Renewable Pencil Electrodes for Highly Sensitive Anodic Stripping Voltammetric Determination of 3‐Hydroxyflavone and Morin in Bulk Form and in Biological Fluids

An electrochemical anodic adsorptive stripping procedure for ultra‐trace assay of 3‐hydroxyflavone (3HF) and Morin at a renewable pencil electrode (PGE) in bulk form and in biological fluids is described. The nature of the oxidation process of 3HF and Morin taking place at the PGE was characterized by cyclic voltammetry. The results show that the determination of the oxidation peak current is the basis of a simple, accurate and rapid method for quantification of 3HF by square‐wave anodic stripping voltammetry. Determination of Morin was achieved by square‐wave anodic adsorptive stripping voltammetry of the formed Morin? Cu(II) complex at a PGE. Factors influencing the trace measurements of 3HF and the Morin? Cu (II) complex at a PGE are assessed. The limits of detection and quantitation for the determination of 3HF and Morin in bulk form and in biological fluids were determined. The statistical analysis and the calibration curve data for trace determination of 3HF and Morin are reported.     

Determination of trace metoclopramide by anodic stripping voltammetry with nafion modified glassy carbon electrode

A novel method is described for determination of metoclopramide (MCP) by second-derivative adsorptive anodic stripping voltammetry with a nafion-modified electrode. The stripping peak current is proportional to the concentration of MCP over the range 1.2×10⁻⁹–4.6×10⁻⁷ M. The detection limit is 8.0×10⁻¹¹ M with 4-min accumulation. The method has been successfully applied to the determination of MCP in human serum.     

Simultaneous Determination of Tyrosine and Histidine by Differential Pulse Cathodic Stripping Voltammetry Using H‐point Standard Addition Method in Tap and Seawater

H‐point standard addition method (HPSAM) has been applied for simultaneous determination of tyrosine and histidine in trace levels using copper ions by adsorptive cathodic stripping voltammetry. The amino acids‐Cu(II) complexes were accumulated onto the surface of a hanging mercury drop electrode for 40 s. The reduction peaks of preconcentrated complexes were used for simultaneous determination of amino acids in the range 8.0–180 and 30–1100 nM for tyrosine and histidine respectively. The effect of various parameters such as pH, concentration of copper, accumulation time and scan rate on the selectivity were studied. Under the optimized conditions the method was successfully applied for determination of tyrosine and histidine in synthetic and real samples.     

Determination of Sb(V) Using Differential Pulse Anodic Stripping Voltammetry at an Unmodified Edge Plane Pyrolytic Graphite Electrode

Antimony(V) determination at an unmodified edge plane pyrolytic graphite (EPPG) electrode using anodic stripping voltammetry (ASV) by depositing beyond the hydrogen wave is shown in this paper. By depositing beyond the hydrogen wave, we report a sensitive method to determine pentavalent antimony at a carbon electrode in 0.25 M HCl. Using differential pulse anodic stripping voltammetry (DPASV), a bare EPPG electrode gave a detection limit of 5.8±0.02 nM without the need for surface modification. This level is greatly within the EU limit for drinking water of 40 nM.     

Extraction of PCDD/PCDF from soil with supercritical CO2: Optimization by a three-level factorial design approach

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCl solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH₃/NH₄Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 × 10^–4 M). Finally, 1 × 10^–5 M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 × 10^–10 to 1.05 × 10^–9 M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.     

Square Wave Cathodic Adsorptive Stripping Voltammetric Determination of the Anticancer Drugs Flutamide and Irinotecan in Biological Fluids Using Renewable Pencil Graphite Electrodes

A sensitive electrochemical method based on square wave cathodic adsorptive stripping voltammetry (SWCASV) using pencil graphite electrodes (PGE) was developed for the individual and simultaneous determination of the anticancer drugs flutamide (Flu) and irinotecan (Irino) in biological fluids. Calibration curves showed an excellent linear response with limits of detection of 1.68×10^?9 and 1.55×10^?8 M Irino and Flu, respectively. The statistical evaluation of within‐day repeatability (n=5) and day to day precision (n=5) showed satisfactory accuracy and precision. SWCASV using a PGE for individual and simultaneous determination of both drugs in bulk form, human urine and serum samples was demonstrated.     

Stripping voltammetry study of ultra-trace toxic metal ions on highly selectively adsorptive porous magnesium oxide nanoflowers

We have demonstrated highly selective and sensitive detection of Pb(II) and Cd(II) using a highly selective adsorptive porous magnesium oxide (MgO) nanoflowers. The MgO nanoflower-modified glassy carbon electrode was electrochemically characterized using cyclic voltammetry; and the anodic stripping voltammetric performance of bound Pb(II) and Cd(II) was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The MgO nanoflower-modified electrode exhibited excellent sensing performance toward Pb(II) and Cd(II) that was never observed previously at bismuth (Bi)-based electrodes. Simultaneous additions of Pb(II) and Cd(II) were investigated in the linear range from 3.3 to 22 nM for Pb(II) and 40 to 140 nM for Cd(II), and detection limits of 2.1 pM and 81 pM were obtained, respectively. Some foreign ions, such as Cu(II), Zn(II) and Cr(III) do not interfere with the detection of Pb(II) and Cd(II). To the best of our knowledge, this is the first example of a highly adsorptive metal oxide with hierarchical micro/nanostructure that allows the detection of both Pb(II) and Cd(II) ions.     

A novel sensitive electrochemical DNA biosensor for assaying of anticancer drug leuprolide and its adsorptive stripping voltammetric determination

The anticancer drug, leuprolide (LPR) bound to double-stranded fish sperm DNA (dsDNA) which was immobilized onto the surface of an anodically activated pencil graphite electrode (PGE), was employed for designing a sensitive biosensor. The interaction of leuprolide (LPR) with double-stranded DNA (dsDNA) immobilized onto pencil graphite electrode (PGE) have been studied by electrochemical methods. The mechanism of the interaction was investigated and confirmed by differential pulse voltammetry using two different interaction methods; at the PGE surface and in the solution phase. The decrease in the guanine oxidation peak current was used as an indicator for the interaction in acetate buffer at pH 4.80. The response was optimized with respect to accumulation time, potential, drug concentration, and reproducibility for both interaction methods. The linear response was obtained in the range of 0.20-6.00 ppm LPR concentration with a detection limit of 0.06 ppm on DNA modified PGE and between 0.20 and 1.00 ppm concentration range with detection limit of 0.04 ppm for interaction in solution phase method. LPR showed an irreversible oxidation behavior at all investigated pH values on a bare PGE. Differential pulse adsorptive stripping (AdSDPV) voltammetric method was developed for the determination of LPR. Under these conditions, the current showed a linear dependence with concentration within a range of 0.005-0.20 ppm with a detection limit of 0.0014 ppm. Each determination method was fully validated and applied for the analysis of LPR in its pharmaceutical dosage form.     

Fullerene-based anodic stripping voltammetry for simultaneous determination of Hg(II), Cu(II), Pb(II) and Cd(II) in foodstuff

Various carbon nanomaterials for use in anodic stripping voltammetric analysis of Hg(II), Cu(II), Pb(II) and Cd(II) are screened. Graphene, carbon nanotubes, carbon nanofibers and fullerene (C₆₀), dispersed in chitosan (Chit) aqueous solution, are used to modify a glassy carbon electrode (GCE). The fullerene-chitosan modified GCE (C₆₀-Chit/GCE) displays superior performance in terms of simultaneous determination of the above ions. The electrodes and materials are characterized by electrochemical impedance spectroscopy, cyclic voltammetry, scanning electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The excellent performance of C₆₀-Chit/GCE is attributed to the good electrical conductivity, large surface area, strong adsorption affinity and unique crystalline structure of C₆₀. Using differential pulse anodic stripping voltammetry, the assay has the following features for Hg(II), Cu(II), Pb(II) and Cd(II), respectively: (a) Peak voltages of +0.14, ?0.11, ?0.58 and???0.82 V (vs SCE); (b) linear ranges extending from 0.01–6.0 μM, 0.05–6.0 μM, 0.005–6.0 μM and 0.5–9.0 μM; and (c), detection limits (3σ method) of 3 nM (0.6 ppb), 14 nM (0.9 ppb), 1 nM (0.2 ppb) and 21 nM (2.4 ppb). Moreover, the modified GCE is well reproducible and suitable for long-term usage. The method was successfully applied to the simultaneous determination of these ions in spiked foodstuff.

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Graphical abstract Compared with graphene, carbon nanotubes and carbon nanofibers, an electrode modified with fullerene in chitosan electrode displays superior performance for the simultaneous anodic stripping voltammetric detection of Hg(II), Cu(II), Pb(II) and Cd(II).

     

Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.     

The determination of nanomolar levels of nitrite in fresh and sea water by cathodic stripping voltammetry

Adsorptive cathodic stripping voltammetry (CSV) is used for the determination of nitrite in natural waters, including sea water. The nitrite is first derivatised by diazotization with sulphanilamide, followed by coupling to 1-naphthylamine to produce an azo dye. This azo dye adsorbs on the mercury drop electrode and its reduction is fully reversible. The concentration of the dye is linearly related to the height of the reduction peak for nitrite concentrations between 0.3 and 200 nM. The optimal concentrations of sulphanilamide and naphthylamine are 2 mM and 0.1 mM, respectively, at a pH of 2.5. After diazotization and coupling, the differential-pulse CSV of the azo dye is done at pH 8.4 with an adsorption potential of ?0.3 V. The standard deviation of a determination of 4 nM nitrite is ±2% and the limit of detection is 0.3 nM for an adsorption time of 60 s. The linear range can be extended by using shorter adsorption times. These sensitivity in sea water is the same as that in fresh water. The concentration of the dye can also be measured by using anodic stripping voltammetry preceded by adsorptive collection at ?0.7 V, but this procedure is less sensitive than CSV.     

Microfabricated disposable lab-on-a-chip sensors with integrated bismuth microelectrode arrays for voltammetric determination of trace metals

This work reports the fabrication of disposable three-electrode cells with integrated metal-film electrodes. The devices were fabricated by a multi-step micro-fabrication approach combining sputtering for the deposition of metals and the dielectric material (SiO₂) on the surface of a silicon wafer and photolithography for the definition of the geometry of the sensors. The working electrode was a microelectrode array consisting of bismuth microdisks while the reference and counter electrode strips were made of Ag and Pt, respectively. The utility of these devices was tested for the trace determination of Pb(II) and Cd(II) by anodic stripping voltammetry and Ni(II) by adsorptive stripping voltammetry. The detection of these trace metals was carried out in unstirred and undeoxygenated solutions exhibiting sub-μg L⁻¹ limits of detection and enhanced analytical characteristics compared to conventional bismuth-film electrodes.     

Polybenzoin Based Sensor for Determination of 2thiouracil in Biological Fluids and Pharmaceutical Formulations

A carbon paste electrode was modified by electropolymerisation of benzoin using voltammetric technique. A novel polybenzoin modified carbon paste electrode (PB‐CPE) was developed for use as a detector in cyclic voltammetry and differential pulse adsorptive stripping voltammetry for the sensitive determination of 2thiouracil (2TU). The atomic force microscopy was applied to characterize the surface morphology of PB‐CPE. The modified electrode showed excellent electrocatalytic activity for the oxidation of 2TU. The oxidation process was irreversible over the pH range studied and exhibited a diffusion controlled behavior. All experimental parameters have been optimized. The peak current for the stripping of 2TU was found to be linear over the concentration range of 0.2–1.2 µM, with a detection limit of 2.21 nM. The practical application of the PB‐CPE in the determination of 2TU in human biological fluids and pharmaceutical samples were demonstrated that it has high sensitivity and good selectivity.     

Determination of Cobalt Ions in Natural Waters Using Differential Pulse Adsorptive Stripping Voltammetry

Abstract

Differential pulse adsorptive stripping voltammetry using dimethylglyoxime complexes in the presence of triethanolamine and ammonium chloride can be applied to the determination of cobalt (II) ions in natural waters with high sensitivity. The limit of detection is about 3 ppt. Actual analysis of estuary water are reported. In this particular case of natural water, the factors influencing the use of differential pulse adsorptive stripping voltammetry for the determination of cobalt are described in detail.     

Square-wave adsorptive stripping voltammetry at glassy carbon electrode for selective determination of manganese. Application to some industrial samples

A new method to determine manganese by voltammetry after controlled adsorptive accumulation of the manganese–ammonium–acetate at the glassy carbon electrode is described. The manganese complex gives well-defined voltammetric peak at pH 4.0 and 9.0. Cathodic stripping voltammetry combined with the Osteryoung square-wave mode at the glassy carbon electrode gave rise to both sensitivity and selectivity of the determination of manganese in some industrial samples. The method offers enhanced sensitivity in comparison to analogous measurements presented in the literature. The detection limit with 5 min accumulation is 0.022 μg l⁻¹ . Simultaneous determination of manganese in presence of Cu(II), Pb(II) and Zn(II) could be easily done using anodic stripping voltammetry at pH 4.0. Calibration plots are constructed and the method was checked with the aid of standard industrial reference samples giving values of standard deviations between 1.2 and 1.8.     

Use of adsorptive square-wave anodic stripping voltammetry at carbon paste electrode for the determination of amlodipine besylate in pharmaceutical preparations

The antihypertensive drug amlodipine has been characterized voltammetrically in a carbon paste electrode by means of anodic stripping voltammetry. An adsorptive stripping method in a carbon paste electrode for trace determination of amlodipine has been described. Cyclic voltammetric studies indicated the oxidation of amlodipine besylate at the electrode surface through a single two-electron irreversible step fundamentally controlled by adsorption. A study of the variation in the peak current with solution variables such as pH, ionic strength, concentration of amlodipine, possible interference, and instrumental variables, such as preconcentration time and accumulation potential, has resulted in the optimization of the oxidation signal for analytical purposes. By anodic adsorptive anodic stripping voltammetry, the calibration plot was linear in the range 9.9 × 10^?9 ? 1.4 × 10^?7 M with a detection limit of 2 × 10^?10 M in a carbon paste electrode at pH 11.0. The procedure was successfully applied to the assay of amlodipine besylate in some commercial products in the market (Amlopres®, Amlodipine, and Norvasc®). The percentage recoveries were in agreement with those obtained by the reference method.     

Differentiation of Detection of Ascorbic Acid and Dehydroascorbic Acid Using Hydrodynamic Amperometry and Anodic Stripping Voltammetry on Modified Aluminum Electrodes

An electroanalytical strategy for the simultaneous determination of ascorbic acid (AA) and dehydroascorbic acid (DHA), is described. A palladized Al electrode is used for hydrodynamic amperometry of AA. While the decrease of anodic stripping voltammetry current of the K₂UO₂[Fe(CN)₆]‐Pd/Al electrode prepared in the presence of DHA was the principal of the DHA determination. The calibration graph for both methods was linear over the concentration range 1–50 μM. The detection limit was found to be 0.5 μM. Some fresh fruit juices and vegetables of trace level of AA and DHA were analyzed as the typical example of application.     

Cathodic stripping voltammetry of orotic acid (vitamin B13) at the hanging mercury drop electrode (HMDE)

Summary Controlled adsorptive accumulation of orotic acid (vitamin B₁₃) at the hanging mercury drop electrode (HMDE) provides the basis for the direct stripping measurement of that compound in nanomolar concentration. Differential pulse voltammetry applied to a sample at pH 11.20 fixed in NaOH has a detection limit of 5.0 × 10^–10 mol/l of orotic acid (with 3 min of preconcentration).The cathodic stripping response is evaluated with respect to experimental parameters such as preconcentration time, preconcentration potential, bulk concentration and other parameters. Cathodic stripping voltammetry can be proposed for the determination of the orotic acid, the reproducibility of this method was studied.

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Cathodic-Stripping Voltammetrie von Orotsäure (Vitamin B₁₃) an der hängenden Quecksilbertropfelektrode

     

Determination of trace amounts of morphine in human plasma by anodic adsorptive stripping differential pulse voltammetry

New adsorptive anodic differential pulse stripping voltammetry method for the direct determination of morphine at trace levels in human plasma of addicts is proposed.The procedure involves an adsorptive accumulation of morphine on a HMDE,followed by oxidation of adsorbed morphine by voltammetry scan using differential pulse modulation.The optimum conditions for the analysis of morphine are pH 10.5,Eacc of -100 mV（vs.Ag/AgCl）,and tacc of 120 s.The peak current is proportional to the concentration of morphine,and a Linear calibration graph is obtained at 0.01-3.10μg mL^-1.A relative standard deviation of 1.06%（n=5）was obtained,and the limit of detection was 3 ng mL^-1.The capabiLity of the method for the analysis of real samples was evaluated by the determination of morphine in spiked human plasma and addicts human plasma with satisfactory results.     

Differential pulse and square-wave cathodic stripping voltammetry of xanthine and xanthosine at a mercury electrode.

The surface activity of xanthine (Xan) and xanthosine (Xano) at a hanging mercury drop electrode (HMDE) was studied using out-of-phase ac and cyclic dc voltammetry. The results show that Xan and Xano were strongly adsorbed and chemically interacted with the charged mercury surface, which is the prerequisite step for applying the cathodic adsorptive stripping voltammetric determination of such biologically important compounds. Differential pulse cathodic adsorptive stripping voltammetry (DPCASV) and square-wave cathodic adsorptive stripping voltammetry (SWCASV) were applied for the ultratrace determination of Xan and Xano compounds. Moreover, a rapid and sensitive controlled adsorptive accumulation of Cu(II) complexes of both compounds provided the basis of a direct stripping voltammetric determination of such compounds to submicromolar and nanomolar levels. Operational and solution conditions for the quantitative ultratrace determination of Xan and Xano were optimized in absence and presence of Cu(II). The calibration curve data were subjected to least-squares refinements. The effects of several types of inorganic and organic interfering species on the determination of Xan or Xano were considered.