Selective Voltammetric Sensor Research Articles

Self-assembly of simple Schiff base ligand into unique saddle-type [4x4] tetranuclear architecture and its application as selective voltammetric dopamine sensor in aqueous conditions

Dopamine, a crucial catecholamine neurotransmitter, plays essential roles in the operation of the central nervous system in humans. Disrupted dopamine release is associated with neurological disorders and depression, therefore monitoring of dopamine levels is imperative for preliminary disease detection. Development of sensitive and selective sensors for neurotransmitters that function under aqueous conditions is however still challenging, mostly due to the complexity of hybrid nanomaterials that are interacting with the electrode. Here we provide a coordination compound constructed from simple substrates, where subcomponent self-assembly leads to a unique, discrete [4 × 4] saddle-type complex [Cu4(L-H)4(BF4)2(MeOH)2](BF4)2, which was characterized by ESI-MS and FT-IR techniques, including single crystal X-ray diffraction. The Cu4L4 complex was subsequently used for modification of the bare Au electrode based on its accumulation on the electrode surface. The new voltammetric sensor (Au/complex) was applied for dopamine detection alone and in the presence of interfering ascorbic acid by using the Differential Pulse Voltammetry (DPV) techniques under aqueous conditions. In the linear dynamic range (LDR) range from 0.0001 mM to 0.75 mM the dependence of the peak current on dopamine concentration satisfied the following linear regression equation: ip [mA] = 17∙10−2cDA [mM] + 8∙10−2 (R2 = 0.998). Moreover, the excellent limit of dopamine detection (LOD) and the limit of its quantification (LOQ) were established at the level of 5.4 nM and 18.0 nM with accomplished high sensitivity 0.17 A M−1, repeatability as well as reproducibility. Clear separation of the voltammetric signal of dopamine from this one of ascorbic acid, even in the presence of a 100-fold excess of interfering ions found in water, consequently proves that the new prepared sensor can be used as an excellent analytical tool for selective detection of dopamine and ascorbic acid coexisting in the tested samples.

Preparation of an efficient and selective voltammetric sensor based on screen printed carbon ink electrode modified with TiO2 nanoparticles for Azithromycin quantification

The tetragonal (rutile) nanostructures of TiO2 Nanoparticles (TiO2 NPs) have gained importance due to their large active sites, electronic states influencing superior electrode performance, stability and conductivity. In this regard, Screen printed carbon ink electrode modified with TiO2 was proposed as an electrochemical sensor for the quantification of Azithromycin. TiO2 NPs was used as a modifier in order to improve the electrochemical signal of the bare carbon ink used for the screen printed carbon ink electrode (SPCIE). Some other nanostructured materials, such as Multi Walled Carbon Nanotubes (MWCNT) and Graphene Nano Platelets (GNPL), were also studied with the purpose of increasing the current signal of carbon electrode, but they did not show any expected significant effects, or they were mechanically not suitable to be printed as electrode. Azithromycin is one of the top prioritized antibiotics which are widely used by humans; lastly it is one of the most used antibiotics to treat patients with COVID-19 infection. Therefore, the determination of Azithromycin in urine samples as well as in water media is important, because of the implications antibiotics are known to have with health and natural environment. SPCIE bulk-modified with TiO2 NPs was characterized by SEM-EDS analysis. Cyclic voltammetry analysis was used to determine Azithromycin and with all optimized accompanying analytical parameters. The prepared TiO2 NPs/SPCIE electrode showed a limit of detection (LOD) of 0.93 μM with a limit of quantification (LOQ) of 3.1 µM, sensitivity of 7.36 µA µM−1 cm−2 (S/N = 3), and a linearity range of 0.05–50 μM towards determination of Azithromycin standards.

A New Electrochemical Sensor for the Detection of Ketoconazole Using Carbon Paste Electrode Modified with Sheaf-like Ce-BTC MOF Nanostructure and Ionic Liquid.

An ultrasensitive and selective voltammetric sensor with an ultratrace-level detection limit is introduced for ketoconazole (KTC) determination in real samples using a modified carbon paste electrode with a sheaf-like Ce-BTC MOF nanostructure and ionic liquid. The as-synthesized nanostructure was characterized by several techniques, including energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The electrocatalytic performance of the developed electrode was observed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), and chronoamperometry. The limit of detection (LOD) of the developed sensor for KTC is 0.04 μM, and the response was found to be in the dynamic concentration range of 0.1-110.0 μM in a phosphate buffer solution. The proposed electrode exhibits acceptable electrocatalytic activity for KTC oxidation with a high sensitivity of 0.1342 μA·μM-1. The ability of the fabricated sensor to monitor KTC in real aqueous samples is demonstrated using standard addition data.

Selective Voltammetric Sensor for the Simultaneous Quantification of Tartrazine and Brilliant Blue FCF.

Tartrazine and brilliant blue FCF are synthetic dyes used in the food, cosmetic and pharmaceutical industries. The individual and/or simultaneous control of their concentrations is required due to dose-dependent negative health effects. Therefore, the paper presents experimental results related to the development of a sensing platform for the electrochemical detection of tartrazine and brilliant blue FCF based on a glassy carbon electrode (GCE) modified with MnO2 nanorods, using anodic differential pulse voltammetry. Homogeneous and stable suspensions of MnO2 nanorods have been obtained involving cetylpyridinium bromide solution as a cationic surfactant. The MnO2 nanorods-modified electrode showed a 7.9-fold increase in the electroactive surface area and a 72-fold decrease in the electron transfer resistance. The developed sensor allowed the simultaneous quantification of dyes for two linear domains: in the ranges of 0.10-2.5 and 2.5-15 μM for tartrazine and 0.25-2.5 and 2.5-15 μM for brilliant blue FCF with detection limits of 43 and 41 nM, respectively. High selectivity of the sensor response in the presence of typical interference agents (inorganic ions, saccharides, ascorbic and sorbic acids), other food dyes (riboflavin, indigo carmine, and sunset yellow), and vanillin has been achieved. The sensor has been tested by analyzing soft and isotonic sports drinks and the determined concentrations were close to those obtained involving the chromatography technique.

Sensitive and Selective Voltammetric Sensor Based on Anionic Surfactant-Modified Screen-Printed Carbon for the Quantitative Analysis of an Anticancer Active Fused Azaisocytosine-Containing Congener

3-(4-Nitrophenyl)-8-(2,3-dimethylphenyl)-7,8-dihydroimidazo[2,1-c][1,2,4]triazin-4(6H)-one (NDIT) is one of the most promising candidates for anticancer agents. Hence, a sensitive and selective sodium dodecyl sulfate-modified screen-printed carbon sensor (SPCE/SDS) was used for its quantitative analysis. The SPCE/SDS, in contrast to the SPCE, showed excellent behavior in the electrochemical reduction of NDIT by differential-pulse adsorptive stripping voltammetry (DPAdSV). Cyclic voltammetric (CV) studies reveal an irreversible, two-stage and not purely diffusion-controlled reduction process in 0.01 M HNO3. The sensor was characterized by CV and electrochemical impedance spectroscopy (EIS). Under the optimized conditions (t 45 s, ΔE 175 mV, ν 150 mV/s, and tm 5 ms), the DPAdSV procedure with the SPCE/SDS presented a very wide linear range from 1 to 2000 nM and a low detection limit of 0.29 nM. A 1000-fold excess concentration of potential interferents commonly present in biological samples did not significantly alter the peak current of NDIT. The practical application of the proposed DPAdSV procedure with the SPCE/SDS was successfully checked by analyzing spiked human serum samples.

A Novel Synthesis of a Magnetic Porous Imprinted Polymer by Polyol Method Coupled with Electrochemical Biomimetic Sensor for the Detection of Folate in Food Samples

The present study reports the development and application of a novel, sensitive, and selective voltammetric sensor for the quantitation of folate or vitamin B9 in foodstuffs. The sensor was made from magnetic molecularly imprinted polymers (MMIPs), which were synthesized by the core–shell method using magnetite nanoparticles obtained by the polyol method. The MMIP-based sensor was used for the selective and specific detection of folate in different food samples. The MMIP material was constructed using magnetic water-dispersible nanomaterial, which was prepared by immersing iron (III) acetylacetonate in tri-ethylene-glycol (TEG) solvent. The magnetic water-dispersible nanomaterial was then subjected to polymerization using allyl alcohol as a functional monomer, ethylene-glycol-dimethacrylate (EGDMA) as a cross-linking agent, and 2,2-Azobisisobutyronitrile (AIBN) as a radical initiator. The proposed magnetic materials were characterized by Brunauer–Emmett–Teller (BET), field emission gun scanning electron microscopy (FEG-SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM) analysis. The quantification of folate was performed by square wave voltammetry under optimized conditions using 15 mg of MMIPs and 85 mg of carbon paste. The modified electrode presented a linear dynamic range (LDR) of 2.0–12 µmol L−1 and a limit of detection (LOD) of 1.0 × 10−7 mol L−1 in 0.1 mol L−1 acetate buffer solution (pH 4.0). The proposed sensor was successfully applied for folate detection in different food samples, where recovery percentages ranging from 93 to 103% were obtained. Finally, the results obtained from the analysis of selectivity showed that the modified biomimetic sensor is highly efficient for folate determination in real food samples. Adsorption tests were used to evaluate and compare the efficiency of the MMIPs and magnetic non-molecularly imprinted polymer (MNIPs)—used as control material, through the application of HPLC as a standard method.

A reusable and sensitive electrochemical sensor for determination of idarubicin in environmental and biological samples based on NiFe2O4 nanospheres anchored N-doped graphene quantum dots composite; an electrochemical and molecular docking investigation

An ultrasensitive and selective voltammetric sensor with ultra-trace level detection limit is introduced for idarubicin (IDA) determination in real samples. The as-synthesized nanocomposite was characterized by several techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, Energy-dispersive X-ray spectroscopy (EDX), and Field emission scanning electron microscopy (FE-SEM). The electrocatalytic performance of the developed electrode was observed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The limit of detection (LOD) of the developed sensor for idarubicin is 1.0 nM, and the response is found to be in the dynamic concentration range of 0.01–1.9 μmol/L in a Britton–Robinson buffer (B-R, pH = 6.0). Moreover, the fabricated electrode illustrated high selectivity with good repeatability and reproducibility for diagnosing idarubicin as an anthracycline antileukemic drug. Furthermore, to evaluate the validity of the recommended method, three real samples, including human plasma, urine, and water samples, were analyzed with satisfactory recovery and compared with high-performance liquid chromatography (HPLC). The minor groove-binding mode of interaction was also supported by docking simulation studies, emphasizing that IDA can bind to ds-DNA preferably and confirmed experimental results. The reduced assay time and the possibility of measuring a single sample with another anticancer drug without any interference are significant advantages compared to the HPLC. The developed and validated sensor could be a valuable point-of-care diagnostic tool for IDA quantification in patients.

Ultra-trace level voltammetric sensor for MB in human plasma based on a carboxylic derivative of Calix[4]resorcinarene capped silver nanoparticles

This work was initiated by synthesizing a carboxylic derivative of Calix[4]resorcinarene through a three step protocol confirmed by proton nuclear magnetic resonance (1H NMR) spectroscopy and Electrospray ionization mass spectroscopy (ESI-MS). As synthesized derivative, was used as reducing and capping material for the fabrication of small and stable silver nanoparticles (AgNPs) in aqueous medium under the combined influence of dilute alkali and heat at 90 °C. These nanoparticles were referred as KM20-AgNPs. Techniques used for characterization of AgNPs include UV–Visible (UV–Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, atomic force microscopy (AFM), dynamic light scattering (DLS) and zeta potential analyzer (ZPA). The finally produced KM20-AgNPs were recognized as highly sensitive and extremely selective voltammetric sensor for low level detection of methylene blue drug in the linear working range of 1–30 nM with limit of detection (LOD) and limit of quantification (LOQ) as 0.16 nM and 0.53 nM respectively. The developed sensor was successfully used for sensing of MB in human blood plasma.

Electrochemical sensor based on Ni-exchanged natural zeolite/carbon black hybrid nanocomposite for determination of vitamin B6

The utilization of environmentally friendly nanoporous natural zeolite exchanged with Ni2+ ions (NiZ) and conductive carbon black (CB) in the fabrication of a novel and selective voltammetric sensor of vitamin B6 (VB6) is presented. The used clinoptilolite-rich zeolite material and CB were characterized in terms of morphology and textural properties. The superior properties of Ni-zeolite/carbon black modified glassy carbon electrode (NiZCB-GCE), arising from the synergistic effect of combining the unique features of zeolite and conductive carbon black, were confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. In the determination of VB6 with the use of differential pulse voltammetry (DPV), the optimization of the pH value of supporting electrolyte and instrumental parameters, as well as the interference study were performed. Under optimized conditions, the oxidation peak current at the potential +0.72 V vs. Ag | AgCl | 3 M KCl reference electrode was linear to the VB6 concentration in the range 0.050 to 1.0 mg L−1 (0.30–5.9 μmol L−1) (R = 0.9993). The calculated limit of detection (LOD, S/N = 3), equal to 15 μg L−1 (0.09 μmol L−1), was much better compared to chemically modified electrodes with other carbon-based materials. The RSD for 0.5 mg L−1 was in the range 2.5–5.4% (n = 4). The developed NiZCB-GCE was successfully applied to the determination of VB6 in commercially available multivitamin dietary supplements, food, and water samples. The obtained recoveries ranged from 95 to 106%.Graphical abstract

Sensitive and selective electrochemical detection of vanillin at graphene based poly (methyl orange) modified electrode

Vanillin (VN) is a flavouring substance commonly used in the food and pharmaceutical industry. The rampant use of VN has significant implications on human health. In this work, a sensitive and selective voltammetric sensor to detect VN in food essences and natural vanilla beans was elucidated using a poly(methyl orange) modified graphene paste electrode (PMOMGPE). The surface morphology of PMOMGPE and a bare graphene paste electrode (BGPE) was compared using field emission - scanning electron microscopy (FE-SEM) and electron transfer kinetics were analysed by Electrochemical impedance spectroscopy (EIS). The electrochemical activities of PMOMGPE and BGPE were assessed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in 0.2 M phosphate buffer solution (PBS) of an optimum pH of 6.5 with an accumulation time of 20 s in a potential window of 0.2 V–1 V. Superior electrocatalytic activity was observed by PMOMGPE for the oxidation of VN, which is attributed to the high surface area and interactions between the polymer film and analyte. The VN sensor exhibited a low detection limit of 7.35 × 10−8 M by the DPV method and 20.19 × 10−8 M by the CV method. Various parameters like heterogeneous rate constant (ko = 1.7 × 10−5 cm s−1), number of electrons transferred (n = 2), and surface concentration (Γ = 0.8 nmol cm−2) were calculated. The selectivity of the prepared sensor for VN detection in the presence of common interferents such as metal ions and organic species was noteworthy. PMOMGPE was reliably used for the simultaneous analysis of VN along with indigo carmine (IC) and tartrazine (TZ). This facile VN sensor can be effectively used for real sample analysis, due to its simplicity and stability.

Sensitive and selective voltammetric sensor based on polythiophene nanocomposite mixed MWCNT-G for the determination of Tartrazine

This paper presents a sensitive electrochemical sensor for Tartrazine (Tz) based on polythiophene and mixed Multi-walled carbon nanotube-graphene (PTH/MWCNT-G) via the oxidative polymerization route. The PTH/MWCNT-G was confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR), and the morphology was studied via scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) and transmission electron microscope (TEM) analyses. The scan rate study indicated that the oxidation of Tz under optimum conditions was irreversible with diffusion control. The electrocatalytic activities of the modified electrode were studied by square wave voltammetry (SWV), and the results showed two linear behavior in the range of (1–100 µM) and (250–450 µM) with a limit of detection (LOD) of 0.25 µM and 0.303 µM respectively. The sensor also exhibited high stability and reproducibility. The practical application of the modified electrode was confirmed by the detection of Tz in a soft drink, and the recovery was between 106.7% and 97.87%.

Electroanalytical Performance of Surfactant-Modified Composite Carbon Paste Electrode for the Sensitive and Selective Determination of Fast Sulphon Black F

A sensitive and selective voltammetric sensor was fabricated by incorporating carbon paste into multiwalled carbon nanotubes, followed by drop coating of sodium dodecyl sulfate (SDS), onto the surface in an attempt to find an approachable method for the electrochemical analysis of Fast Sulphon Black F. This equipped SDS-modified composite carbon paste electrode (SDSMCCPE) exhibited an efficient electrocatalytic behavior in the oxidation of FSBF and portrayed a well resolved, irreversible oxidation peak at a potential of 0.716 V, with an enhanced current sensitivity of 34.50 µA in 0.2 M phosphate buffer solution of pH 6.5. The SDSMCCPE and bare composite carbon paste electrode were characterized via field-emission scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode exhibited two dynamic linear ranges between 2-40 and 45-200 µM and a promising detection limit of 2.4 × 10−8 M was found for the first linear range. Thus, the fabricated sensor is a promising methodology for the concurrent determination of FSBF, tartrazine and indigo carmine, and can also be used in the study of the potential interference of synthetic dyes. SDSMCCPE involves a simple fabrication procedure, has a quick response, has admirable stability, is reproducible and has antifouling effects.

Electroanalytical application of thiol-grafted laponite to the sensitive quantification of ciprofloxacin antibiotic

In this study, a sensitive and selective voltammetric sensor was proposed for the detection of ciprofloxacin (CFX) fluoroquinolone-based antibiotic, using a glassy carbon electrode (GCE) modified by a thin film of thiol functionalized laponite (LaSH). The employed organolaponite was prepared by surface grafting of 3-mercaptopropyltrimethoxysilane (MPTMS), then characterized by XRD, FTIR spectroscopy, thermal analysis and CHS elemental analysis. The electrochemical behavior of CFX was investigated on the thin film GCE/LaSH by cyclic voltammetry, which showed a single irreversible oxidation peak at 1.3 V (vs. Ag/AgCl) in a Britton-Robinson buffer solution at pH 2. The CFX current response on the organoclay modified electrode was significantly improved, due to favorable interactions between thiol functional groups and CFX. Differential pulse stripping voltammetry was then applied for quantitative determinations, and key parameters such as pH of detection medium, accumulation time, agitation and CFX concentration were optimized. In optimum experimental conditions, a linear relationship between the peak current density and CFX concentration was observed in the range 10.0–110.0 µM, with a detection limit of 2.69 × 10–7 M (S/N = 3). Kinetic and chronocoulometric studies were also performed to characterize the diffusion of CFX at the modified organoclay electrode. The effect of some important potential interfering compounds on the stripping signal of CFX was also examined, followed by the application of the developed sensor in the determination of CFX in a pharmaceutical formulation using the standard addition method. Laponite clay mineral functionalised with thiol groups from MPTMS, exhibited more affinity towards Ciprofloxacin antibiotic, allowing its voltammetric detection in a commercial pharmaceutical sample

Highly Selective Voltammetric Sensor for l-Tryptophan Using Composite-Modified Electrode Composed of CuSn(OH)6 Microsphere Decorated on Reduced Graphene Oxide

In this study, a nanostructured CuSn(OH)6 microsphere decorated on reduced graphene oxide (CSOH/rGO) was prepared by a co-precipitation method followed by ultrasonication, which was used for the se...

Molecularly imprinted polymer nano-sphere/multi-walled carbon nanotube coated glassy carbon electrode as an ultra-sensitive voltammetric sensor for picomolar level determination of RDX

An ultrasensitive and highly selective voltammetric sensor with ultra-trace level detection limit is introduced for RDX determination in water samples. The sensing platform is the nano-sized molecularly imprinted polymer (nano-MIP)/MWCNTs nanocomposite, casted on glassy carbon electrode (GCE). The MIP was synthesized by copolymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of RDX via precipitation polymerization. The MIP was characterized by scanning electron microscopy (SEM) and fast fourier transform infrared spectroscopy (FT-IR). It was demonstrated that the MIP, coated on the electrode, have the capability to adsorb RDX and increase its related voltammetric signal. This capability was remarkably lower, for the non-imprinted polymer (NIP)-based electrode. The MIP-based electrode signal to RDX is greatly enhanced in the presence of MWCNTs. The sensor showed excellent selectivity to RDX, compared to similar compounds of HMX and TNT. It exhibited two dynamic linear ranges including 0.1–10.0 nmol L−1 and 0.01–1.00 µmol L−1. The detection limit and relative standard deviation of the sensor were calculated to be 20 pmol L−1(3Sb/m, first curve) and 4.5% (10 nmol L−1, n = 5), respectively. The utility of the sensor was checked for RDX analysis in water samples which led to satisfactory results.

Highly Selective Voltammetric Sensor Based on Molecularly Imprinted Polymer and Carbon Nanotubes to Determine the Dicloran Pesticide in Biological and Environmental Samples

Despite of increasing the food production by application of pesticides, the wide use of them can lead to environmental pollution and their residues in food. Due to the increasing application of pesticides, reliable and accurate analytical methods are necessary to analyze different occupational and environmental samples like air, water, soil, as well as also food containing these compounds. There are some traditional techniques to determine the pesticides such as liquid chromatography and gas chromatography with electron capture detection. The mentioned techniques are very expensive and a well-equipped laboratory and well-trained analysis operators are required. A sample pre-treatment step is needed to determine the analytes at ppb levels. Therefore, in the last few years many sensitive, selective, and accurate methods have been developed to determine the trace toxic species like pesticides. Electrochemical sensors are the appropriate and interested devices to monitor the trace and even ultra-trace pesticides. Molecular imprinted polymers (MIPs) can be used as recognition elements or modifying agents in sensors structure to increase their selectivity and improve their response. Recently, modified electrode by different modifying agents like MIPs and various nano structures are being used for quantification of analytes because of their interesting advantages. Modified electrodes may be used in combination with different electrochemical techniques. The aim of this study was to synthesize a molecularly imprinted polymer for dicloran for first time and then to apply it as a recognition element in the nano-composite carbon paste electrode for selective and sensitive electrochemical determining the dicloran pesticide in environmental and biological samples. Multi-walls carbon nanotubes (MWCNTs) and a molecularly imprinted polymer (MIP) were used as the modifiers in senor composition. A dicloran selective MIP and a non-imprinted polymer (NIP) were synthesized and applied in the carbon paste electrode. To prepare the bare carbon paste electrode (CP), graphite, MWCNT and paraffin oil were mixed. The MIP-CP and NIP-CP were prepared by mixing different percentages of graphite, MWCNT, paraffin oil, and MIP or NIP. This mixture was homogenized and final paste was packed into the end of an electrode body. After the optimization of electrode composition, it was used to extract the analyte in the sample and then was inserted in the electrochemical cell to determine the concentration of extracted analyte. Some parameters affecting the sensor response were optimized in the extraction and analysis steps, such as sample pH, electrolyte concentration and pH, stirring rate of analyte solution, as well as the instrumental parameters of square wave voltammetry (square wave amplitude and frequency, deposition potential and its exertion time, and electrolyte concentration). The MIP-CP electrode showed very high recognition ability in comparison to NIP-CP. The CP containing 22% MIP and 3% MWCNTs had the highest efficiency to adsorb the analyte and it was selected for later experiments. The electrode with MIP was very selective for dicloran, so that, other pesticides indicated no significant impact on its responses. Findings demonstrated the ability of MIP-CP electrode to interact strongly with the target compound due to specific cavities for molecules of interest in the MIP structure. The optimum conditions to extract the analyte on the electrode surface included the extraction pH of 6, the solution stirring rate of 700 rpm, and the extraction time of 20 min. In addition, the optimum analysis conditions were obtained as follow: the square wave amplitude 0.15 V, frequency 150 Hz, deposition potential of -0.5 V, its exertion time of 15s, analysis pH of 8, and electrolyte (KCl) concentration of 0.04 mol L-1. After optimization of all effective parameters on electrochemical determination of dicloran, the difference between responses of prepared MIP and NIP was studied. There was significant difference (P< 0.05) between these polymers to adsorb dicloran molecules, proving the formation of selective adsorption sites in the MIP structure. Figure 1 indicates the square wave voltammograms related to determination of defined concentration of dicloran by MIP-CP, NIP-CP, and bare CP. Finally in method validation, the obtained linear range in calibration curve was 1×10-6 to 1×10-9 molL-1 (R2: 0.987), The limit of detection (LOD) and limit of quantification (LOQ) were 4.8×10-10 and 9.4×10-10 mol L-1, respectively. In this work, a high selective square wave voltammetric sensor for the rapid detection of trace amounts of dicloran in environmental and biological samples has been designed and applied. The modification of electrode can considerably enhance the selective response of electrode to determine the analyte of interest. The designed sensor was successfully used for determination of dicloran in different real samples (tap water, river water, and urine) with no special sample preparation procedure. The ability of MIP-CP electrode to interact strongly with the target compound due to specific cavities lead to high selectivity.

Voltammetric sensor for tartrazine determination in soft drinks using poly (p-aminobenzenesulfonic acid)/zinc oxide nanoparticles in carbon paste electrode

Zinc oxide nanoparticles (ZnO NPs) and p-aminobenzenesulfonic acid (p-ABSA) were used to fabricate a modified electrode, as a highly sensitive and selective voltammetric sensor, for the determination of tartrazine. A fast and easy method for the fabrication of poly p-ABSA (Pp-ABSA)/ZnO NPs-carbon paste electrode (Pp-ABSA/ZnO NPs-CPE) by cyclic voltammetry was used. By combining the benefits of Pp-ABSA, ZnO NPs, and CPE, the resulted modified electrode exhibited outstanding electrocatalytic activity in terms of tartrazine oxidation by giving much higher peak currents than those obtained for the unmodified CPE and also other constructed electrodes. The effects of various experimental parameters on the voltammetric response of tartrazine were investigated. At the optimum conditions, the sensor has a linear response in the concentration range of 0349–5.44 μM, a good detection sensitivity (2.2034 μA/μM), and a detection limit of 80 nM of tartrazine. The proposed electrode was used for the determination of tartrazine in soft drinks with satisfactory results.

Preparation of Pb(II) Ion Imprinted Polymer and Its Application as the Interface of an Electrochemical Sensor for Trace Lead Determination.

An ion imprinted polymer (IIP) was synthesized by using Pb(II) as a template, methacrylic acid as a monomer, 8-hydoxyquinoline as a ligand, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, and azobisisobutyronitrile as initiator. It can be applied to prepare lead ion selective voltammetric sensor for Pb(II) adsorption and trace detection. The Pb(II)-IIP was characterized by FTIR spectra and SEM image. Under optimized conditions of polymerization, the Pb(II)-IIP showed good adsorption behavior toward Pb(II), with a magnitude of three times higher than that of the non imprinted polymer (NIP). Also, it exhibited a favorable selectivity for Pb(II), compared with other heavy metal ions of Hg(II), Cd(II), Cu(II), and a negligible adsorption to the other cations. The synthesized IIP was used to determine trace levels of Pb(II) in food and water samples, with a calibration linear range over Pb(II) concentrations of 0.05 - 60 μM and a limit of detection at 0.01 μM.

Selective voltammetric sensor for nanomolar detection of silver ions using carbon paste electrode modified with novel nanosized Ag(I)-imprinted polymer

In this paper, a novel nanosized silver imprinted polymer was successfully synthesized for the stripping voltammetric detection of silver ions. The Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and thermogravimetric analysis (TGA) were used to characterize the as-prepared ion-imprinted polymer (IIP). The electrochemical procedure was based on the accumulation of silver ions at the surface of a modified carbon paste electrode (MCPE) with nanosized silver IIP and multi-walled carbon nanotubes (MWCNTs). After optimization, the resulting electrode exhibited a linear relationship toward Ag(I) concentrations ranging from 0.5×10−9 to 2.8×10−7M. The limit of detection (LOD) was found to be 1.2×10−10M (S/N=3). The relative standard deviation (RSD) for 9 successive measurements at different electrodes was found to be 2.8% (conc.: 50.0nM). The interference studies showed that the several common metal ions did not interfere with the quantitative silver determination. Finally, because of high selectivity and sensitivity of the proposed modified electrode, it was applied for determination of silver in the environmental water samples and the certified reference material.

Cefixime detection by a novel electrochemical sensor based on glassy carbon electrode modified with surface imprinted polymer/multiwall carbon nanotubes

A new selective voltammetric sensor based on molecularly imprinted polymer immobilized on multiwall carbon nanotube surface was reported for determination of cefixime in this paper. For this, cefixime was first assembled on the surface of carboxyl-functionalized multiwall carbon nanotube modified glassy carbon electrode by the formation of covalent bonds. Then molecular imprinting polymers were formed with incubating the prepared electrode in mixture solution of acrylamide as functional monomer and N,N methylenebisacrylamide as cross linker. Ag dendrites were electrodeposited on the surface of molecular imprinting polymers and were used to increase the electrode surface area and to amplify the sensor signal. The morphology of the fabricated electrode was investigated by cyclic voltammetry, scanning electron microscopy, and electrochemical impedance spectroscopy techniques. Under the optimal experimental condition, the voltammetry responses were linearly related to cefixime concentration between 0.01 and 600.0μM and a limit of detection of 0.001μM was achieved. Finally, the proposed sensor was successfully applied to determination of cefixime in pharmaceutical formulations and urine samples.