Catalytic Hydrogen Wave Research Articles

Determination of Manganese(II) using Catalytic Hydrogen Wave (CHW) Technique in Environmental and Biological Samples

Background: A simple, low cost and highly sensitive catalytic hydrogen wave (CHW) method has developed for the investigation of Manganese(II) in ammonium 4-phenylpiperazine-1- dithiocarbamate and ammonium 4-benzylpiperidine-1-dithiocarbamate in various environmental and biological samples using D.C. polarography. This procedure was based on the reaction of Mn(II) in APP-DTC/ABP-DTC in the presences of NH4Cl-NH4OH medium at pH 6.6 and 7.2 respectively. The resulting oxidation signals were obtained at -0.78 V and -0.64 V vs SCE, owing to the CHWs. Different experimental conditions such as pH effects, background electrolyte (NH4Cl-NH4OH) effects and DTCs and Mn(II) ion effects have been studied. The current method was effectively employed for the testing of Mn(II) in different environmental and biological samples and attained recovery percentages (95-99%) are comparable to the Atomic Absorption Spectrophotometry (AAS) method. Methods: Direct current polarography, model CL-357 and CL-25 (Elico Private Ltd, Hyderabad, India), Shimadzu AA 6300 spectrometer furnished thru a deuterium background corrector and hollow cathode lamp, at corresponding wavelengths (resonance line) with an air acetylene flame. The experimental guidelines remained those suggested by the makers. Results: The effect of NH4Cl between 0.1 to 0.7 M on the nature of CHW at DME, maintaining the concentrations of Mn(II) at 4.0 ppm and DTC at 3.0 mM (APP-DTC/ABP-DTC) then adjusting the pH to 6.6/7.2 (APP-DTC/ABP-DTC). The polarograms were well-defined in NH4Cl of 0.4/0.5 M for APP-DTC/ABP-DTC. The peak height decreased beyond this concentration and therefore 0.4/0.5 M (APP-DTC/ABP-DTC) concentrations was kept for more analysis. At fixed concentration of DTC, (3.0 mM APP-DTC/ABP-DTC) and (0.4/0.5 M for APP-DTC/ ABP-DTC) NH4Cl adjusting the pH to 6.6/7.2 respectively the metal ion concentration of the Mn(II) was adjusted between 0.05 to 7.0 ppm and results of CHWs were studied. The peak current increased linearly with Mn(II) concentration in the range 0.05 to 4.0 ppm for both DTCs. However, the sensitivity of the method was more with APP-DTC/ABP-DTC because of strong complex of Mn(II) and increased catalytic activity. Conclusion: The developed CHW method is highly sensitive, simple and spontaneous for the analysis of Mn(II) in environmental and biological samples. The polarographic reduction of Mn(II) in aqueous solutions in the attendance of DTC displays a catalytic wave as a role of pH, concentration of supporting electrolyte and metal ion. The graphs of catalytic signals as a role of the concentration of dithiocarbamate shows that the signals do not vary linearly with the concentration of dithiocarbamate which the characteristic of Brdicka CHWs. It is presumed that the dithiocarbamate complexes with metal ions involve adsorption process and can be described by a Langmuir adsorption isotherm and the plot of CL/ip Vs CL should be linear. The CHW method is free from interference effect avoiding the removal stages which made towards placing among utmost sensitive methods for the analysis of Mn(II) in different Environmental and Biological samples.

Detection of Phosphate in Human Blood Based on a Catalytic Hydrogen Wave at a Molybdenum Phosphide Modified Electrode.

Detection of inorganic phosphate is very important in environmental and health care applications. In this work, we found that phenomenon similar to "catalytic hydrogen wave" occurred on a molybdenum phosphide (MoP) modified electrode in the presence of phosphate, that is, a new wave of catalytic hydrogen evolution appeared before the normal hydrogen evolution reaction. The catalytic hydrogen wave arose from a structure similar to phosphomolybdic acid (noted as MoPO), which was formed by the interaction between phosphate and molybdenum oxides on the surface of the MoP modified electrode, resulting in the altered surface structure and adjusted interface catalytic activity. A novel phosphate electrochemical sensor was constructed based on this phenomenon with a linear range from 0.10 to 20.0 mmol·L-1, an actually determined minimum concentration of 0.030 mmol·L-1, and recoveries of 94%-107%, and this sensor was successfully applied to the detection of phosphate in human blood. Furthermore, this work proposes a new sensing method based on catalytic hydrogen waves on the modified electrodes.

Dithiocarbamate Induced Catalytic Hydrogen Wave for the determination of Iron (II) in Waters and Leafy Vegetables: Experimental and Computational Approach

Dithiocarbamate Induced Catalytic Hydrogen Wave for the determination of Iron (II) in Waters and Leafy Vegetables: Experimental and Computational Approach

Sensitive Determination of Nickel (II) using Catalytic Hydrogen Wave in the Presence of Dithiocarbamates at DME

Two new ligands, ammonium 2,6-dimethylmorpholine dithiocarbamate and ammonium 3-methylpiperidine dithiocarbamate were synthesized for the determination of nickel (II) in various environmental samples. The method was based on chelation of nickel (II) with ADMM-DTC/AMP-DTC in presence of NH4OH at pH 6.4 to produce catalytic hydrogen currents at -1.30V and -1.41 V vs SCE respectively and prior detected by DC polarography at Dropping Mercury Electrode (DME). Optimized polarographic conditions were established by studying effect of pH, supporting electrolyte, ligand and metal ion concentrations and effect of adverse ions on peak height to improve the sensitivity, selectivity and detection limits of the present method. The present technique was successfully applied for the analysis of nickel (II) in different matrices with recoveries ranging from 97.00 - 99.00% and the results obtained were comparable with the differential pulse polarography.

Sensitive Determination of Nickel (II) using Catalytic Hydrogen Wave in the Presence of Dithiocarbamates at DME

Sensitive Determination of Nickel (II) using Catalytic Hydrogen Wave in the Presence of Dithiocarbamates at DME

Polarographic Interaction of Nickel (II) with Ammonium Piperidine-1-Carbodithioate: Application to Environmental Samples

This paper describes the interaction of nickel (II) with ammonium piperidine-1-carbodithioate (APC) using Direct Current (DC) polarography (DCP) & differential pulse polarography (DPP) at the Dropping Mercury Electrode (DME) in NH4Cl-NH4OH buffer medium at pH 6.0. The polarograms shows a predominant peak for nickel (II)-APC at -1.30 V vs SCE, indicating the production of catalytic hydrogen wave (CHW) due to electrostatic interactions between APC and nickel (II). The interactions were characterized with UV-visible spectrophotometer, FT-IR and cyclic voltammetric techniques. The developed method was applied successfully to determine the nickel (II) levels in leafy vegetables and biological samples with acceptable recoveries.

Multivariate optimization of differential pulse polarographic–catalytic hydrogen wave technique for the determination of nickel(II) in real samples

Multivariate optimized experimental conditions were established for the determination of nickel(II) in 92 grape samples after complexation with ammonium piperidine dithiocarbamate (APDC) and ammonium morpholine dithiocarbamate (AMDC). Differential pulse polarographic (DPP) studies of the wave characteristics indicated that it is of the catalytic hydrogen wave (CHW) type sensitive to pH, concentration and scan rates. A single, sharp peak obtained at −1.22V allowed for the trace determination of nickel(II) in the range of 3.2×10−6 to 1.17×10−3M with a linear calibration and a detection limit of 1.8×10−6 and 2.7×10−6M for APDC and AMDC respectively. Mechanistic aspects between APDC/AMDC and nickel(II) were confirmed with cyclic voltammetry and supported by theoretical calculations. The DFT calculations of piperidine adduct reveal a smaller HOMO–LUMO energy gap than morpholine adduct, suggesting that piperidine adduct has a greater tendency to act as an electron donor.

Square-wave adsorptive stripping voltammetric determination of antihypertensive agent telmisartan in tablets and its application to human plasma

The adsorptive stripping voltammetry of telmisartan was investigated with a hanging mercury drop electrode. This compound produced a catalytic hydrogen wave at -1.5 V in Britton Robinson buffer of pH 10.38, and the peak current increased with adsorptive accumulation at the electrode. Adsorptive stripping voltammetry with the catalytic hydrogen wave could provide a sensitive novel method for the determination of telmisartan. Various chemical and instrumental parameters affecting the monitored electroanalytical response were investigated and optimized for telmisartan determination. Under these optimized conditions the squarewave adsorptive stripping voltammetric ( SWAdSV ) peak current showed a linear dependence on drug concentration over the range 0.05-3.00 µg/mL (1 × 10 -7 ⎯6 × 10 -6 M) (r = 0.999) with accumulation for 120 s at -1.0 V vs. Ag/AgCl. The proposed electrochemical procedure was successfully applied for the determination of telmisartan in pharmaceutical tablets and human plasma. The results of the developed SW� AdSV method were comparable with those obtained by reported analytical procedures.

Polarographic Catalytic Hydrogen Wave Technique for the Determination of Copper(II) in Leafy Vegetables and Biological Samples

Polarographic Catalytic Hydrogen Wave Technique for the Determination of Copper(II) in Leafy Vegetables and Biological Samples

A new and very simple procedure for the differential pulse polarographic determination of ultra trace quantities of tungsten using catalytic hydrogen wave and application to tobacco sample

In this work a new and very simple differential pulse polarographic method is established for the trace determination of tungsten using catalytic hydrogen peak. For its determination, polarograms have been taken in various electrolytes including Britton–Robinson buffer (pH=2.0, pH=4.0, pH=5.0 and pH=6.0), nitric acid, hydrochloric acid, perchloric acid and phosphoric acid. The highest peak was obtained in the presence of 0.01M H3PO4 +0.1M KCl (pH=2.0–2.5) which appeared at −1.1V. The effects of pH, phosphate concentration, type of electrolyte on this peak have been studied. The height of the hydrogen catalytic peak was increasing with the addition of Mo(VI). Formation of a heteropoly acid was responsible of the catalytic hydrogen peak. The best condition for the determination of 5×10−8MW(VI) was found to be 1×10−5M Mo(VI) and 1×10−2M H3PO4+0.1M KCl (pH=2.0–2.5).The interference effect of Cu(II), Pb(II), Sn(IV), Mo(VI), Se(IV), As(III) and Zn(II) have also been studied. Among these ions only in the presence of As(III), the catalytic hydrogen peak of tungsten (shown as Mo–W) overlapped with the hydrogen catalytic peak of arsenic (Mo–As). This interference could be eliminated by oxidizing As(III) into As(V) using HNO3. With the newly established method the limit of detection (LOD) was 1.3×10−9M (S/N=3). This method was applied successfully for the determination of tungsten in digested tobacco sample.

Voltammetric Method for Manganese Analysis in Indian Traditional Leafy Vegetables and Medicinal Plants Collected Around Tirupati Town, a Famous Pilgrim Center in India: The Catalytic Hydrogen Wave (CHW) Technique

Cost-effective, rapid, sensitive, and novel catalytic hydrogen wave technique (CHW) was developed for the analysis of manganese(II) in NH4Cl–NH4OH medium at pH 6.2 and produced catalytic hydrogen waves at −0.60 and −0.56 V Vs SCE with ammonium piperidine dithiocarbamate and ammonium morpholine dithiocarbamate, respectively, in various leafy vegetables and medicinal plants collected around Tirupati, Chittoor District, Andhra Pradesh which is one the famous pilgrim centers in India. Different optimal parameters like effect of pH, supporting electrolyte (NH4Cl–NH4OH) concentration, ligand and metal ion concentrations, and effect of adverse ions on peak height were studied to improve the sensitivity, selectivity, and detection limits CHW technique. This technique was compared in terms of Student t test and variance ratio f test with differential pulse polarography (DPP) method. The technique was applied for the analysis of manganese(II) in leafy vegetables and medicinal plants. The results obtained are in good agreement with DPP.

Electrochemical behavior of Moclobemide at mercury and glassy carbon electrodes and voltammetric methods for its determination

Electrochemical oxidation and reduction properties of Moclobemide (MCB) were investigated at glassy carbon electrode (GCE) and hanging mercury drop electrode (HMDE). Diffusion-adsorption behavior and some extra electrochemical parameters such as diffusion coefficient, number of transferred electrons and proton participated to its electrode mechanisms on both electrode and surface coverage coefficient were calculated from the results of cyclic voltammetry and square-wave voltammetry. Reversible catalytic hydrogen wave mechanism was proposed at HMDE and single two-electron/two-proton irreversible oxidation mechanism controlled by adsorption with some diffusion contribution at GCE was proposed. Experimental parameters were optimized to develop new, accurate, rapid, selective and simple voltammetric methods for direct determination of MCB in pharmaceutical dosage forms and spiked human serum samples without time-consuming steps prior to drug assay. In these methods, the lowest limit of detection (LLOD) was found to be 0.0235 μM. Methods were successfully applied to determine the MCB content of commercial pharmaceutical preparations and spiked human urine. The methods were found to be highly accurate and precise.

Dithiocarbamates as a Sensitive Electroanalytical Reagent: Determination of Chromium by Catalytic Hydrogen Wave at DME in Water Systems and Vegetables

Simple, sensitive catalytic hydrogen polarographic method was developed for the determination of chromium (VI) with ammonium piperidine dithiocarbamate (Amm Pip-DTC) and ammonium morpholine dithiocarbamate (Amm Mor-DTC) in various water systems and vegetables. The method was based on the catalytic hydrogen wave of Amm Pip-DTC-Cr(VI) and Amm Mor-DTC-Cr(VI) complexes in the presence of NH4Cl–NH4OH medium at pH 7.5 and 9.6 and produce a catalytic hydrogen waves at −1.59 and −1.65 V Vs SCE, respectively. Various optimum parameters such as effect of pH, NH4Cl–NH4OH, Pip-DTC, metal ion concentrations and excipient effect on peak height were investigated to enhance the sensitivity, selectivity, and detection limits of the present method and compared in terms of Students t test and variance ratio f test with differential pulse polarography (DPP) method. The proposed method was applied for the determination of chromium (VI) in various water system and vegetables and the results obtained were in good agreement with DPP.

Voltammetry of resazurin at a mercury electrode

AbstractElectrochemical behavior of resazurin on HMDE in Britton-Robinson (B-R) buffers (pH 2.0–10.0) was studied using the square-wave voltammetry (SWV), square-wave adsorptive stripping voltammetry (SWAdSV), and cyclic voltammetry (CV) techniques. The voltammogram of resazurin in B-R buffer at pH < 4.0 exhibited two cathodic reduction peaks. The voltammetric peaks were obtained at −0.144 V (reversible) and −1.250 V (irreversible) at pH 3.2, and correspond to the reduction of resorufin to dihydroresorufin and to the catalytic hydrogen wave, respectively. At pH > 4.0, a new irreversible cathodic reduction peak, assigned to the protonation of N-oxide on the phenoxazin ring, was observed. Electrochemical parameters (I p/E p, I p/v, I p/pH, I p/t acc) of the compound were determined. From the voltammetric data, electrochemical reduction mechanisms for all peaks have been suggested. Maximum peak current for the reversible peak was obtained at pH 4.1. A linear relationship between the current and concentration was determined, and also the lowest detection limit was found as 3.25 × 10−8 mol L−1 and 1.98 × 10−10 mol L−1 for SWV and SWAdSV, respectively.

Cathodic Stripping Voltammetric Determination of Tellurium(IV) with in situ Plated Bismuth-Film Electrode

A very sensitive and reliable method is proposed for the determination of tellurium(IV) [Te(IV)] by Osteryoung square-wave cathodic stripping voltammetry. This method is based on the reduction of Te(IV) with bismuth(III) onto an edge-plane pyrolytic graphite electrode, followed by a cathodic potential scan. The reduced Te gave a well-defined catalytic hydrogen wave at −1200 mV vs. Ag/AgCl. The peak height of the catalytic wave was directly proportional to the initial Te(IV) concentration in the concentration ranges of 0.01–0.10 and 0.1–1.0 µg L−1 with 30 s deposition time. A 3σ detection limit of 1.0 ng L−1 Te(IV) was obtained with the same deposition time. The relative standard deviation was 3% on replicate runs (n = 5) for the determination of 0.1 µg L−1 Te(IV). Analytical results of natural water samples demonstrate that the proposed method is applicable to the determination of traces of Te(IV).

Sensitive determination of chromium by the catalytic hydrogen wave in the presence of thiocompounds at DME

A sensitive polarographic method for the determination of chromium is proposed, based on the catalytic hydrogen wave of Cr VI -xanthate complexes in the presence of NH 4 Cl at mercury electrode. The Cr VI -xanthate complexes produce a catalytic hydrogen wave at -1.52 V vs SCE with potassium propyl xanthate (Kpxan) and at -1.47 V vs SCE with potassium cyclohexyl xanthate (Kchxan) in NH 4 Cl-NH 4 OH medium (pH 9.6 for Kpxan and 9.2 for Kchxan). The peak height is proportional to metal ion concentration. The proposed method is free of interference from other metal ions except Mo VI and is evaluated to micro level Cr VI down to 0.1 ppm by the determination of chromium content in drinking water samples, industrial effluents, tannery waste water and agricultural materials.

Voltammetric reduction of finasteride at mercury electrode and its determination in tablets

Finasteride in hydroalcoholic solutions (ethanol/Britton-Robinson buffer, 30/70) exhibits cathodic response in a wide range of pH (−0.5 to 12) using differential pulse (DPP) and tast polarography (TP). The reduction peak of finasteride at acidic pH, is a catalytic proton peak resulting from a mechanism involving a first protonation of finasteride followed by the reduction of the protons combined with finasteride in order to regenerate finasteride and liberate hydrogen. Based on the catalytic hydrogen wave, a novel method for the determination of finasteride can be proposed. For analytical purposes we selected DPP technique in an ethanol/0.0625 mol L −1 H 2SO 4 (30/70) solution medium. In this condition the I p varied linearly with finasteride concentration between 5 × 10 −5 and 5 × 10 −4 mol L −1. Within-day and inter-day reproducibility's were adequate with R.S.D. values lower than 2%. The selectivity of the method was checked with both accelerated degradation trials and typical excipients formulations. The developed method was applied to the assay and the uniformity content of finasteride tablets and compared with the standard HPLC method. The DPP-developed method was adequate for the finasteride determination in pharmaceutical forms as that exhibited an adequate accuracy, reproducibility and selectivity. Furthermore, treatment of the sample was not required as in HPLC; the method is not time-consuming and less expensive than the HPLC ones.

Determination of Selenium(IV) by Catalytic Stripping Voltammetry with an in situ Plated Bismuth-film Electrode

A very sensitive and simple method is presented for the determination of Se(IV) by Osteryang square-wave cathodic stripping voltammery (OSWCSV). The method is based on the reduction of Se(IV) with Bi(III) onto an edge-plane type of pyrolytic graphite substrate, followed by a cathodic potential scan. OSWCSV studies indicate that the reduced selenium produced a distinct catalytic hydrogen wave at -1150 mV vs. Ag/AgCl. The peak height of the catalytic hydrogen wave was directly proportional to the initial Se(IV) concentration in the ranges of 0.1 - 1.0 and 1.0 - 20.0 microg L(-1) (correlation coefficients 0.9800 and 0.9901, respectively) when the optimized parameters were used. A 3sigma detection limit of 0.025 microg L(-1)0 Se(IV) was obtained at 30 s deposition time. The relative standard deviation was 4.0% on replicate runs (n = 12) for the determinations of 0.10 microg L(-1) Se(IV). Analytical results of natural water samples demonstrate that the proposed method is applicable to speciation analysis of Se(IV) and Se(VI).

Cathodic stripping voltammetric determination of As(III) with in situ plated bismuth-film electrode using the catalytic hydrogen wave

A highly sensitive method has been developed for the determination of trace As(III) by a square wave cathodic stripping voltammetry employing in situ plated bismuth-film on edge-plane graphite substrate as working electrode. The presence of As(III) enhanced a cathodic peak corresponding to the catalytic hydrogen wave due to Se(IV) at about −1150 mV. Linear calibration curves for As(III) determination were obtained over the concentration ranges of 0.01–1.0 μg L −1 and 1.0–12.0 μg L −1 at deposition times of 30 s and 10 s, respectively. The detection limit (3 σ) was estimated to be as low as 0.7 ng L −1 As(III) at 30 s deposition time. The optimum experimental parameters and probable interference from foreign ions and organic compounds were investigated. This proposed method could be applied to analyses of certified reference material, synthetic and natural water samples.

Differential pulse polarographic determination of trace quantities of arsenic using catalytic hydrogen wave and its application

Abstract In the presence of Molybdenum(VI) and Arsenic(III) a new polarographic peak appears at about −1.2 V which corresponds to a hydrogen catalytic wave. It allows trace determination of both ions in the range of 10 −6 −10 −8 M with a detection limit of 2 × 10 −9 M. The optimum working condition was found to be as 0.1 M acetate buffer and pH 3.0. For the determination of one of these ions, the second ion concentration has to be about 500 times higher than the other ion under investigation. There is no serious interference from some cations such as Cr(III), Zn(II), Pb(II), Cd(II), Ni(II), Cu(II), Se(IV) and anions such as bromide, chloride, nitrate, sulfate and sulfite when present 1.0–100 times of arsenic. They did not interfere in the determination of arsenic. In the presence of these ions 10 −8 M arsenic could be determined with great accuracy. The arsenic content in beer has been determined using this method.