Differential Pulse Voltametry Research Articles

A molecularly imprinted electrochemical sensor MIP/Cu-MOF/rGO/AuNPs/GCE for highly sensitive detection of electroneutral organophosphorus pesticide residues.

A novel electrochemical sensor, MIP/Cu-MOF/rGO/AuNPs/GCE, was developed by depositing gold nanoparticles, coating Cu-MOF/GO on the surface of glassy carbon electrode (GCE) before electroreducing graphene oxide (GO) to rGO and covering molecularly imprinted membrane by electropolymerization for highly sensitive detection of electroneutral organophosphorus pesticide residues in agricultural product. Cyclic voltammetry, differential pulse voltametry, scanning electron microscopy, energy-dispersive spectroscopy, and atomic force microscopy were used to characterize the imprinted sensor. Several key factors such as chitosan concentration, suspension volume, pH of polymerization solution, and polymerization scanning rate during preparation of the imprinted sensor were optimized in detail. When electroneutral phosmet was used as a template, the linear range of MIP/Cu-MOF/rGO/AuNPs/GCE for detecting phosmet was 1.00 × 10-14-5.00 × 10-7 mol/L with the limit of detection of 7.20 × 10-15 mol/L at working potentials of - 0.2 to 0.6 V. The selectivity, reproducibility, and repeatability of MIP/Cu-MOF/rGO/AuNPs/GCE were all acceptable. The recoveries of this method for determining phosmet in real samples ranged from 94.2 to 106.5%. The MIP/Cu-MOF/rGO/AuNPs/GCE sensor could be applied to detect electroneutral pesticide residues in organisms and agricultural products.

Synthesis, characterization and structure of novel Vanadium (III) complexes: Investigation of electrochemical application

From the prospective of possible electrochemical application of vanadium complexes, here, we report the two novel vanadium complexes. Namely, Tp*VO(3,5-Me2pzH)2(CH3CN) (1) (where, Tp* = hydro tris(3,5-dimethylpyrazolyl)borate and Tp*VTp*(2) these complexes were prepared in a good yield starting from V(III) chloride and hydro tris (3, 5 dimethyl pyrazolyl) borate. Both the complexes were characterized by NMR, Mass, and FTIR spectroscopy. In addition, cyclic voltammetry is used to investigate electrochemical processes of 1 and 2. The electrochemical active species exhibits two noteworthy redox peaks and exhibits considerable catalytic action towards glassy carbon electrodes with a composite of multi-walled carbon nanotubes (MWCNTs). Moreover, the complex1/MWCNTs/GC electrode detects the H2O2 in PBS (pH 7) electrolyte solution by cyclic voltametry (CA), differential pulse voltametry (DPV) and chronoamperometry (CA) techniques; Under the optimal conditions, the reduction peak current is linear to the H2O2 concentration in the ranges, detection limit for; CA: 50–500 μmol; 4.5 μmol L−1, CV: 50–400 μmol; 9.5 μmol L−1, DPV: 50–500 μmol; 8.3 μmol L−1. Single-crystal XRD analysis revealed that complex 1 crystallized in the orthorhombic space group P212121with lattice parameters a = 11.960(4) Å, b = 12.571(4) Å, c = 20.465(7)Å, Z = 4. In addition, distorted octahedral geometry was observed around the vanadium metal centre. Surface morphology of the complexes was probed by scanning electron microscopy (SEM).

Synthesized Cobalt Tetroxide-Graphene Composite Film by Electrospinning and Modified Glassy Carbon Electrode for Ofloxacin Determination

The purpose of this study was to determinate ofloxacin, the approach of electrospinning and electrochemical was adopted, metal oxide cobalt tetroxide (Co3O4)/graphene (GR) nanomaterials were electrodeposited on the surface of glassy carbon electrode, then prepared a new type of nanocomposite electrode (Co3O4/GR/GCE), it was successfully used to measure ofloxacin. The experiments show that the surface morphology of the modified electrode was characterized by scanning electron microscopy, and the Co3O4 nanoparticles and GR could be well modified on the surface of the glassy carbon electrode. The determination conditions of ofloxacin were optimized by the differential pulse voltametry (DPV). Under the optimal conditions, the linear relationship ranged from 0.45 to 170 μM, and the minimum detection limit was 0.16 μM (S/N = 3). Moreover, the recovery rate in the actual drug was good, and the relative standard deviations were all less than 5%. The impacts of the obtained results indicate that the modified electrode has good electrocatalytic performance for ofloxacin, and has good repeatability and practicability, and can significantly improve the detection sensitivity.

Molecularly imprinted electrochemical sensing platform for 2-Aminoadipic acid, a diabetes biomarker

A silylatedgraphene oxide (Si-GO) based electrochemical sensor was fabricated for the selective and specific detection of a diabetes biomarker 2-Aminoadipic Acid (2-AAA). The fabrication was preceded by molecularly imprinting technology accompanied by electrochemical sensing. Different molecularly imprinted polymers (MIPs) were prepared using different monomers such as 2-Acrylamido-2-methylpropanesulfonicacid (AMPS), Methacrylic acid (MAA) and Vinyl pyridine (VPy) with different ratios. Ethylene glycol dimethacrylate (EGDMA) and potassium peroxodisulphate (KPS) were used as a cross linker and an initiator, respectively. Cyclic voltametry (CV), differential pulse voltametry (DPV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the modified electrode. Modified electrode can be prepared by the surface modification of a glassy carbon electrode (GCE) with MIP (MIP/GCE) by drop-casting method. The prepared materials were characterized using Fourier Transforms Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). The modified MIP electrode shows an enhanced redox peak with a peak potential difference of 0.70 V with redox current of 0.015 mA, which indicates the presence of complementary active sites of 2-AAA in MIP. The NIP electrode shows a weaker redox peak difference compared to MIP. The optimum time response and pH were found to be 15 min and 5, respectively. DPV analysis gives good linearity with R2 value 0.9932. Limit of detection (LOD) and Limit of quantification (LOQ) were obtained as 0.40 × 10−11 and 1.34 × 10−11 M, respectively.

Mannich reaction derived phthalocyanine polymer for electrochemical detection of salicylic acid

The Mannich base derived polymeric cobalt phthalocyanine poly(CoTAPOPMPPc) was synthesized via three steps viz., i) formation of Mannich base, ii) conversion of Mannich base to oxy bridged phthalonitrile ligand and iii) the cyclotetramerization of oxy bridged phthalonitrile ligand to form polymeric phthalocyanine. The synthesized compounds were in pure state and have been characterized using various physicochemical and analytical techniques. The synthesized polymeric phthalocyanine poly(CoTAPOPMPPc) was immobilized on the glassy carbon electrode and characterised. The carbon nanoparticles (KB) were used for the fabrication of composite electrode GCE/KB-poly(CoTAPOPMPPc) and employed for the detection of salicylic acid (SA) using voltammetry and differential pulse voltametry (DPV). DPV peaks were well-resolved than the peaks observed in the CV. The DPV technique displayed linear response in the range 5–120 μM with limit of detection (LOD) 2 and 1.5 μM and sensitivity 0.0690 and 5.9957 μA μM−1 cm−2 at GCE/poly(CoTAPOPMPPc) and GCE/KB-poly(CoTAPOPMPPc), respectively. The chronoamperometry showed linear range between 0.5 and 4.5 μM salicylic acid with LOD of 0.18 and 0.12 μM with sensitivity of 1.7788 and 8.8245 μA μM−1 cm−2 at GCE/poly(CoTAPOPMPPc) and GCE/KB-poly(CoTAPOPMPPc) electrodes respectively. In addition to better electrocatalytic response for salicylic acid, GCE/KB-poly(CoTAPOPMPPc) did not show response for co-existing molecules inferring a selective response for salicylic acid. The proposed sensor demonstrated better sensing parameters and could be applied in the real sample analysis of SA.

Zinc ion-imprinted polymer based on silica particles modified carbon paste electrodes for highly selective electrochemical determination of zinc ions

ABSTRACT In this study, Zn(II) ion-imprinted polymer was prepared on the surface of vinyl silica particles and applied for detection of Zn(II) ions using differential pulse voltametry. The ion- imprinted polymer particles were prepared by free radical polymerization. The prepared particles were characterized by different morphological and elemental techniques. The ion-imprinted particles were used to fabricate the carbon paste electrode as a zinc ions sensor. The modified zinc sensor showed linear response in the concentration range 6.12 × 10−9 to 4.59 × 10−8 mol L−1. The limit of detection and limit of quantification of the electrode were 1.351 × 10−8 and 4.094 × 10−8 mol L−1, respectively.

Electrochemical sensing of hydrogen peroxide using brominated graphene as mimetic catalase

Recently we have reported the peroxidase mimicking ability of metal free brominated graphene (GBR) (Analytical Chemistry, 89, 783–791, 2017) at a pH less than 7.2. Here we report the novel catalase mimicking ability of GBR via electrochemical (electro-oxidation) detection of hydrogen peroxide (H2O2) at pH ≥ 7.2. We have fabricated successfully a low cost electrochemical sensor using GBR coated glassy carbon electrode (GCE) [(GBR-GCE)-working electrode] and showed its excellent cyclic voltametry (CV) response towards electro-oxidation of hydrogen peroxide (H2O2), which is so far shown by electrodes made of platinum-group metals like Pt, Ir, Ru etc. Thus, GBR has exhibited the dual mimicking ability as peroxidase and also as catalase under different conditions. A plausible mechanism of sensing of hydrogen peroxide has been proposed involving the formation of perhydroxyl radical (HO2˙) facilitated by GBR-GCE as the electrode. Calibration curves for H2O2 detection using both CV and differential pulse voltametry (DPV) techniques have been constructed over 0.1–10 mM linearity range with the limits of detection of 0.048 and 0.063 mM, respectively. This fabricated electrochemical sensor is highly selective, specific and its response current is least affected by the presence of interfering analytes. The results are found highly reproducible and the use of GBR has also minimized the problem and specificity associated with natural enzymes, as it can easily be stored at room temperature. Real samples have also been successfully analyzed using our fabricated sensor.

Determination of Curcumin in Turmeric Sample Using Edge Plane Pyrolytic Graphite Electrode

Phenolic compounds are an important class of the antioxidants and found in several natural products. Research on the phenolic compounds having antioxidant properties present in natural pruducts like fruits, spices and herbs are increased in recent years. Electroanalytical methods have low detection limits very short analysis time and require less budge as well. These advantages make the electroanalytical methods favorable and voltammetric analysis methods are one of the preferred methods in determination of the compounds having antioxidant properties present in different matrices. In this study, curcumin in turmeric samples were quantitatively determined by using edge plane pyrolytic graphite electrode (EPPG) and differential pulse voltammetry. Electrooxidation behaviour of curcumin was also examined by using cyclic voltammetry method. A three electrode electrochemical cell was used for voltammetric analysis. Edge plane pyrolitic graphite (EPPG), was used as working electrode, saturated calomel electrode (SCE) was used as reference electrode and Pt wire electrode was used as counter electrode in the cyclic voltamety and differential pulse voltametry studies. A linear relationship between anodic peak current and curcumin concentration was observed between 0.325 μM to 1.95μM at EPPG electrode with differential pulse voltammetry. Detection limit was calculated as 0,296 μM and the method successfully applied for detection of curcumin amount in a turmeric sample.

A novel and sensitive hexadecyltrimethylammoniumbromide functionalized Fe decorated MWCNTs modified carbon paste electrode for the selective determination of Quercetin

The fabrication of differential pulse voltametry (DPV) sensor for the effective detection of Quercetin (QR) was achieved by modifying carbon paste electrode (CPE) with Iron decorated multi walled carbon nano tubes (Fe-MWCNTs) followed by drop casting of hexadecyltrimethylammonium bromide onto the surface for optimal results. Cyclic voltammetry and DPV techniques were used for qualitative and quantitative analysis of QR (Quercetin) respectively. The sensor revealed impressive electro-catalytic behavior towards oxidation of QR with almost 6.4 times increase in current compared to bare carbon paste electrode CPE and also decrease in the energetics. Under optimum conditions, a wide linear dynamic range of 0.06 to 3000μM, with a lower limit of detection, 1.20nM with S/N=3 was observed. Absence of peak for the interfering molecules such as Folic acid and Ascorbic acid makes it a unique sensor with significant analytical advantage. The quantification of QR at this sensor was not affected by the presence of 1000 fold Uric Acid implying that the sensor is capable of specifically identifying QR in a mixture of interfering molecules. In this paper, we demonstrate that with minimal use of modifiers and simple procedures of fabrication, the fabricated sensor exhibits excellent stability, reproducibility and swift responses. Application of the developed electrode was demonstrated by detecting QR in wine and coconut water samples with satisfactory recoveries.

Synthesis of Well-Dispersed Silver Nanoparticles on Polypyrrole/Reduced Graphene Oxide Nanocomposite for Simultaneous Detection of Toxic Hydrazine and Nitrite in Water Sources

The AgNPs@PPy/rGO composites were synthesized by interfacial polymerization method using organic solvent dispersion of pyrrole as a reducing agent for graphene oxide. Aqueous solution of silver nitrate was used as a precursor for Ag nanoparticles and oxidizing agent to initiate polymerization reaction at the interface. The nanocomposite film electrode was employed for the electrochemical oxidation of inorganic pollutants namely hydrazine and nitrite and their oxidation potential was observed at +0.53 and +0.76 V (vs. Ag/AgCl), respectively in phosphate buffer. The kinetic parameters such as diffusion coefficient (1.67 × 10−5 and 3.9 × 10−5 cm2/s) and electron transfer rate constant (3.03 × 106 and 8.36 × 105 M−1s−1) of hydrazine and nitrite were measured by chronoamperometric method. Differential pulse voltametry was employed to determine individual as well as simultaneous detection of both analytes with well-resolved peak potential window (∼470 mV). The linear dynamics range from 0.6 μM to 6.6 μM and the detection limit of 19 and 21 nM for hydrazine and nitrite respectively were observed. In addition, the proposed sensor shows an enhanced stability and found to be incentive to select pollutants and biomolecules.

Simultaneous Detection of Ascorbic Acid, Dopamine and Uric Acid Using Carboxyl-C60 Modified Electrodes

In this paper, a gold electrode is modified with Carboxyl-C60 for the selective detection of dopamine (DA) in the presence of high concentration ascorbic acid (UA). And we also investigated the effects of electrical and catalytic mechanism of the modified electrodes. The electrochemical behavior of the carboxyl-C60 modified electrode was characterized by cyclic voltammetry (CV) and differential pulse voltametry (DPV), which showed good performance toward individual detection of DA and UA and even their simultaneous detection in the presence of 5.0 μM UA.

A novel sensing platform based on ionic liquid integrated carboxylic-functionalized graphene oxide nanosheets for honokiol determination

A novel ionic liquid, 4-hydroxy-1-methyl-[1-(3-pyrrolyl-propyl)]-piperidinium bromide, was synthesized and characterized. Carboxylic-functionalized graphene oxide nanosheets were modified with this ionic liquid to fabricate a nanocomposite which was denoted as GrO-COO-IL. Characterizations of FTIR, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy confirmed the successful conjunction of these two components. GrO-COO-IL nanocomposites were homogeneously dispersed with utralpure water, and were then coated onto glassy carbon electrode surface. Followed by cyclic voltammetric scanning, a graphene oxide-polymerized ionic liquid film modified electrode (GrO-COO-Poly-IL/GCE) was prepared, and was studied with electrochemical impedance spectroscopy and scanning electron microscope. It was found that both honokiol and magnolol exhibit sensitive voltammetric response at the GrO-COO-Poly-IL/GCE. Simultaneous assay of honokiol and magnolol was realized with differential pulse voltametry. In the presence of magnolol, the oxidation peak current was linearly related to honokiol concentration in the range of 1.0×10−8 ∼ 1.0×10−5molL−1 with a detection limit of 1.53×10−9molL−1 (S/N=3). Meanwhile, in the presence of honokiol, a linear relationship between the oxidation peak current and magnolol concentration was found from 7.0×10−8 to 1.0×10−5molL−1. The detection limit is calculated to be 8.27×10 −9molL−1 (S/N=3). In addition, GrO-COO-Poly-IL/GCE was successfully used for determination of honokiol in the traditional Chinese medicine, and was demonstrated to be an effective and sensitive method.

Highly sensitive electrochemical biosensor for glucose, DNA and protein using gold-polyaniline nanocomposites as a common matrix

In this paper, fabrication of a biosensing platform by covalent attachment of biomolecules on PAni nanowire (NW) decorated with gold nanoparticles (AuNP) has been reported. Efficiency of the platform has been evaluated after attachment of three different biomolecules viz. glucose oxidase (GOx), a single stranded DNA (ssDNA) and Lamin A antibody (LAA) for sensing of glucose, complementary DNA strand and Lamin A protein, respectively. Method of immobilization as well as method of detection was somewhat different for different systems. GOx and LAA were attached via NH2 functionalizations on AuNP while thiol-ended ssDNA was directly attached to AuNP surface. Sensing of glucose was monitored via chronoamperometry and the flow cell techniques while DNA detection was carried out via Differential Pulse Voltametry (DPV) and protein detection employing Electrochemical Impedance Spectroscopic (EIS) technique. Fabrication of the electrode was easy, enzymatic activity was well and reproducibility of the sensing process was good enough for sensing of glucose. The lower detection limit (1μM), higher sensitivity (14.63μAmM−1cm−2), greater stability and the excellent specificity indicated excellence of glucose sensor. For DNA sensor, detection of non complementary and complementary strands, even single base mismatch could be well discriminated up to the analyte concentration as low as 1μM. The similar detection limit was also obtained for detection of protein all which proves the suitability of the Au-PAni nanocomposites as a general sensor platform.

English

The preparation and electrochemical behavior of a carbon-paste electrode modified with an oxovanadium (IV) Schiff-base complex was studied. The modified electrode showed efficient catalysis in the electrochemical oxidation of methimazole (MMZ), an anti-hyperthyroid drug. The catalytic effect was observed for VIII oxidation peak which was produced via disproportionation of VIV in acidic solution. The diffusion coefficient (D) of MMZ and the rate constant of catalytic reaction (k) were estimated by chronoamperometry. Determination of MMZ was carried out using differential pulse voltametry. A linear dynamic range of 9 × 10–7 to 1 × 10-4 M with a detection limit of 8 × 10-7 M and a limit of quantitation of 2.6 × 10–6 M was resulted for the drug. The relative standard deviation for determination of 20 μM of the drug was found to be 1.7%. The method was used for the quantitation of MMZ in pharmaceutical formulations successfully.   Key words: Methimazole, determination, tablets, modified-carbon paste electrode.

An Electrochemical DNA Microbiosensor Based on Succinimide-Modified Acrylic Microspheres

An electrochemical microbiosensor for DNA has been fabricated based on new acrylic microspheres modified with reactive N-acryloxysuccinimide (NAS) functional groups. Hydrophobic poly(n-butylacrylate-N-acryloxysuccinimide) microspheres were synthesized in an emulsion form with a simple one-step photopolymerization technique. Aminated DNA probe was attached to the succinimde functional group of the acrylic microspheres via covalent bonding. The hybridization of the immobilized DNA probe with the complementary DNA was studied by differential pulse voltametry using anthraquninone-2-sulfonic acid monohydrate sodium salt (AQMS) as the electroactive hybridization label. The influences of many factors such as duration of DNA probe immobilization and hybridization, pH, type of ions, buffer concentrations, ionic strength, operational temperature and non-complementary DNA on the biosensor performance were evaluated. Under optimized conditions, the DNA microbiosensor demonstrated a linear response range to target DNA over a wide concentration range of 1.0 × 10−16 and 1.0 × 10−8 M with a lower limit of detection (LOD) of 9.46 × 10−17 M (R2 = 0.97). This DNA microbiosensor showed good reproducibility with 2.84% RSD (relative standard deviation) (n = 3). Application of the NAS-modified acrylic microspheres in the construction of DNA microbiosensor had improved the overall analytical performance of the resultant DNA microbiosensor when compared with other reported DNA biosensors using other nano-materials for membranes and microspheres as DNA immobilization matrices.

Investigation of polyelectrolyte for electrochemical detection of uric acid in presence of ascorbic acid

Uric acid (UA) was detected in the presence of ascorbic acid (AA) at GC electrode by cyclic voltametry (CV) and differential pulse voltametry (DPV) in aqueous media of cationic polyelectrolyte (poly(diallyldimethylammonium chloride) (PDDA)). Both, UA and AA are anionic nature and electro-static attraction with cationic solution. This lowered their oxidation potentials and increased anodic current. In CV studies, the UA oxidation potential was decreased by 400mV in the presence of PDDA along with increase in peak current. Effect of PDDA and pH on Epa and Ipa were also studied. About 360mV difference in oxidation peak potentials was observed for AA and UA in PDDA media, which established a quick method for their simultaneous determination. The detection limit of UA in the presence of 200 folds AA was found as 1μM with correlation coefficient of 0.994 and sensitivity of 0.05μAμM−1. The proposed method has been also applied for determining the UA in human urine without any pretreatment, and found to be satisfactory.

Selective determination of chloramphenicol at trace level in milk samples by the electrode modified with molecularly imprinted polymer

A novel voltammetric sensor for determination of chloramphenicol (CAP) in milk samples was introduced. The CAP selective molecularly imprinted polymer (MIP) and non imprinted polymer (NIP) were synthesized and then added to the carbon paste (CP) electrode composition in order to prepare MIP-CP electrode. The MIP, embedded in the carbon paste electrode, acted as the selective recognition element and pre-concentrator agent for CAP. CAP was extracted in the electrode for a definite time and then it was analyzed by differential pulse voltametry, found to be an effective determination method. The MIP-CP showed very high CAP recognition ability, compared to NIP-CP. The electrode washing, after CAP extraction, led to an enhanced selectivity. Various factors, known to affect the response behavior of the electrode, were investigated and optimized. This sensor showed a linear response range of 8.0×10−9−1.0×10−6M and lower detection limit of 2.0×10−9M (S/N=3). The sensor was successfully applied to the determination of CAP in milk samples.

Enhanced sensing of dopamine in the present of ascorbic acid based on graphene/poly(p-aminobenzoic acid) composite film

Graphene/p-aminobenzoic acid composite film modified glassy carbon electrode (Gr/p-ABA/GCE) was first employed for the sensitive determination of dopamine (DA). The electrochemical behavior of DA at the modified electrode was investigated by cyclic voltametry (CV), differential pulse voltametry (DPV) and amperometric curve. The oxidation peak currents of DA increased dramatically at Gr/p-ABA/GCE. The modified electrode was used to electrochemically detect dopamine (DA) in the presence of ascorbic acid (AA). The Gr/p-ABA composite film showed excellent electrocatalytic activity for the oxidation of DA in phosphate buffer solution (pH 6.5). The peak separation between DA and AA was large up to 220 mV. Using DPV technique, the calibration curve for DA determination was obtained in the range of 0.05-10 μM. The detection limit for DA was 20 nM. AA did not interfere with the determination of DA because of the very distinct attractive interaction between DA cations and the negatively Gr/p-ABA composite film. The proposed method exhibited good stability and reproducibility.

N-(Ferrocenylmethyl)-N-methylaminocyclotriphosphazenes

The reactions of N-(ferrocenylmethyl)-N-methylamine, C(5)H(5)FeC(5)H(4)CH(2)(Me)NH, with hexachlorocyclotriphosphazene, N(3)P(3)Cl(6), led to the formation of the N-(ferrocenylmethyl)-N-methylaminocyclotriphosphazene derivatives, N(3)(-)P(3)Cl(6-n)[N(Me)CH(2)C(5)H(4)FeC(5)H(5)](n) (n = 1-3). Only small amounts of higher degrees of substitution could be detected. In the case of the disubstituted products, the ratio of isomers was dependent on the polarity of the solvent. In nonpolar solvents the ratio was trans > geminal > cis while in acetonitrile only equal amounts of trans and cis isomers were observed. The reaction of N-(ferrocenylmethyl)-N-methylamine with (methacryloylbutenedioxy)pentachlorocyclotriphosphazene, N(3)P(3)Cl(5)O(CH(2))(4)OC(O)C(Me)=CH(2), gives the surprising geminal isomer 2,2-N(3)P(3)Cl(4)[O(CH(2))(4)OC(O)C(Me)=CH(2)]N(Me)CH(2)C(5)H(4)FeC(5)H(5) and the tris derivative 2,2',4-N(3)P(3)Cl(3)[O(CH(2))(4)OC(O)C(Me)=CH(2)][N(Me)CH(2)C(5)H(4)FeC(5)H(5)](2). All of the phosphazene derivatives were characterized by elemental analyses, mass spectrometry, IR and NMR ((1)H, (13)C, (31)P) spectroscopy, and electrochemical techniques (cyclic, normal pulse, and differential pulse voltametry). The compounds all undergo a single, reversible oxidation reduction process.

A PC-controlled voltage pulse generator for electroanalytical applications

We present the design of a voltage pulse generator controlled by an IBM or compatible AT Personal Computer (PC) capable of synthesizing some of the voltage pulse wave forms commonly used in electrochemical studies. The included signals are: differential pulse voltametry, differential normal pulse voltametry, and differential pulse amperometry. Additionally, a triangular wave form and a constant-voltage signal, used in the pretreatment of carbon fiber microelectrodes for neurochemical analysis, are also available. Operating the generator imposes a minimum of restrictions on the specification of the duration, amplitude, and type of wave shapes. Low-cost PC-based design allows for compatibility, portability, and versatility. The operating ranges of the wave form parameters for the three voltametric signals are: initial voltage, −0.9–+0.9 V; step amplitude, 0.1–900 mV; period, 6 ms–60 s; measuring pulse amplitude, 0.1–900 mV; measuring pulse duration, 2 ms–20 s; prepulse duration, 2 ms–20 s. In the electrode pretreatment mode, the operating ranges are: amplitude, 0–±5 V; duration, unlimited; frequency, 15–240 Hz. The generator uses its own time base for the generation of all signals, thereby rendering it independent of processor clock speed or power-line frequency. The results of the experimental evaluation indicate that the system is accurate within ±10% of the expected values, taking into account the errors associated with the signal synthesis and the digitizing process. The maximum achievable scan rate is 500 V/s, and the highest frequency for the triangular wave form is 240 Hz. Therefore, the pulse generator could be used for fast cyclic voltametry (FCV). FCV and other wave forms could be added through software modules, without any hardware changes. We conclude that the PC-based electrochemistry pulse generator represents an economical and flexible alternative for electroanalytical applications.