Differential Pulse Voltammetric Analysis Research Articles

Preparation and Characterization of Patuletin-Loaded Chitosan Nanoparticles with Improved Selectivity and Safety Profiles for Anticancer Applications

Objective. This study aimed to investigate the preparation of patuletin-encapsulated chitosan nanoparticles (PT-CS-NPs) using the ionic gelation method, evaluate their potential as anticancer agents, and invent a new method of differential pulse voltammetric analysis for patuletin (PT). Methods. Computational studies were conducted to assess the affinity of PT for chitosan, confirming a promising interaction. PT-CS-NPs were synthesized based on the computational outputs, resulting in nanoparticles with an angular structure and an average size of 6.168 nm. The cytotoxicity of PT and PT-CS-NP was evaluated in breast and colon cancer cell lines, and selectivity indices were calculated to assess safety profiles. The electrochemical behavior of PT was also investigated using the Britton–Robinson buffer. Results. PT-CS-NP exhibited both potent cytotoxicity and a favorable safety profile, showing the most active and safest pattern of cytotoxicity among the tested compounds. The electrochemical oxidation of PT was observed at 0.531 V vs. Ag/AgCl at pH 4.0.0. The concentration of PT showed a linear relationship with the corresponding peak current over the range of 10.0 x 10 − 9 : 10.0 x 10 − 5 M M, with a minimum limit of detection of 3.4 × 10(−9)M. The proposed method successfully measured PT, with a relative standard deviation below 2%. Conclusion. The preparation of PT-CS-NP via the ionic gelation method resulted in angular nanoparticles with a promising anticancer activity and safety profiles. The electrochemical behavior of PT was characterized, and a reliable method for PT quantification was established.

Probing the Use of Homemade Carbon Fiber Microsensor for Quantifying Caffeine in Soft Beverages.

In the development of electrochemical sensors, carbon micro-structured or micro-materials have been widely used as supports/modifiers to improve the performance of bare electrodes. In the case of carbon fibers (CFs), these carbonaceous materials have received extensive attention and their use has been proposed in a variety of fields. However, to the best of our knowledge, no attempts for electroanalytical determination of caffeine with CF microelectrode (µE) have been reported in the literature. Therefore, a homemade CF-µE was fabricated, characterized, and used to determine caffeine in soft beverage samples. From the electrochemical characterization of the CF-µE in K3Fe(CN)6 10 mmol L-1 plus KCl 100 mmol L-1, a radius of about 6 µm was estimated, registering a sigmoidal voltammetric profile that distinguishes a µE indicating that the mass-transport conditions were improved. Voltammetric analysis of the electrochemical response of caffeine at the CF-µE clearly showed that no effects were attained due to the mass transport in solution. Differential pulse voltammetric analysis using the CF-µE was able to determine the detection sensitivity, concentration range (0.3 to 4.5 µmol L-1), limit of detection (0.13 μmol L-1) and linear relationship (I (µA) = (11.6 ± 0.09) × 10-3 [caffeine, μmol L-1] - (0.37 ± 0.24) × 10-3), aiming at the quantification applicability in concentration quality-control for the beverages industry. When the homemade CF-µE was used to quantify the caffeine concentration in the soft beverage samples, the values obtained were satisfactory in comparison with the concentrations reported in the literature. Additionally, the concentrations were analytically determined by high-performance liquid chromatography (HPLC). These results show that these electrodes may be an alternative to the development of new and portable reliable analytical tools at low cost with high efficiency.

Differential Pulse Voltammetric Analysis of Hydrazine in Water Samples by Using Screen-Printed Graphite Electrode Modified with Nitrogen-Doped Hollow Carbon Spheres

The present study introduces a facile and efficient voltammetric hydrazine sensor via the modification of screen-printed graphite electrode (SPGE) with nitrogen-doped hollow carbon spheres (N-HCSs). This work is the first report of the new method of electroanalytical determination of hydrazine through N-HCSs modified SPGE. The N-HCSs fabricated through the templating approach (hard template) were characterized by Fourier transform infrared (FT-IR) spectroscopy, field emission-scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry (CV), chronoamperometry (CA), and differential pulse voltammetry (DPV) were employed for electrochemical determinations. The produced N-HCSs/SPGE had an appreciable electrocatalytic capacity for the hydrazine oxidation, with the least oxidation overpotential and elevated voltammetric peak currents. The peak current of hydrazine oxidation on N-HCSs/SPGE possessed a distinct linear association with its levels (0.02–380.0 μM) under the optimized experimental circumstances, with the limit of detection (LOD) as narrow as 0.007 μM. Good stability and acceptable reproducibility were also attained on the N-HCSs/SPGE. In addition, the developed technique exhibited good selectivity toward the detection of hydrazine in the presence of some interfering species. The practical applicability of proposed sensor was successful by sensing hydrazine in water samples.

Simultaneous electrochemical determination of hydrazine and hydroxylamine on a thiadiazole derivative modified pencil graphite electrode

This work explores the fabrication of an electrochemical sensor for the simultaneous determination of hydrazine (HY) and hydroxylamine (HA) using a modified pencil graphite electrode (PGE). The PGE was modified by the electropolymerization of 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) in an acidic medium. The modified electrode was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), IR spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The developed sensor showed a linear range of 1.5 mM–167.42 mM and 0.5–167.42 mM for HY and HA respectively in 0.1 M KCl medium, which is higher than the reported literature for both analytes. The sensing device showed lower detection limits of 0.08 mM and 0.82 mM for HA and HY, respectively. The electrochemical oxidation of HA and HY on the modified electrode was found to be an irreversible diffusion-controlled reaction. The electroactive surface area and electron transfer rate constant of the modified electrode were also calculated. The bare PGE does not separate the voltammetric signals of HA and HY. However, the modified PGE was successful in resolving the oxidation peaks of HA and HY at 0.73V and 0.29 V. The electrochemical determination of both analytes was done by differential pulse voltammetric analysis (DPV). The sensor showed only negligible interference with some of the co-existing species of the analytes in the real sample. The repeatability, reproducibility and stability of the electrode were satisfactory with good recovery of the analytes from tap water and river water samples.

Hybrid Nanostructure Composed of Homogeneously Decorated MoS2 Nanosheets on Graphene for Simultaneous Electrochemical Determination of Amlodipine and Hydrochlorothiazide

A single-stage hydrothermal approach was performed for the synthesis of molybdenum disulfide nanosheets/graphene (MoS2 NSs-G) hybrid nanostructures, in which the surface of graphene is tightly and homogeneously decorated with MoS2 nanosheets. XRD, TEM, FE-SEM, and EDX analysis were performed to confirm the structural characteristics of MoS2 NSs-G. The MoS2 NSs-G hybrid modified screen-printed carbon electrode (MoS2 NSs-G/SPCE) was fabricated by drop-casting the hybrid suspension on the surface of an SPCE. The assessment of the electrochemical behavior of amlodipine at the surface of MoS2 NSs-G/SPCE was carried out by cyclic voltammetry (CV) and differential pulse voltammetric analysis (DPV). The modified electrode exhibited superior electrocatalytic activity for the oxidation of amlodipine compared to the bare SPCE. The structure of MoS2 NSs with plenty of edge sites and synergistic effects between MoS2 NSs and graphene can promote electrochemical performances. The MoS2 NSs-G/SPCE provides satisfactory results, reaching a limit of detection (LOD) of 0.0012 μM for the determination of amlodipine within a linear range of 0.04–400.0 μM. Moreover, the sensor shows favorable results for the concurrent measurement of amlodipine and hydrochlorothiazide. The key advantages of the fabricated sensor include stability and enhanced sensitivity, which will be favorable for amlodipine and hydrochlorothiazide clinical assay.

Solid-state synthesis of Ag-doped PANI nanocomposites for their end-use as an electrochemical sensor for hydrogen peroxide and dopamine

Polyaniline protected silver nanoparticles (Ag-doped PANI nanocomposites) were synthesized successfully by a solid-state mechano-chemical oxidative polymerization. AgNO3 acted as a metal precursor as well as an oxidizing agent. The prepared Ag-doped PANI nanocomposites were characterized by various techniques such as TEM, FE-SEM, XRD, FTIR and UV–vis spectroscopy. XRD confirmed the cubic FCC form of the Ag nanoparticles with an average crystal size of ~36.04 nm for the Ag-doped PANI nanocomposites. FE-SEM and TEM analysis of Ag-doped PANI nanocomposites revealed the formation of spherical as well as semi-spherical Ag nanoparticles embedded in the PANI polymer matrix. Cyclic voltammogram revealed excellent electrochemical responses and electrocatalytic behavior of the Ag-doped PANI nanocomposites/GCE for hydrogen peroxide (H2O2) and dopamine (DA). Based on cyclic, amperometric and differential pulse voltammetric analysis, it was found that H2O2 undergoes reduction whereas DA is oxidized at the surface of the modified Ag-doped PANI nanocomposites/GCE. For H2O2 and DA, the detection limits as measured from differential pulse voltammetric analysis were 0.03 µM and 0.12 µM, respectively.

Indirect differential pulse voltammetric analysis of cyanide at porous copper based metal organic framework modified carbon paste electrode: Application to different water samples

Carbon paste electrode (CPE) modified with porous copper based metal organic framework (Cu-MOF) nanocomposite is described for analysis of cyanide (CN−) for the first time. The electrochemical performance of the proposed electrode was investigated by differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The Cu-MOF nanocomposite was characterized using scanning electron microscope (SEM), N2-adsorption-desorption isotherms, powder X-ray powder diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Under optimal conditions of measurements, the anodic peak (Ipa) decreases linearly in the range of 1.87–25 μM with LOD of 0.60 μM (at S/N = 3). The Cu-MOF/CPE showed good selectivity towards CN− measurement with no significant interference in pH 7.0 using 0.25 M KCl to increase the medium conductivity and to stabilize the analyte and prevents its volatility. Moreover, the method was successfully applied for determination of CN− in different environmental water samples.

Three-Electrode 30–60 μL Mini-Cell for Ecologically Conscious Analytical Voltammetry with Common Macro- and Microelectrodes

A 30–60 μL three-electrode electrochemical mini-cell for analytical voltammetry is described. The main module is a platinum tube (Pt-T) of 4 mm diameter and 5 mm height, which, when vertically placed on an upright working electrode, serves both as a counter electrode and electrolyte container. A fritted mini Ag/AgCl reference electrode completes the electrochemical cell by contacting the electrolyte through the top of the Pt tube. The Pt-T mini-cell produced typical cyclic voltammograms for 30 μL hexacyanoferrate(III) with all types of working electrode tested, i.e., Pt, Au, boron-doped diamond and glassy carbon disc macroelectrodes, a cylindrical pencil lead electrode, and Pt disc microelectrodes. The mini-cell was also shown to be suitable for drug, hormone, antioxidant, and redox-label voltammetry, for operation of a glucose biosensor, and for quantitative differential pulse voltammetric analysis of paracetamol in standard addition mode. The significant technical advantages of the mini-cell are its cheapness and simplicity of construction, indefinite reusability, wide analyte adaptability, and ability to incorporate practically all standard macro- and microelectrode designs. Consequently, the mini-cell is not only a valuable option for voltammetric work in general, but more importantly it facilitates, in a simple and inexpensive manner, electrochemical analysis of samples with a mass or volume constraint or when the chemicals involved are costly. The microliters-volume electrochemical cell described in this study helps waste reduction and reduces chemical usage and, compared with conventional milliliters-volume beaker-type cells, is thus a green and sustainable electroanalytical tool that supports eco-friendly practice in research, commercial, and teaching laboratories.

Lanthanum doped fern-like CuO nanoleaves/MWCNTs modified glassy carbon electrode for simultaneous determination of tramadol and acetaminophen

An innovative and adept single-stage approach was created to synthesis lanthanum doped fern like CuO nanoleaves (La3+-CuO fern-like nanoleaves). The morphology and structure of fern like La3+-CuO nanoleaves are characterized by using the FT-IR, EDX, SEM, XPS and TEM techniques. Drop casting fern-like La3+-CuO nanoleaves suspension on MWCNTs/GC was used to fabricate the La3+-CuO/MWCNTs nanocomposites modified glassy carbon (GC) electrode. For electrochemical behavioral assessment of tramadol, differential pulse voltammetric analysis (DPV) and cyclic voltammetry (CV) was implemented and the oxidation performance on MWCNTs/GC, La3+-CuO/MWCNTs/GC and bare GC was compared. The obtained results indicate that amalgamation of fern-like La3+-CuO nanoleaves and multiwall carbon nanotubes will entail a significant improvement of sensor sensitivity. A limit detection of 0.014 μM within a linear range of 0.5–900.0 μM was determined for obtaining the quantitative tramadol detection. Moreover, this sensor proved favorable to simultaneously determine tramadol and acetaminophen. Additionally, great sensitivity and stability was shown by the fabricated sensor which will be beneficial for tramadol and acetaminophen clinical assay.

Layer-by-Layer-Assembled AuNPs-Decorated First-Generation Poly(amidoamine) Dendrimer with Reduced Graphene Oxide Core as Highly Sensitive Biosensing Platform with Controllable 3D Nanoarchitecture for Rapid Voltammetric Analysis of Ultratrace DNA Hybridization.

The structure and electrochemical properties of layer-by-layer-assembled gold nanoparticles (AuNPs)-decorated first-generation (G1) poly(amidoamine) dendrimer (PD) with reduced graphene oxide (rGO) core as a highly sensitive and label-free biosensing platform with a controllable three-dimensional (3D) nanoarchitecture for the rapid voltammetric analysis of DNA hybridization at ultratrace levels were characterized. Mercaptopropinoic acid (MPA) was self-assembled onto Au substrate, then GG1PD formed by the covalent functionalization between the amino terminals of G1PD and carboxyl terminals of rGO was covalently linked onto MPA, and finally AuNPs were decorated onto GG1PD by strong physicochemical interaction between AuNPs and -OH of rGO in GG1PD, which was characterized through different techniques and confirmed by computational calculation. This 3D controllable thin-film electrode was optimized and evaluated using [Fe(CN)6]3-/4- as the redox probe and employed to covalently immobilize thiol-functionalized single-stranded DNA as biorecognition element to form the DNA nanobiosensor, which achieved fast, ultrasensitive, and high-selective differential pulse voltammetric analysis of DNA hybridization in a linear range from 1 × 10-6 to 1 × 10-13 g m-1 with a low detection limit of 9.07 × 10-14 g m-1. This work will open a new pathway for the controllable 3D nanoarchitecture of the layer-by-layer-assembled metal nanoparticles-functionalized lower-generation PD with two-dimensional layered nanomaterials as cores that can be employed as ultrasensitive and label-free nanobiodevices for the fast diagnosis of specific genome diseases in the field of biomedicine.

Microfluidic platform integrated with graphene-gold nano-composite aptasensor for one-step detection of norovirus

Noroviruses are a foremost cause of gastroenteritis outbreaks throughout the world. On-site sample processing and detection of the viral clinical samples has always been a problem. This study reports an all-polydimethylsiloxane microfluidic chip integrated with screen-printed carbon electrode for the electrochemical detection of norovirus. The microfluidic chip contained packed silica microbeads zones to filter and enrich the norovirus infected clinical sample. Selective detection of norovirus was accomplished by functionalizing the graphene-gold nanoparticles composite modified carbon electrode with the viral capsid-specific aptamer. Norovirus specific aptamer was tagged with a ferrocene molecule, which acts a redox probe. The interaction of aptamer and norovirus resulted in a decrease in the electrochemical signal from ferrocene. The microfluidic chip and functionalized electrodes were characterized using several microscopic and electrochemical techniques. The optimized microfluidic aptasensor was employed to detect a range of norovirus concentration. Using differential pulse voltammetric analysis, a detection limit of 100 pM with a detection range from 100 pM to 3.5nM for norovirus was obtained. The application of aptasensor was also assessed by detecting norovirus in spiked blood samples. The aptasensor could easily discriminate between the target norovirus and other interfering molecules. The developed microfluidic aptasensor has the potential to be used for point-of-care one-step detection of norovirus in clinical samples.

A sensitive amplified sensor based on improved carbon paste electrode with 1-methyl-3-octylimidazolium tetrafluoroborate and ZnO/CNTs nanocomposite for differential pulse voltammetric analysis of raloxifene

In this work, we suggested a carbon paste electrode improved with 1-methyl-3-octylimidazolium tetrafluoroborate (1-M-3-OITFB) and ZnO/CNTs nanocomposite (1-M-3-OITFB/ZnO/CNTs/CPE) for electrochemical determination of raloxifene (RXF) as a non-steroidal selective estrogen receptor regulator. The cyclic and differential pulse voltammetric methods were apply for investigation of RXF electrochemical response at a surface of 1-M-3-OITFB/ZnO/CNTs/CPE. Under the best experimental conditions, the 1-M-3-OITFB/ZnO/CNTs/CPE showed a wide linear dynamic range of 0.08 − 400.0μM. We detected a detection limit of 0.04μM for RXF analysis using differential pulse voltammetric method (DPV). The 1-M-3-OITFB/ZnO/CNTs/CPE showed high performance ability to RXF analysis in trace amounts on pharmaceutical and clinical preparations.

Simultaneous differential pulse voltammetric analysis of guanine and adenine using graphitized carbon nanofibers modified electrode

Simultaneous differential pulse voltammetric analysis of guanine and adenine using graphitized carbon nanofibers modified electrode

Electroanalytical determination of metronidazole in tablet dosage form

In this study, the electrochemical reduction and determination of met- ronidazole were easily realized in Britton-Robinson buffer (pH 4.01) using an UTGE by cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. In this acidic medium, one irreversible and a sharp cathodic peak were observed. A linear calibration curve for DPV analysis was constructed in the metronidazole concentration range 3×10 -6 -9×10 -5 mol L -1 . The limit of de- tection (LOD) and limit of quantification (LOQ) were 1.42×10 -7 and 4.76×10 -7 mol L -1 respectively.

Enhancement of the electrochemical behavior of CuO nanoleaves on MWCNTs/GC composite film modified electrode for determination of norfloxacin

A novel and facile (single-step) method was developed for the synthesis of CuO nanoleaves in the presence of a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA) at pH 10.5. The mechanism and self-assembly for the formation of CuO nanoleaves are discussed. The structure and morphology of CuO nanoleaves are characterized by means of Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopic (TEM) studies. The CuO/MWCNTs modified glassy carbon (GC) electrode was fabricated via the drop-casting of CuO nanoleaves suspension on MWCNTs/GC surface. In order to investigate the electrochemical behavior of norfloxacin, cyclic voltammetry (CV) and differential pulse voltammetric analysis (DPV) were carried out and compare the oxidation behavior on CuO/MWCNTs/GC, MWCNTs/GC and bare GC. The electrocatalytic oxidation of norfloxacin was studied (pH 7.2) on CuO/MWCNTs/GC electrode and found an irreversible behavior in the range from 0 to +1.1V with an oxidation peak at 0.91V in physiological conditions. The quantitative detection of norfloxacin was obtained with a limit of detection of 3.21×10−7M within a linear range from 1μM to 47.7μM.

Differential pulse voltammetric analysis of lead in vegetables using a surface amino-functionalized exfoliated graphite nanoplatelet chemically modified electrode

A surface amino-functionalized (CONH2) exfoliated graphite nanoplatelet (xGnP) bismuth-modified electrode (CONH2xGnP/glassy carbon electrode GCE) for the determination of lead was developed and characterized. The hybrid material was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The electrochemical properties of the CONH2xGnP bismuth-modified electrode were characterized by a physical deposition method, depositing the film on a graphite electrode. The differential pulse response was linear over the Pb(II) concentration range of 0.005–0.045μgL−1, with a limit of detection of 0.001μgL−1, and the linear regression equation was y=3.75x+0.73. In vegetable juice (cabbage), the current increased linearly relative to the Pb(II) concentrations over the concentration range 0.005–0.035μgL−1 with the corresponding linear regression equations: y=13.06x+0.46, R2=0.9970.

Application of graphene for preconcentration and highly sensitive stripping voltammetric analysis of organophosphate pesticide

Electrochemical reduced β-cyclodextrin dispersed graphene (β-CD-graphene) was developed as a sorbent for the preconcentration and electrochemical sensing of methyl parathion (MP), a representative nitroaromatic organophosphate pesticide with good redox activity. Benefited from the ultra-large surface area, large delocalized π-electron system and the superconductivity of β-CD-graphene, large amount of MP could be extracted on β-CD-graphene modified electrode via strong π–π interaction and exhibited fast accumulation and electron transfer rate. Combined with differential pulse voltammetric analysis, the sensor shows ultra-high sensitivity, good selectivity and fast response. The limit of detection of 0.05 ppb is more than 10 times lower than those obtained from other sorbent based sensors. The method may open up a new possibility for the widespread use of electrochemical sensors for monitoring of ultra-trace OPs.

Determination of Trace Metals by Differential Pulse Voltammetry at Chitosan Modified Electrodes

Surface modification by chitosan (CT) on a glassy carbon electrode (GCE) was employed in the present study to determine metal traces (Cu, Pb, Cd, Co, As and Pt). Previous report about the chitosan film affinity toward positive or negative species demonstrated and allowed the application of these polymeric films for detecting heavy metals in aqueous solutions. The modified surface exhibited an affinity to chelating metal ions in solution, forming complexes. Differential pulse voltammetry combined with a pre-concentrating process and standard addition method were employed for trace analysis, obtaining the detection ranges (Cu (II) from 3.99×10 -6 to 3.91×10 -5 mol L -1 , Pb(II) from 1.99×10 -6 to 1.58×10 -5 mol L -1 , Cd(II) from 1.59×10 -5 to 6.23×10 -5 mol L -1 , As(IV) from 7.99×10 -6 to 5.04×10 -5 mol L -1 , Pt(IV) from 8.19×10 -6 to 3.59×10 -5 mol L -1 , Co(II) from 6.11×10 -4 to 2.78×10 -3 mol L -1 ), calibrations plots and relevant equations for each metal. Finally, cyclic voltammetry technique was used to characterize the polymeric surface behavior in presence of different metals and during the differential pulse voltammetric analysis. The results are described and discussed in the light of the existing literature.

Synthesis and Electrochemistry of Double-Decker Buckyferrocenes

D5d- and C5v-symmetric double-decker buckyferrocene Fe2(C60R10)Cp2 (R10 = Me5Ph5 and Me10) represents a new type of diiron complexes featuring conjugative connection of two ferrocene groups by a hoop-shaped [10]cyclophenacene. The compounds exhibit two-electron oxidation and two-electron reduction behavior, generating dicationic and dianionic species. The two iron atoms interact with each other through the pi-conjugation of the cyclophenacene, as revealed by differential pulse voltammetric analysis of the D5d Fe2(C60Me10)Cp2.

Ferrocenyl naphthalene diimide can bind to DNA·RNA hetero duplex: potential use in an electrochemical detection of mRNA expression

The novel ferrocenyl naphthalene diimide derivative 1 was synthesized by the condensation reaction between ferroceneacetic acid and terminal amino moieties of two imide substituents of naphthalene diimide. Stopped-flow analysis of the ligand 1 and DNA interaction revealed the following results: (i) the ligand binds to double stranded DNA more strongly than to single stranded DNA; (ii) the ligand does not have a bias against DNA sequence; (iii) the ligand can bind to the DNA·RNA hetero duplex more strongly than to the DNA·DNA duplex. These properties of 1 make it a suitable ligand for analysis of not only DNA but RNA. In fact, a current due to 1 was observed at 269 mV in the differential pulse voltammetric analysis of dA 20-immobilized electrode in an electrolyte containing 1. The current increased markedly upon hybridization with polyU, whereas no current increase was obtained for polyA. Since the DNA·RNA hetero duplex is formed between sample RNA and DNA on the electrode, 1 may be used for the electrochemical detection of mRNA expression.