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).     

Electrochemical detection of sugar-related compounds using boron-doped diamond electrodes

Electrochemical detection of sugar-related compounds was conducted using a boron-doped diamond (BDD) electrode as a detector for flow-injection analysis (FIA). Sugar-related compounds oxidize at high applied potentials, for which the BDD electrode is suitable for electrochemical measurements. Conditions for an FIA system with a BDD detector were optimized, and the following detection limits were achieved for sugar-related compounds: monosaccharides, 25-100 pmol; sugar alcohols, 10 pmol; and oligosaccharides, 10 pmol. The detection limit for monosaccharide D-glucose (Glu) was 105 pmol (S/N = 3). A linear range was acquired from the detection limit to 50 nmol, and the relative standard deviation was 0.65% (20 nmol, n = 6). A high-performance liquid chromatography (HPLC) column was added to the system between the sample injector and the detector and detection limits to the picomole level were achieved, which is the same for the HPLC system and the FIA system. The electrochemical oxidation reaction of Glu was examined using cyclic voltammetry with the BDD detector. The reaction proved to be irreversible, and proceeded according to the following two-step mechanism: (1) application of a high potential (2.00 V vs. Ag/AgCl) to the electrode causes water to electrolyze on the electrode surface with the simultaneous generation of a hydroxyl radical on the surface, and (2) the hydroxyl radical indirectly oxidizes Glu. Thus, Glu can be detected by an increase in the oxidation current caused by reactions with hydroxy radicals.     

Electrochemical Detection of Clenbuterol in Pig Liver at Pyrrole-DNA Modified Boron-doped Diamond Electrode

Introduction Clenbuterol { 4-amino-[( tert-butylamino) meth-yl]-3,5-dichlorobenzyl alcohol hydrochloride} is aβ-agonist drug[1]. It can improve the ratio of muscle tofat when it is administrated with high doses to ani-mals[2,3]. However, the residues of clenbuterol(CL)are toxic to humans, leading to sickness and possibleheart complication[4]. It has been reported that CL iseasy to accumulate in animal livers.Recently, some analytical methods for the detec-tion of CL, such as HPLC[5], GC…     

Ta/BDD薄膜电极电化学催化氧化硝基酚

研究了热丝化学气相沉积法(HFCVD)制备得到钽衬底掺硼金刚石膜电极(Ta/BDD)的物理性质和电势窗口, 并考察了其用于电化学催化氧化硝基酚过程中的性能及各种影响因素. 扫描电镜和拉曼光谱表明, Ta/BDD电极具有良好的物理性能, 通过测试Ta/BDD电势窗口发现, 该电极具有较高的析氧过电位. 在Ta/BDD电化学催化氧化硝基酚过程中, 化学需氧量(COD)和高效液相色谱测试表明, 硝基酚能够有效降解, 电流密度、支持电解液及浓度对降解过程影响较大, 温度影响不明显. 强化寿命实验表明, Ta/BDD电极具有较好的稳定性. 实验结果表明, Ta/BDD电极是一种适于硝基酚降解和COD去除的优良电极.     

Use of nickel implanted boron-doped diamond thin film electrode coupled to HPLC system for the determination of tetracyclines

The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)-20% acetonitrile and detected at 1.55 V. The methods were validated over the concentration range 0.05-100 ppm with the overall average recoveries from 83.3 to 102.5% and R.S.D. of less than 10%. The proposed method was further applied to analyse shrimp samples.     

Electroanalysis of tetracycline using nickel-implanted boron-doped diamond thin film electrode applied to flow injection system.

The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated.     

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.     

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).     

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.     

Rapid Nanomolar Detection of Guaiacol from its Precursors Using a Core-shell Reversed-phase Column Coupled with a Boron-doped Diamond Electrode

The electrooxidation mechanisms of guaiacol (2-methoxyphenol), a food and beverage spoilage metabolite, and its precursors; vanillic acid (VA), vanillin, and ferulic acid (FA) were investigated by cyclic voltammetry (CV) with a boron-doped diamond (BDD) electrode. Reversed-phase liquid chromatography (RPLC) together with a BDD electrode poised at +1.6 V vs. Pd/H₂, was optimized for their sensitive detection. The separation was achieved in 60 s with a core-shell column (HALO C₁₈). The detection limits of these analytes ranged from 10–30 nM. The method was applicable for the analysis of guaiacol and its precursors from a popular commercial drink.     

Non-enzymatic electrochemical detection of glycerol on boron-doped diamond electrode

A non-enzymatic direct electrochemical glycerol detection method at a commercial boron-doped diamond (BDD) electrode in 0.1 M NaOH supporting electrolyte was developed. All the used electrochemical techniques proved useful features for the oxidation and direct amperometric determination of glycerol at a BDD electrode in 0.1 M NaOH aqueous solution. It was found that the direct electrooxidation of glycerol on the BDD electrode requires both adsorbed glycerol and hydroxyls at the electrode surface. Also, the sp(2) carbon did not allow enhancement of the glycerol oxidation process. The electronalytical sensitivity for the determination of glycerol at the BDD electrode ranged from 0.040 to 0.226 μA mM(-1) as a function of the technique used. The highest electroanalytical sensitivity for the determination of glycerol at the BDD electrode was reached in batch system amperometric quantification under stirring conditions. Performed recovery studies indicated that it is possible to determine glycerol in real samples, and the proposed batch system analysis-based methodology can be a valuable tool for practical glycerol analysis.     

Diamond Electrodes for High Sensitivity Mercury Detection in the Aquatic Environment: Influence of Surface Preparation and Gold Nanoparticle Activity

This work compares polished and unpolished boron doped diamond (BDD) electrodes decorated with two sizes of gold nanoparticles (AuNPs) for use as robust mercury sensors in aquatic environments. The size of the catalytically active AuNPs on the electrode surfaces was demonstrated to have a less significant effect on the sensitivity for mercury detection than the surface preparation of the BDD. The lowest limits of detection were achieved with the polished BDD electrodes, which both detected mercury at a concentration of 1 pM, six orders of magnitude greater sensitivity than the lowest detection limit of 5 μM achieved with an unpolished BDD electrode, and high in comparison with other reported electrode systems.     

Fabrication and electrochemical behaviour of vertically aligned boron-doped diamond nanorod forest electrodes

Vertically aligned boron-doped diamond nanorod forests (BDDNF) were successfully fabricated by depositing a diamond film onto silicon nanowires (SiNWs) using hot filament chemical vapor deposition (HFCVD). The boron-doped diamond nanorods were characterized by Raman spectroscopy and scanning electron microscopy (SEM). The BDDNF obtained from the SiNWs on the silicon wafer could be directly used as an electrode and its electrochemical behaviour is discussed here. Compared to a flat boron-doped diamond (BDD) electrode, the BDDNF electrode showed high sensitivity in the amperometric detection of adenine.     

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.     

Comparison of Boron‐Doped Diamond and Glassy Carbon Electrodes for Determination of Procaine Hydrochloride

The electrochemical oxidation of procaine hydrochloride (PC?HCL, 2‐diethylaminoethyl 4‐aminobenzoate hydrochloride) was investigated at as‐deposited boron‐doped diamond (ad‐BDD) electrode, anodically oxidized BDD (ao‐BDD) electrode and glassy carbon (GC) electrode using cyclic voltammetry (CV). Well‐defined cyclic voltammograms were obtained for PC?HCL oxidation with high signal‐to‐background (S/B) ratio, low tendency for adsorption, good reproducibility and long‐term stability at ad‐BDD electrode, demonstrating its superior electrochemical behavior and significant advantages in contrast to ao‐BDD and GC electrode. At 100 μM PC?HCL, the voltammetric S/B ratio was nearly one order of magnitude higher at an ad‐BDD electrode than that at a GC electrode. In a separate set of experiments for oxidation of 100 μM PC?HCL, 96%, 92% and 84% of the initial oxidation peak current was retained at the ad‐BDD, ao‐BDD and GC electrode, respectively, by stirring the solution after the tenth cycle. The current response was linearly proportional to the square root of the scan rate within the range 10–1000 mV s^?1 in 10 μM PC?HCL solutions, indicating that the oxidation process was diffusion‐controlled with negligible adsorption at an ad‐BDD surface. The good linearity was observed for a concentration range from 5 to 200 μM with a linear equation of y=0.03517x+0.65346 (r=0.999), and the detection limit was 0.5 μM for oxidation of PC?HCL at the ad‐BDD electrode. The ad‐BDD electrode could maintain 100% of its original activity after intermittent use for 3 months.     

Electrochemical impedance sensing of DNA hybridization on conducting polymer film-modified diamond

The impedimetric sensing of DNA hybridization on polyaniline/polyacrylate (PANI/PAA)-modified boron-doped diamond (BDD) electrode has been investigated. An ultrathin film of PANI-PAA copolymer was electropolymerized onto the diamond surfaces to provide carboxylic groups for tethering to DNA sensing probes. The electrochemical impedance and the intrinsic electroactivity of the polymer-diamond interface were analyzed after the hybridization reaction with target and non-target DNA. The impedance measurement shows changes in the impedance modulus as well as electron-transfer resistance at the stage of probe DNA immobilization (single-strand), as well as after hybridization with target DNA (double-strand). DNA hybridization increases the capacitance of the polymer-DNA layer and reduces the overall impedance of the DNA-polymer-diamond stack significantly. The polymer-modified BDD electrode shows no detectable nonspecific adsorption, with good selectivity between the complementary DNA targets and the one-base mismatch targets. The detection limit was measured to be 2 x 10(-8) M at 1000 Hz. Denaturing test on the hybridized probe and subsequent reuse of the probe indicates chemical robustness of the sensor. Our results suggest that electropolymerization followed by the immobilization of biomolecules is a simple and effective way of creating a functional biomolecular scaffold on the diamond surface. In addition, label-free electrochemical impedance method can provide direct and noninvasive sensing of DNA hybridization on BDD.     

Electrochemical oxidation of underivatized-nucleic acids at highly boron-doped diamond electrodes

Boron-doped diamond (BDD) electrodes have been examined for the electrochemical oxidation of underivatized-nucleic acids in terms of single stranded and double stranded DNA. Cyclic voltammetry and square wave voltammetry have been used to study the oxidation reactions and to detect DNA without derivatization or hydrolysis steps. At the diamond electrode, at least two well-defined voltammetric peaks were observed for both single stranded and double stranded DNA. Diamond electrode is the first material to show a well-defined voltammetric peaks for adenine group oxidation directly in the helix structure of nucleic acid due to its wide potential window. For single stranded DNA, a third peak, related to the pyrimidine group oxidation was also observed. As-deposited diamond film with predominantly hydrogen-terminated surface exhibited superior performance over oxygen-terminated diamond in terms of sensitivity. However, by optimizing the ionic strength, sensitivity of O-terminated films could be improved. Linear calibration results have shown linearity of current with concentration in the range 0.1-8 microg mL(-1) for both guanine and adenine residues at as-deposited BDD. Detection limits (S/N = 3) of 3.7 and 10 ng mL(-1) for adenine and guanine residue in single stranded DNA, respectively, and 5.2 and 10 ng mL(-1) for adenine and guanine residue in double stranded DNA, respectively, were observed. This work shows the promising use of diamond as an electrochemical detector for direct detection of nucleic acids. The results also show the possibility of using the oxidation peak current of adenine group that is more sensitive for the direct detection of nucleicacids.     

Electroanalysis of sulfonamides by flow injection system/high-performance liquid chromatography coupled with amperometric detection using boron-doped diamond electrode

Sulfonamides (SAs) were electrochemically investigated using cyclic voltammetry at a boron-doped diamond (BDD) electrode. Comparison experiments were carried out using a glassy carbon electrode. The BDD electrode provided well-resolved oxidation, irreversible cyclic voltammograms and higher current signals when compared to the glassy carbon electrode. Results obtained from using the BDD electrode in a flow injection system coupled with amperometric detection were illustrated. The optimum potential from a hydrodynamic voltammogram was found to be 1100 mV versus Ag/AgCl, which was chosen for the HPLC-amperometric system. Excellent results of linear range and detection limit were obtained. This method was also used for determination of sulfonamides in egg samples. The standard solutions of 5, 10, and 15 ppm were spiked in a real sample, and percentage of recoveries was found to be between 90.0 and 107.7.     

The Determination of Methanol Using an Electrolytically Fabricated Nickel Microparticle Modified Boron Doped Diamond Electrode

A nickel modified boron doped diamond (Ni‐BDD) electrode and nickel foil electrode were used in the determination of methanol in alkaline solutions. The Ni‐BDD electrode was electrodeposited from a 1 mM Ni(NO₃)₂ solution (pH 5), followed by repeat cycling in KOH. Subsequent analysis utilised the Ni(OH)₂/NiOOH redox couple to electrocatalyse the oxidation of methanol. Methanol was determined to limits of 0.3 mM with a sensitivity of 110 nA/mM at the Ni‐BDD electrode. The foil electrode was less sensitive achieving a limit of 1.6 mM and sensitivity of 27 nA/mM. SEM analysis of the electrodes found the Ni‐BDD to be modified by a quasi‐random microparticle array.     

Electrochemical detection of ascorbic acid and serotonin at a boron-doped diamond electrode modified with poly(N,N-dimethylaniline)

The electrochemical oxidation of ascorbic acid (AA) and serotonin (5-HT) at a boron-doped diamond (BDD) electrode modified with poly(N,N-dimethylaniline) (PDMA) has been studied. The oxidation potentials of 5-HT and AA overlapped after mixing of the two chemicals, due to interference of AA at the bare BDD electrode. However, after modifying the BDD electrode with a cationic polymer (PDMA), the oxidation peaks of 5-HT and AA were separated. PDMA-coated BDD electrodes can be used for simultaneous detection of these species.