Sensitive Electrochemical Detection of Oxalate at a Positively Charged Boron‐Doped Diamond Surface

Allyltriethylammonium bromide (ATAB) was covalently attached to the surface of hydrogen‐terminated boron‐doped diamond (BDD) thin films using a photochemical method to fabricate positively charged electrode surfaces. The anodic current for oxalate oxidation both in cyclic voltammetry and in flow‐injection analysis with amperometry was found to be up to two times larger at ATAB‐modified BDD (ATAB‐BDD) than at an unmodified BDD electrode, which may be based on the electrostatic interaction between the oxalate anion and the electrode surface. In addition, the stability of the electrochemical detection of oxalate was improved at the ATAB‐BDD electrode compared to the unmodified electrode.     

Simultaneous detection of purine and pyrimidine at highly boron-doped diamond electrodes by using liquid chromatography

Highly boron-doped diamond (BDD) electrode, have been examined for simultaneous detection of purine and pyrimidine bases in mild acidic media by using HPLC with amperometric detection. Cyclic voltammetry at as-deposited (AD) and anodically oxidized (AO) BDD were used to study the electrochemistry and to optimize the condition for HPLC applications. At AO BDD electrode, due to its higher overpotential of oxygen evolution reaction, well-defined anodic peaks were observed for the oxidation of purine and pyrimidine bases in acid medium, whereas at AD BDD the oxidation peak of thymine was overlapped with the anodic current of oxygen evolution. The chromatograms of adenine, guanine, cytosine, thymine and 5-methylcytosine mixture were well resolved by using a silica-based column and a solution of 5% acetonitrile in 100 mM ammonium acetate buffer (pH 4.25) as the mobile phase. The detection was carried out at AO BDD electrode at an applied potential of 1.6 V versus Ag/AgCl. Linear calibration curves were obtained within the concentration range from 0.1 to 10 μM with the limits of detection (S/N = 3) ranging from 26.3 to 162.1 nM, resulting in an order of magnitude higher sensitivities than those at conventional electrodes. HPLC analysis with diamond amperometric detector was successfully applied for determination of 5-methylcytosine in real DNA samples with high reproducibility. No deactivation of the electrode was found during cyclic voltammetric and HPLC measurements, indicating the high stability for analysis of biological samples.     

Electroanalytical Determination of Cadmium(II) and Lead(II) Using an Antimony Nanoparticle Modified Boron‐Doped Diamond Electrode

We report the simultaneous electroanalytical determination of Pb²⁺ and Cd²⁺ by linear sweep anodic stripping voltammetry (LSASV) using an antimony nanoparticle modified boron doped diamond (Sb‐BDD) electrode. Sb deposition was performed in situ with the analytes, from a solution of 1 mg L^?1 SbCl₃ in 0.1 M HCl (pH 1). Pb²⁺ inhibited the detection of Cd²⁺ during simultaneous additions at the bare BDD electrode, whereas in the presence of antimony, both peaks were readily discernable and quantifiable over the linear range 50–500 μg L^?1.     

Anodic stripping voltammetry of antimony at unmodified carbon electrodes

Antimony is an element of significant environmental concern, yet has been neglected relative to other heavy metals in electroanalysis. As such very little research has been reported on the electroanalytical determination of antimony at unmodified carbon electrodes. In this paper we report the electrochemical determination of Sb(III) in HCl solutions using unmodified carbon substrates, with focus on non-classical carbon materials namely edge plane pyrolytic graphite (EPPG), boron doped diamond (BDD) and screen-printed electrodes (SPE). Using differential pulse anodic stripping voltammetry, EPPG was found to give a considerably greater response towards antimony than other unmodified carbon electrodes, allowing highly linear ranges in nanomolar concentrations and a detection limit of 3.9?nM in 0.25?M HCl. Furthermore, the sensitivity of the response from EPPG was 100 times greater than for glassy carbon (GC). Unmodified GC gave a comparable response to previous results using the bare substrate, and BDD gave an improved, yet still very high limit of detection of 320?nM compared to previous analysis using an iridium oxide modified BDD electrode. SPEs gave a very poor response to antimony, even at high concentrations, observing no linearity from standard additions, as well as a major interference from the ink intrinsic to the working electrode carbon material. Owing to its superior performance relative to other carbon electrodes, the EPPG electrode was subjected to further analytical testing with antimony. The response of the electrode for a 40?nM concentration of Sb(III) was reproducible with a mean peak current of 1.07?µA and variation of 8.4% (n?=?8). The effect of metals copper, bismuth and arsenic were investigated at the electrode, as they are common interferences for stripping analysis of antimony.     

Sensitive Detection of Capsaicin by Adsorptive Stripping Voltammetry at a Boron‐Doped Diamond Electrode in the Presence of Sodium Dodecylsulfate

In the present paper, a sensitive electroanalytical methodology for the determination of capsaicin using adsorptive stripping voltammetry (AdSV) at a boron‐doped diamond (BDD) electrode is presented. The voltammetric results indicate that in the presence of sodium dodecylsulfate (SDS) the BDD electrode remarkably enhances the oxidation of capsaicin which leads to an improvement of the peak current with a shift of the peak potential to less negative values. A linear working range of 0.05 to 6.0 µg mL^?1 (0.16–20 µM) with a detection limit of 0.012 µg mL^?1 (0.034 µM) has been obtained using BDD electrode by AdSV.     

A Batch Injection Analysis System with Square-wave Voltammetric Detection for Fast and Simultaneous Determination of Zinc and Ascorbic Acid

The determination of organic and inorganic compounds in a single run is still a great challenge. In this paper, we developed a method for fast simultaneous determination of ascorbic acid (AA) and zinc ions (Zn) using batch injection analysis with detection by square-wave anodic stripping voltammetry (BIA-SWASV). Britton-Robinson (BR) buffer solution (pH=6.0) as the supporting electrolyte and boron doped diamond (BDD) as the working electrode. The method presented favorable analytical characteristics such as fast response (67 injections h⁻¹), low detection limits (0.2 and 5.4 μmol L⁻¹ for Zn ions and AA, respectively) and recovery values of 99±3%.     

The Fabrication and Characterization of a Bismuth Nanoparticle Modified Boron Doped Diamond Electrode and Its Application to the Simultaneous Determination of Cadmium(II) And Lead(II)

We report the simultaneous electroanalytical determination of Pb²⁺ and Cd²⁺ by square‐wave anodic stripping voltammetry (SWASV) using a bismuth nanoparticle modified boron doped diamond (Bi‐BDD) electrode. Bi deposition was performed in situ with the analytes, from a solution of 0.1 mM Bi(NO₃)₃ in 0.1 M HClO₄ (pH 1.2), and gave detection limits of 1.9 μg L^?1 and 2.3 μg L^?1 for Pb(II) and Cd(II) respectively. Pb²⁺ and Cd²⁺ could not be detected simultaneously at a bare BDD electrode, whilst on a bulk Bi macro electrode (BiBE) the limits of detection for the simultaneous determination of Pb²⁺ and Cd²⁺ were ca. ten times higher.     

A Nitrite Electrochemical Sensor Based on Boron‐Doped Diamond Planar Electrochemical Microcells Modified with a Monolacunary Silicotungstate Polyoxoanion

A new boron doped diamond microcells (BDD) was modified, for rapid, selective and highly sensitive determination of nitrite, using a coating film of polyoxometalates (POMs), formed by cyclic voltammetry on the molecular p‐phenylenediamine (PPD) functionalized BDD. The scanning electron microscopy (SEM) technique was used to examine the morphology of (PPD/SiW₁₁) modified (BDD) electrode. It was found that (SiW₁₁) layer was uniformly formed on the electrode surface. It was observed that (BDD/PPD/SiW₁₁) showed excellent electrocatalytic activities towards nitrite ion. Under the selected conditions, the anodic peak maximum at ?0.6 V was linear versus nitrite concentration in the 40 µM–4 mM range, and the detection limit obtained was 20 µM. The newly developed electrode has been successfully applied to the determination of nitrite content in real river water samples.     

Electrochemical Quantification of Mercury in Solutions Using Boron-doped Diamond Electrodes: Electrode Regeneration and Role of Gold and Impurities

Abstract

For determining Hg in solutions in the ppb to ppt range using boron-doped diamond (BDD) electrochemistry, the role of an added gold solution for enhanced sensitivity is investigated. Using differential pulse anodic stripping voltammetry (DPASV), peaks due to Cu and Ag as impurities from gold are identified. With the proper choice of the potential for deposition, effects of the impurities are minimized and an electrode regeneration procedure is devised and tested, resulting in reproducible slopes of the calibration curves in successive runs. The location and shift of the DPASV peak potentials with concentration are explained with the use of the Nernst equation.     

Anodic Stripping Voltammetry Determination of Pb(II) and Cd(II) at a Bismuth/Poly(aniline) Film Electrode

Abstract

A novel voltammetric method—anodic—using a bismuth/poly(aniline) film electrode has been developed for simultaneous measurement of Pb(II) and Cd(II) at low µg L^?1 concentration levels by stripping voltammetry. The results confirmed that the bismuth/poly(aniline) film electrode offered high‐quality stripping performance compared with the bismuth film electrode. Well‐defined sharp stripping peaks were observed for Pb(II) and Cd(II), along with an extremely low baseline. The detection limits of Pb(II) and Cd(II) are 1.03 µg L^?1 and 1.48 µg L^?1, respectively. The bismuth/poly (aniline) electrode has been applied to the determination of Pb(II) in tap water samples with satisfactory results.     

Manganese detection in marine sediments: anodic vs. cathodic stripping voltammetry

Three different electroanalytical techniques for the detection of manganese in marine sediments are evaluated. The anodic stripping voltammetry of manganese at an in situ bismuth-film-modified boron-doped diamond electrode and cathodic stripping voltammetry at a carbon paste electrode are shown to lack the required sensitivity and reproducibility whereas cathodic stripping voltammetry at a bare boron-doped diamond electrode is shown to be reliable and selective with a limit of detection, from applying a 60 s accumulation period of 7.4 × 10⁻⁷ M and a sensitivity of 0.24 A M⁻¹. The method was used to evaluate the manganese content of marine sediments taken from Šibenik, Croatia.     

Electrochemical analysis of -penicillamine using a boron-doped diamond thin film electrode applied to flow injection system

The electroanalysis of -penicillamine in 0.1 phosphate buffer (pH 7) was studied at a boron-doped diamond thin film (BDD) electrode using cyclic voltammetry as a function of concentration of analyte and pH of analyte solution. Comparison experiments were performing using a glassy carbon (GC) electrode. The BDD electrode exhibited a well-resolved and irreversible oxidation voltammogram, but the GC electrode provided only an ill-defined response. The BDD electrode provided a linear dynamic range from 0.5 to 10 mM and a detection limit of 25 μM (S/B≥3) in voltammetric measurement. It was also found that the peak potentials were decreased when the pH of the analyte solution was increased. In addition, penicillamine has been studied by hydrodynamic voltammetry and flow injection analysis with amperometric detection using the BDD electrode. The flow injection analysis results at the diamond electrode indicated a linear dynamic range from 0.5 to 50 μM and a detection limit of 10 nM (S/N≈4). The proposed method was applied to determine -penicillamine in dosage form (capsules), the results obtained in the recovery study (255±2.50 mg per tablet) were comparable to those labeled (250 mg per tablet).     

Electrochemical analysis of d-penicillamine using a boron-doped diamond thin film electrode applied to flow injection system

The electroanalysis of d-penicillamine in 0.1 phosphate buffer (pH 7) was studied at a boron-doped diamond thin film (BDD) electrode using cyclic voltammetry as a function of concentration of analyte and pH of analyte solution. Comparison experiments were performing using a glassy carbon (GC) electrode. The BDD electrode exhibited a well-resolved and irreversible oxidation voltammogram, but the GC electrode provided only an ill-defined response. The BDD electrode provided a linear dynamic range from 0.5 to 10 mM and a detection limit of 25 muM (S/B>/=3) in voltammetric measurement. It was also found that the peak potentials were decreased when the pH of the analyte solution was increased. In addition, penicillamine has been studied by hydrodynamic voltammetry and flow injection analysis with amperometric detection using the BDD electrode. The flow injection analysis results at the diamond electrode indicated a linear dynamic range from 0.5 to 50 muM and a detection limit of 10 nM (S/N approximately 4). The proposed method was applied to determine d-penicillamine in dosage form (capsules), the results obtained in the recovery study (255+/-2.50 mg per tablet) were comparable to those labeled (250 mg per tablet).     

Edge Plane Pyrolytic Graphite Electrodes for Stripping Voltammetry: a Comparison with Other Carbon Based Electrodes

The first examples of using edge plane pyrolytic graphite electrodes for anodic and cathodic stripping voltammetry (ASV and CSV) are presented, notably the ASV of silver and the CSV of manganese. In the former example, detection limits for silver (based on 3σ) of 8.1 nM and 0.185 nM for 120 s and 300 s accumulation time, respectively, were achievable using the edge plane electrode, which were superior to those observed on glassy carbon, basal plane pyrolytic graphite and boron‐doped diamond electrodes. In the second example, a detection limit for manganese of 0.3 μM was possible which was comparable with that achievable with a boron‐doped diamond electrode but with an increased sensitivity. Comparison of the edge plane pyrolytic graphite electrode with boron‐doped diamond electrodes reveals that the edge plane electrode has comparable detection limits and sensitivities whilst exhibiting a lower signal‐to‐noise ratio and large potential window for use in trace analysis suggesting boron‐doped diamond can be conveniently replaced by edge plane pyrolytic graphite as an electrode material in many applications.     

Amorphous carbon nitride as an alternative electrode material in electroanalysis: Simultaneous determination of dopamine and ascorbic acid

Boron-doped diamond (BDD) films are excellent electrode materials, whose electrochemical activity for some analytes can be tuned by controlling their surface termination, most commonly either to predominantly hydrogen or oxygen. This tuning can be accomplished by e.g. suitable cathodic or anodic electrochemical pretreatments. Recently, it has been shown that amorphous carbon nitride (a-CN_x) films may present electrochemical characteristics similar to those of BDD, including the influence of surface termination on their electrochemical activity toward some analytes. In this work, we report for the first time a complete electroanalytical method using an a-CN_x electrode. Thus, an a-CN_x film deposited on a stainless steel foil by DC magnetron sputtering is proposed as an alternative electrode for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) in synthetic biological samples by square-wave voltammetry. The obtained results are compared with those attained using a BDD electrode. For both electrodes, a same anodic pretreatment in 0.1 mol L⁻¹ KOH was necessary to attain an adequate and equivalent separation of the DA and AA oxidation potential peaks of about 330 mV. The detection limits obtained for the simultaneous determination of these analytes using the a-CN_x electrode were 0.0656 μmol L⁻¹ for DA and 1.05 μmol L⁻¹ for AA, whereas with the BDD electrode these values were 0.283 μmol L⁻¹ and 0.968 μmol L⁻¹, respectively. Furthermore, the results obtained in the analysis of the analytes in synthetic biological samples were satisfactory, attesting the potential application of the a-CN_x electrode in electroanalysis.     

Biofouling and in situ electrochemical cleaning of a boron-doped diamond free chlorine sensor

Biofouling presents a significant obstacle to the long-term use of electrochemical sensors in complex media. Drinking water biofilms reduce performance of sensors by insulating electrode surfaces by inter alia inhibiting mass transport. Boron-doped diamond (BDD) electrodes are relatively resistant to biofouling and inert at high potentials. These qualities can be exploited to create a drinking water quality sensor that resists biofouling to meet performance criteria for longer, and to enable electrochemical cleaning of the sensor surface in situ using high potentials without disconnecting or disassembling the sensor.A purpose-built BDD wall-jet sensor was compared with a glassy carbon (GC) sensor in ability to determine free chlorine, detect biofilm and remove biofilm in situ. It was found that the BDD produced accurate and reliable readings with a 4.86% standard error and a LOD of 0.18 ppm. The BDD could be electrochemically cleaned in situ whereas this was less successful with the GC electrode. The BDD electrode could also detect electroactive pyocyanin, secreted in the biofilm of the drinking water biofilm indicator organism Pseudomonas aeruginosa, potentially enabling biofouling and non-biological fouling such as scaling to be distinguished. Observed changes in flow sensitivity and current-voltage curves that correspond to fouling provide multiple fouling detection methods, resulting in an accurate, sensitive, water quality sensor that can be cleaned without disassembly or replacement of parts and can identify when cleaning is required.     

Highly sensitive determination of mercury using copper enhancer by diamond electrode coupled with sequential injection–anodic stripping voltammetry

A highly sensitive determination of mercury in the presence of Cu(II) using a boron-doped diamond (BDD) thin film electrode coupled with sequential injection–anodic stripping voltammetry (SI–ASV) was proposed. The Cu(II) was simultaneously deposited with Hg(II) in a 0.5 M HCl supporting electrolyte by electrodeposition. In presence of an excess of Cu(II), the sensitivity for the determination of Hg(II) was remarkably enhanced. Cu(II) and Hg(II) were on-line deposited onto the BDD electrode surface at −1.0 V (vs. Ag/AgCl, 3 M KCl) for 150 s with a flow rate of 14 μL s⁻¹. An anodic stripping voltammogram was recorded from −0.4 V to 0.25 V using a frequency of 60 Hz, an amplitude of 50 mV, and a step potential of 10 mV at a stopped flow. Under the optimal conditions, well-defined peaks of Cu(II) and Hg(II) were found at −0.25 V and +0.05 V (vs. Ag/AgCl, 3 M KCl), respectively. The detection of Hg(II) showed two linear dynamic ranges (0.1–30.0 ng mL⁻¹ and 5.0–60.0 ng mL⁻¹). The limit of detection (S/N = 3) obtained from the experiment was found to be 0.04 ng mL⁻¹. The precision values for 10 replicate determinations were 1.1, 2.1 and 2.9% RSD for 0.5, 10 and 20 ng mL⁻¹, respectively. The proposed method has been successfully applied for the determination of Hg(II) in seawater, salmon, squid, cockle and seaweed samples. A comparison between the proposed method and an inductively coupled plasma optical emission spectrometry (ICP-OES) standard method was performed on the samples, and the concentrations obtained via both methods were in agreement with the certified values of Hg(II), according to the paired t-test at a 95% confidence level.     

Adsorptive Stripping Voltammetric Determination of Trace Level Ricin in Castor Seeds Using a Boron‐doped Diamond Electrode

Ricin, (Ricinus communis agglutinin, RCA) is one of the most poisonous of naturally occurring substances and has great potential for bioterrorism because no antidote exists. Fast detection at low concentrations is a challenge, and vital to the development of proper countermeasures. In this study, a square wave adsorptive stripping voltammetric (SWAdSV) method for determining RCA using a cathodically polarized boron‐doped diamond (BDD) electrode is presented. An irreversible electrochemical RCA oxidation peak was identified on the BDD electrode by different voltammetric techniques using both direct and adsorptive stripping modes. An adsorption‐controlled (slope log Ip vs log v of 0.80) pH‐dependent process was observed. For values of 1.0≤pH≤9.0, the numbers of protons and electrons associated with the oxidation reaction were estimated (ca. 1.0) by differential pulse voltammetry. The RCA oxidation step may correspond to the oxidation of tryptophan amino acid residues, and occurs in a complex mechanism. The excellent analytical performance of the cathodically polarized BDD electrode in combination with the stripping mode ramp was verified with RCA by using a short deposition time in an open circuit potential (120 s). Under optimized analysis conditions, a linear response in the range of (3.3–94.0)×10⁻⁹ mol L⁻¹ (r²=0.9944) and a limit of detection of 6.2×10⁻¹⁰ mol L⁻¹ were estimated. This LOD is lower than several methods found in the literature. For example, it is 168 times lower than that obtained by using square wave voltammetric with a glassy carbon electrode. Moreover, an even lower LOD might be achieved by using the SWAdSV method with a higher pre‐concentration time. In addition, trace levels of RCA were successfully determined in different castor seed cultivars with an overall average recovery from 99.2±1.6 % for the three different RCA‐A concentration levels. The high accuracy of the analytical data highlights the use of the proposed method for determining RCA in other samples.     

Fabrication of Pt nanoparticles-decorated CVD diamond electrode for biosensor applications

An electrochemical biosensor was developed using boron-doped diamond (BDD) as an electrode material. To enhance the electrical performance of the electrode, the BDD electrode was decorated with Pt-nanoparticles (Pt-NPs) by electrochemical deposition. Their morphology according to the applied potentials for the synthesis of Pt-NPs was characterized by SEM. To identify the performance of the electrode modified with Pt-NPs, glucose detection was used as a sample sensing process, and the results were compared with those of a gold electrode and a bare BDD electrode. The electrochemical characteristics of the modified electrode were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The BDD electrode with the Pt-NPs showed higher sensitivity and a lower detection limit than the Au electrode and BDD electrode. The proposed biosensor based on the Pt-NPs decorated BDD electrode showed high sensitivity, a low detection limit, fast direct electron transfer and good stability.     

Sonoelectrochemical investigation of silver analysis at a highly boron-doped diamond electrode

A study into the sonoelectroanalysis of silver at a highly boron-doped diamond electrode is presented, exploring the benefits of the introduction of power ultrasound and new electrode materials into classical electrochemical techniques. Both cathodic and anodic stripping voltammetry have been investigated in terms of their analytical suitability towards silver detection. Cathodic stripping voltammetry, via electrodeposited silver oxide, was affected by the unusual chemistry of the highly oxidising Ag(2+) species and the characterisation of this system is discussed in detail. Anodic stripping, via deposition of metallic silver on the bare boron-doped diamond electrode surface under ultrasound, coupled with square-wave voltammetry, was successfully employed in the development of a sensitive technique for the analysis of trace silver ions. A detection limit for Ag(+) of 10(-9) M for a 300-s deposition, with a linear range of at least two orders of magnitude, and the beneficial effects of controlling the speciation of Ag(+) via complexation with chloride ions are reported.