu-complex at wide range of pH values. The electrochemical behavior, stability and electron transfer kinetics of the adsorbed redox couples were investigated using cyclic voltammetry. Due to electrostatic interaction, copper complex immobilized onto GC/CNTs/α-SiMo₁₂O₄₀⁴⁻ electrode shows more stable voltammetric response compared to GC/CNTs/Cu-complex modified electrode. In comparison to GC/CNTs/Cu-complex the GC/CNTs/α-SiMo₁₂O₄₀⁴⁻ modified electrodes shows excellent electrocatalytic activity toward reduction H₂O₂ and BrO₃⁻ at more reduced overpotential. The catalytic rate constants for catalytic reduction hydrogen peroxide and bromate were 4.5(±0.2) × 10³ M⁻¹ s⁻¹ and 3.0(±0.10) × 10³ M⁻¹ s⁻¹, respectively. The hydrodynamic amperommetry technique at 0.08 V was used for detection of nanomolar concentration of hydrogen peroxide and bromate. Detection limit, sensitivity and linear concentration range proposed sensor for bromate and hydrogen peroxide detection were 1.1 nM and 6.7 nA nM⁻¹, 10 nM-20 μM, 1 nM, 5.5 nA nM⁻¹ and 10 nM-18 μM, respectively.     

Fast analysis of terbutaline in pharmaceuticals using multi-walled nanotubes modified electrodes from recordable compact disc

In this study, homemade disposable gold electrodes made from recordable compact disks were modified with carbon nanotubes for amperometric quantification of terbutaline sulfate in pharmaceutical products. A flow cell using an impingent jet of solution on the electrode surface was build and used for amperometric detection, and a series of experiments were carried out to find the best experimental conditions for the new electrode in a specially designed cell. A linear response for terbutaline was obtained in the range from 3.0 × 10⁻⁶ to 5.0 × 10⁻⁴ mol L⁻¹ (at 0.63 V vs. Ag/AgCl). The limits of detection and quantification were calculated as 5.8 × 10⁻⁷ mol L⁻¹ (S/N = 3) and 1.9 × 10⁻⁶ mol L⁻¹ (S/N = 10), respectively. A frequency of 30 injections h⁻¹ was attained. The proposed method was successfully applied to the analyses of commercial syrup samples, and all results were in good agreement with those obtained by using high performance liquid chromatography and capillary electrophoresis-tandem mass spectrometry.     

Pulsed amperometric detection at glassy carbon electrodes: A new waveform for sensitive and reproducible determination of electroactive compounds

In this work, the application of a new pulsed amperometric detection (PAD) waveform at a glassy carbon electrode, operating in typical chromatographic mobile phases, is proposed for the sensitive and reproducible determination of arylethanolaminic and phenolic moiety based compounds (e.g. beta-agonists and polyphenols). Preliminary experiments by cyclic voltammetry were carried out to investigate the electrochemical behaviour and to select the detection and cleaning electrode potentials. The proposed potential-time profile was designed to prevent the carbon electrode fouling under repeated analyses, thus ensuring a reproducible and sensitive quantitative determination, without the need of any mechanical or chemical electrode cleaning procedure. The waveform electrochemical parameters, including detection and delay times, were optimized in terms of sensitivity, limit of detection and response stability. The optimized waveform allowed the sensitive and stable detection of model compounds, such as clenbuterol and caffeic acid, that showed detection limits of 0.1 μg L⁻¹ and 14 μg L⁻¹, quantification limits of 0.4 μg L⁻¹ and 46 μg L⁻¹, and linearity up to 100 μg L⁻¹ (r = 0.9993) and 10 mg L⁻¹ (r = 0.9998), respectively. Similar results were obtained for other compounds of the same classes, with precision values under repeatability conditions ranging from 3.0 to 5.9%. The proposed method can be then considered as an excellent alternative to the post-column detection of beta-agonists, phenols and polyphenols.     

A novel procedure for rapid surface functionalisation and mediator loading of screen-printed carbon electrodes

We report a simple and rapid procedure that leads to incorporation of mediator and introduction of amine functionality onto the surface of screen-printed carbon electrodes (SPCE). The electrodes were doped with cobalt phthalocyanine (CoPc) by enhanced adsorption in a process that uses minimal amounts of this redox mediator as compared with CoPc loaded inks. The CoPc-doped SPCE showed a substantially increased sensitivity to hydrogen peroxide and thiocholine as compared to unmodified electrodes. This greatly facilitated their use as transducers for the construction of amperometric biosensors based on enzymes producing oxidizable products such as hydrogen peroxide or thiols. Immobilisation of enzymes including glucose oxidase, acetylcholinesterase and choline oxidase was achieved through their multi-contact electrostatic interaction with polyethyleneimine (PEI) which was electrodeposited on the surface of CoPc-doped electrodes in one step from ethanolic solution. The efficiency of enzyme immobilisation was shown to depend on the molecular weight of the PEI used, reaching a maximum for 25 kDa PEI. The biosensors shown sensitivity to glucose at 130 nA mM⁻¹ (LOD 0.15 mM) and to acetylcholine at 70 nA mM⁻¹ (LOD 0.10 mM) under +0.6 V. Detection of glucose has been demonstrated at +0.4 V with the sensitivity of 60 nA mM⁻¹ and LOD of 0.33 mM. Possibility of the inhibition analysis of pesticides has been shown for acetylcholinesterase-based sensors.     

Cobalt(II) and nickel(II) complexes of a cyclam derivative as carriers in iodide-selective electrodes

The ligand 1,4,8-tri(n-octyl)-1,4,8,11-tetraazacyclotetradecane (L¹) containing pendant octyl groups has been synthesised. L¹ is a tetraazamacrocycle derived from the well-known cyclam unit, and the Ni²⁺ and Co²⁺ complexes, [Ni(L¹)]²⁺ and [Co(L¹)]²⁺, have been isolated and characterised. The ability of the nickel(II) and cobalt(II) complexes to act as anion receptors has been studied by using them as ionophores in membrane-based ion-selective electrodes (ISEs). The PVC membrane containing the complex [Ni(L¹)]²⁺ and 2-nitrophenyloctylether as plasticizer shows a Nernstian response against iodide in a concentration range from 1×10⁻¹ to 4×10⁻⁵ M I⁻ with a detection limit of 1.6×10⁻⁵ M I⁻ and a slope of 58.6 mV/pI⁻ at pH 7 (25 °C). In comparison, the electrode containing [Co(L¹)]²⁺ as ionophore gave a sub-Nernstian slope and a low lifetime. A comparison between the iodide-selective electrode containing [Ni(L¹)]²⁺ and other reported iodide-selective electrodes is also reported.     

On-site fuel electroanalysis: Determination of lead,copper and mercury in fuel bioethanol by anodic stripping voltammetry using screen-printed gold electrodes

The potential application of commercial screen-printed gold electrodes (SPGEs) for the trace determination of lead, copper, and mercury in fuel bioethanol is demonstrated. Samples were simply diluted in 0.067 mol L⁻¹ HCl solution prior to square-wave anodic stripping voltammetry (SWASV) measurements recorded with a portable potentiostat. The proposed method presented a low detection limit (<2 μg L⁻¹) for a 240 s deposition time, linear range between 5 and 300 μg L⁻¹, and adequate recovery values (96–104%) for spiked samples. This analytical method shows great promise for on-site trace metal determination in fuel bioethanol once there is no requirement for sample treatment or electrode modification.     

Amperometric Glucose Biosensor Based on Electrochemically Deposited Gold Nanoparticles Covered by Polypyrrole

Graphite rod (GR) modified with electrochemicaly deposited gold nanoparticles (AuNPs) and adsorbed glucose oxidase (GOx) was used in amperometric glucose biosensor design. Enzymatic formation of polypyrrole (Ppy) on the surface of GOx/AuNPs/GR electrode was applied in order to improve analytical characteristics and stability of developed biosensor. The linear glucose detection range for Ppy/GOx/AuNPs/GR electrode was dependent on the duration of Ppy‐layer formation and the linear interval was extended up to 19.9 mmol L⁻¹ after 21 h lasting synthesis of Ppy. The sensitivity of the developed biosensor was determined as 21.7 μA mM⁻¹ cm⁻², the limit of detection – 0.20 mmol L⁻¹. Ppy/GOx/AuNPs/GR electrodes demonstrated advanced good stability (the t _1/2 was 9.8 days), quick detection of glucose (within 5 s) in the wide linear interval. Additionally, formed Ppy layer decreased the influence of electroactive species on the analytical signal. Developed biosensor is suitable for the determination of glucose in human serum samples.     

Cobalt oxide nanostructure-modified glassy carbon electrode as a highly sensitive flow injection amperometric sensor for the picomolar detection of insulin

Glassy carbon electrode modified with electrodeposited cobalt oxide nanostructure shows an excellent electrocatalytic activity toward insulin oxidation at a wide pH range. Cyclic voltammetry, hydrodynamic amperometry, and flow injection analysis (FIA) were used for insulin determination at a picomolar and higher-concentration range. Amperometric determination of insulin at this modified electrode yielded a calibration curve with the following characteristics; linear range, 100 pM–15 nM; sensitivity of 83.9 nA nM⁻¹ and detection limit 10 pM. FIA yielded the calibration curve with sensitivity and detection limit of 2.0 nA nM⁻¹ and 25 pM, respectively. Furthermore, the RSD of repetitive FIA for 200 pM insulin (n = 13) is 2%. In addition, the interference effect of electroactive existing species (lactic acid, cholesterol, ascorbic acid, uric acid, and glucose) was eliminated by covering the surface of the modified electrode with nafion film. Fast response time, signal stability, high sensitivity, low cost, and ease of preparation are the advantages of the proposed insulin sensor.     

Construction of novel simple phosphate screen-printed and carbon paste ion-selective electrodes

The construction and performance characteristics of different phosphate ion-selective electrodes are described. Three types of electrodes are demonstrated, namely screen-printed, carbon paste and the conventional PVC membrane electrodes. The cited electrodes are based on bisthiourea ionophores and show a considerable selectivity towards hydrogenphosphate with Nernstian slopes depending on the type of the electrode and the ionophore used. Matrix compositions of each electrode are optimised on the basis of effects of type and concentration of the ionophore as well as influence of the selected plasticizers. The screen-printed electrodes work satisfactorily in the concentration range 10⁻⁵ to 10⁻² mol L⁻¹ with anionic Nernstian compliance (32.8 mV/decade activity) and detection limit 4.0 × 10⁻⁶ mol L⁻¹. The screen-printed electrodes show fast response time of about 2.2 s and exhibit adequate shelf-life (4 months). The fabricated electrodes can be also successfully used in the potentiometric titration of HPO₄²⁻ with Ba²⁺.     

Enhanced sensitivity for Cu(II) by a salicylidine-functionalized polysiloxane carbon paste electrode

A new approach for decreasing the detection limit for a copper(II) ion-selective electrode (ISE) is presented. The ISE is designed using salicylidine-functionalized polysiloxane in carbon paste. This work describes the attempts to develop the electrode and measurements of its characteristics. The new type of renewable three-dimensional chemically modified electrode could be used in a pH range of 2.3–5.4, and its detection limit is 2.7 × 10⁻⁸ mol L⁻¹ (1.2 μg L⁻¹). This sensor exhibits a good Nernstian slope of 29.4 ± 0.5 mV/decade in a wide linear concentration range of 2.3 × 10⁻⁷ to 1.0 × 10⁻³ mol L⁻¹ of Cu(II). It has a short response time (8 s) and noticeably high selectivity over other Cu(II) selective electrodes. Finally, it was satisfactorily used as an indicator electrode in complexometric titration with EDTA and determination of copper(II) in miscellaneous samples such as urine and various water samples.     

Synergy between Printex nano-carbons and silver nanoparticles for sensitive estimation of antioxidant activity

We report on the synthesis, characterization and applications of a Printex L6 carbon-silver hybrid nanomaterial (PC-Ag), which was obtained using a polyol method. In addition, we also highlight the use of Printex L6 nano-carbon as a much cheaper alternative to the use of carbon nanotubes and graphene. The silver nanoparticles (AgNP) were prepared directly on the surface of the Printex 6L carbon “nanocarbon” material using ethylene glycol as the reducing agent. The hybrid nanomaterial was characterized by High-angle annular dark-field transmission electron microscopy (HAADF-TEM), energy–dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), Raman spectroscopy and cyclic voltammetry. Optimized electrocatalytic activity on glassy carbon electrode was reached for the architecture GC/PC-Ag, the silver nanoparticles with size ranging between 1 and 2 nm were well–distributed throughout the hybrid material. The synergy between PC nano-carbons and AgNPs was verified by detection of gallic acid (GA) at a low applied potential (0.091 V vs. Ag/AgCl). GA detection was performed in a concentration range between 5.0 × 10⁻⁷ and 8.5 × 10⁻⁶ mol L⁻¹, with a detection limit of 6.63 × 10⁻⁸ mol L⁻¹ (66.3 nmol L⁻¹), which is considerably lower than similar devices. The approach for fabricating the reproducible GC/PC-Ag electrodes is entirely generic and may be explored for other types of (bio)sensors and devices.     

A new method for electrocatalytic oxidation of ascorbic acid at the Cu(II) zeolite-modified electrode

A new method is developed for the catalytic oxidation of ascorbic acid at graphite zeolite-modified electrode, doped with copper(II) (Cu²⁺A/ZCME). Copper(II) exchanged in zeolite type A acts as catalyst to oxidize ascorbic acid. The modified electrode lowered the overpotential of the reaction by ∼400 mV. First, the electrochemical behavior of copper(II), incorporated in the zeolite type A modified electrode, was studied. The results illustrate that diffusion can control the copper(II)/copper(0) redox process at the Cu²⁺A/ZCME. Then, the behavior of electrocatalytic oxidation reaction for ascorbic acid was researched. The electrode was employed to study electrocatalytic oxidation of ascorbic acid, using cyclic voltammetry and chronoamperometry as diagnostic techniques. The diffusion coefficient of ascorbic acid was equal to 1.028 × 10⁻⁵ cm² s⁻¹. A linear calibration graph was obtained over the ascorbic acid with a concentration range of 0.003-6.00 mmol L⁻¹. The detection limit (DL) of ascorbic acid was estimated as 2.76 × 10⁻⁷ mol L⁻¹. The relative standard deviations of 10 replicate measurements (performed on a single electrode at several ascorbic acid concentrations between 3.0 and 200 μmol L⁻¹) were measured between 1.0 and 2.4%.     

Simultaneous determination of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) in food samples using a carbon composite electrode modified with Cu3(PO4)2 immobilized in polyester resin

A simple electrochemical method was developed for the single and simultaneous determination of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) in food samples using square-wave voltammetry (SWV). A carbon composite electrode modified (MCCE) with copper (II) phosphate immobilized in a polyester resin was proposed. The modified electrode allowed the detection of BHA and BHT at potentials lower than those observed at unmodified electrodes. A separation of about 430 mV between the peak oxidation potentials of BHA and BHT in binary mixtures was obtained. The calibration curves for the simultaneous determination of BHA and BHT demonstrated an excellent linear response in the range from 3.4 × 10⁻⁷ to 4.1 × 10⁻⁵ mol L⁻¹ for both compounds. The detection limits for the simultaneous determination of BHA and BHT were 7.2 × 10⁻⁸ and 9.3 × 10⁻⁸ mol L⁻¹, respectively. In addition, the stability and repeatability of the electrode were determined. The proposed method was successfully applied in the simultaneous determination of BHA and BHT in several food samples, and the results obtained were found to be similar to those obtained using the high performance liquid chromatography method with agreement at 95% confidence level.     

Linear polyamines as carriers in thiocyanate-selective membrane electrodes

The polyamines, octyl-[2-(2-octylamino-ethylamino)-ethyl]-amine (L¹) and octyl-{2-[2-(2-octylamino-ethylamino)-ethylamino]-ethyl}-amine (L²), have been used as anion ionophores in PVC-based membrane ion-selective electrodes. Different electrodes were prepared containing L¹, or L², and o-nitrophenyl octyl ether (NPOE) or bis(2-ethylhexyl)sebacate (DOS) as plasticizers. The response of the electrodes was tested in two different buffers, HEPES-KOH (pH 7) and MES-KOH (pH 5.6). Electrodes containing L¹ and L² with NPOE (E1 and E2, respectively) showed a Nernstian response for thiocyanate with a good response time. The detection limit, linear range and slope for electrode E1 were 3.8 × 10⁻⁶ mol dm⁻³, 1 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −57.2 mV decade⁻¹ at pH 5.6 and 4.47 × 10⁻⁶ mol dm⁻³, 1.95 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −58.1 mV decade⁻¹ at pH 7.0. For electrode E2 the detection limit, linear range and slope found were 2.63 × 10⁻⁶ mol dm⁻³, 7.94 × 10⁻⁶ to 1 × 10⁻¹ mol dm⁻³ and −58.5 mV decade⁻¹ at pH 5.6 and 1.23 × 10⁻⁵ mol dm⁻³, 7.95 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −46.0 mV decade⁻¹ at pH 7. In contrast, electrodes containing DOS as plasticizers gave only response at pH 5.6 (detection limit, linear range and slope at pH 5.6 were 3.16 × 10⁻⁵ mol dm⁻³, 1 × 10⁻⁴ to 1 × 10⁻¹ mol dm⁻³ and −52.6 mV decade⁻¹). Selectivity coefficients for different anions with respect to thiocyanate were calculated. The electrode E2 at pH 5.6 was also used for the determination of SCN⁻ by potentiometric titrations with Ag⁺ ions with good results. The electrode E2 was also used to determine concentrations of thiocyanate in biological samples.     

The petentiometric determination of peroxide hydrogen and glucose on the glassy electrode modified by the calix[4]arene

A new petentiometric method to determine peroxide hydrogen and glucose had been studied. This method had been applied on the petentiometric determination of peroxide hydrogen and glucose in the total ionic strength adjustment buffer (TISAB) (pH 7.5) solution with the glassy electrode modified by the calix[4]arene. The glassy carbon electrode covered with the calix[4]arene depended on the H₂O₂ concentration in the range of log[H₂O₂] from −3.3 to −1.2 in the solution of TISAB (pH 7.5) with nearly Nernstian slope of about 65.6 ± 3 mV and the detection limit of peroxide hydrogen was 4.0 × 10⁻⁵ mol L⁻¹. The glassy carbon electrode covered with the calix[4]arene depended on the glucose concentration in the range of log[glucose] from −3.6 to −2.8 in the solution of TISAB (pH 7.5) with nearly Nernstian slope of about 50.2 ± 2 mV and the detection limit of glucose was 2.0 × 10⁻⁵ mol L⁻¹. The electrode had the good selectivity, sensitivity, stability and repeatability.     

Sensitive and stable monitoring of lead and cadmium in seawater using screen-printed electrode and electrochemical stripping analysis

Sensitive and stable monitoring of heavy metals in seawater using screen-printed electrodes (SPE) is presented. The analytical performance of SPE coupled with square wave anodic stripping voltammetry (SWASV) for the simultaneous determination of Pb and Cd in seawater samples, in the low μg L⁻¹ range, is evaluated. The stripping response for the heavy metals following 2 min deposition was linear over the concentration range examined (10-2000 μg L⁻¹) with detection limits of 1.8 and 2.9 μg L⁻¹ for Pb and Cd, respectively. The accuracy of the method was validated by analyzing metal contents in different spiked seawater samples and comparing these results to those obtained with the well-established anodic stripping voltammetry using the hanging mercury drop electrode. Moreover, a certified reference material was also used and the results obtained were satisfactory.     

Electrodes with extremely high hydrogen overvoltages as substrate electrodes for stripping analysis based on bismuth-coated electrodes

Hydrogen evolution bothers stripping analysis significantly. Dioctyl phthalate-based carbon paste electrode exhibits extremely wide cathodic potential window. It is explored as a powerful substrate electrode to solve the problem of hydrogen evolution and further improve reproducibility for stripping analysis using bismuth-coated electrodes for the first time. It was successfully applied to the simultaneous determination of Zn²⁺, Cd²⁺, and Pb²⁺. Linear responses are obtained for Zn²⁺ in the range of 10–100 μg L⁻¹ and for Pb²⁺ and Cd²⁺ in the range of 5–100 μg L⁻¹. The detection limits for Zn²⁺, Cd²⁺, and Pb²⁺ are 0.1 μg L⁻¹, 0.22 μg L⁻¹ and 0.44 μg L⁻¹, respectively. The method has been successfully applied to the determination of Zn²⁺, Cd²⁺, and Pb²⁺ in waste water samples. The detection strategy based on the combination of dioctyl phthalate-based carbon paste electrode and bismuth-coated electrodes holds great promise for stripping analysis.     

Composite planar electrode for sensing electrochemical oxygen demand

This work reports on the development of a graphite-polystyrene composite electrode of planar configuration, containing silver(II) oxide and copper(II) oxide catalysts (AgO-CuO), for the measurement of electrochemical oxygen demand (EOD). Optimisation studies of the composite composition as well as conditions for its processing on planar substrates and generation of an appropriate electrochemical active area resulted in the scalable fabrication of robust composite electrodes. These were evaluated with glucose as target analyte. They showed competitive low limits of detection in a linear concentration range from 5 mg L⁻¹ to 1400 mg L⁻¹ of O₂. Besides, they were stable for at least one year. The determination of EOD in wastewater samples coming from production lines of parenteral food and winemaking was successfully carried out.     

Synthesis of a novel electrode material containing phytic acid-polyaniline nanofibers for simultaneous determination of cadmium and lead ions

The development of nanostructured conducting polymers based materials for electrochemical applications has attracted intense attention due to their environmental stability, unique reversible redox properties, abundant electron active sites, rapid electron transfer and tunable conductivity. Here, a phytic acid doped polyaniline nanofibers based nanocomposite was synthesized using a simple and green method, the properties of the resulting nanomaterial was characterized by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A glassy carbon electrode modified by the nanocomposite was evaluated as a new platform for the simultaneous detection of trace amounts of Cd²⁺ and Pb²⁺ using differential pulse anodic stripping voltammetry (DPASV). The synergistic contribution from PANI nanofibers and phytic acid enhances the accumulation efficiency and the charge transfer rate of metal ions during the DPASV analysis. Under the optimal conditions, good linear relationships were obtained for Cd²⁺ in a range of 0.05–60 μg L⁻¹, with the detection limit (S/N = 3) of 0.02 μg L⁻¹, and for Pb²⁺ in a range of 0.1–60 μg L⁻¹, with the detection limit (S/N = 3) of 0.05 μg L⁻¹. The new electrode was successfully applied to real water samples for simultaneous detection of Cd²⁺ and Pb²⁺ with good recovery rates. Therefore, the new electrode material may be a capable candidate for the detection of trace levels of heavy metal ions.