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Hanging Mercury Drop Electrode (hanging + mercury_drop_electrode)
Selected AbstractsFast Mapping of Gunshot Residues by Batch Injection Analysis with Anodic Stripping Voltammetry of Lead at the Hanging Mercury Drop ElectrodeELECTROANALYSIS, Issue 2 2005Adriana De, Donato Abstract The forensic analysis of lead in gunshot residues (GSR) sampled on the hands of potential shooters is rendered faster, simpler and less expensive by a new batch injection analysis (BIA) method, based on differential pulse anodic stripping voltammetry (DPASV). A simple "J" shaped adaptor was designed to direct the flux of the analyte injected with a micropipettor onto the hanging mercury drop electrode of any commercial electrode stand. Sampling methods for GSR were compared and lifting with adhesive tape was elected for field use. The tapes are glued on polyethylene screens and stored in capped vials. Sampling with multiple strips provides coarse mapping of the distribution of lead on the shooter's hands. After a dissolution/extraction step with chloroform/aqueous 0.10,mol,L,1 HCl, 100,,L of the aqueous phase are injected during 25,s for accumulation of lead on the HMDE at ,0.60,V (vs. Ag/AgCl). A detection limit of 20,ng/mL of Pb(II), outreaching for GSR analysis, is reached without oxygen removal, at a frequency of 20 injections per hour. Results for sequences of shootings with a revolver and a pistol are presented. [source] The Electrochemical Behavior of ,-Ketoglutarate at the Hanging Mercury Drop Electrode in Acidic Aqueous Solution and Its Practical Application in Environmental and Biological SamplesELECTROANALYSIS, Issue 12 2004Li Yang Abstract The voltammetric behavior of ,-ketoglutarate (,-KG) at the hanging mercury drop electrode (HMDE) has been investigated in acetate buffer solution. Under the optimum experimental conditions (pH,4.5, 0.2,M NaAc-HAc buffer solution), a sensitive reductive wave of ,-KG was obtained by linear scan voltammetry (LSV) and the peak potential was ,1.18,V (vs. SCE), which was an irreversible adsorption wave. The kinetic parameters of the electrode process were ,=0.3 and ks=0.72,1/s. There was a linear relationship between peak current ip, ,-KG and ,-KG concentration in the range of 2×10,6,8×10,4,M ,-KG. The detection limit was 8×10,7,M and the relative standard deviation was 2.0% (C,-KG=8×10,4,M, n=10). Applications of the reductive wave of ,-KG for practical analysis were addressed as follows: (1) It can be used for the quantitative analysis of ,-KG in biological samples and the results agree well with those obtained from the established ultraviolet spectrophotometric method. (2) Utilizing the complexing effect between ,-KG and aluminum, a linear relationship holds between the decrease of peak current of ,-KG ,ip and the added Al concentration C in the range of 5.0×10,6,2.5×10,4,M. The detection limit was 2.2×10,6,M and the relative standard deviation was 3.1% (C=4×10,5,M, n=10). It was successfully applied to the detection of aluminum in water and synthetic biological samples with satisfactory results, which were consistent with those of ICP-AES. (3) It was also applied to study the effect of AlIII on the glutamate dehydrogenase (GDH) activity in the catalytically reaction of ,-KG+NH+NADH,L -glutamate+NAD++H2O by differential pulse polarography (DPP) technique. By monitoring DPP reductive currents of NAD+ and ,-KG, an elementary important result was found that Al could greatly affect the activity of GDH. This study could be attributed to intrinsic understanding of the aluminum's toxicity in enzyme reaction processes. [source] Elimination Procedure as a Novel and Promising Mathematical Approach in Voltammetric MethodsELECTROANALYSIS, Issue 17-18 2010Nuria Serrano Abstract In the contribution, it has been demonstrated that Elimination Voltammetry with Linear Scan (EVLS) introduces an enhancement of the linear sweep and/or cyclic voltammetric results, and provides information about the type of the currents involved in the considered process. An extension of EVLS has been developed for any combination of scan rates (integers) for six elimination functions that are capable of conserving or eliminating of some voltammetric current components. Simple procedure to obtain the necessary coefficients from the chosen scan rates has been reported. In addition, the calculation and discussion of the relative error of elimination function (REEF) have been presented. The verification of the presented calculations has been done by studying different ratios of scan rates for reduction and oxidation processes of Cd(II) at a hanging mercury drop electrode (HMDE). [source] Cathodic Stripping Voltammetry of Uracil.ELECTROANALYSIS, Issue 1 2009Experimental, Theoretical Study Under Conditions of Square-Wave Voltammetry Abstract The electrode mechanism of uracil at a hanging mercury drop electrode (HMDE) is studied under cathodic stripping square-wave voltammetric mode owing to the cathodic dissolution of a sparingly soluble compound formed between the electrode material and uracil. The experimental results can be partly explained in the light of the recent theory for cathodic stripping processes of insoluble salts under conditions of square-wave voltammetry. It is established that the electrode reaction is complicated by attractive interactions between the deposited species of the insoluble compound. To elucidate the electrode mechanism completely a novel theoretical model is developed considering adsorption of the reacting analyte and lateral interactions between species of the insoluble compound. With the help of numerical simulations the effect of interactions is studied in detail, emphasizing the properties of the response that can be used as diagnostic criteria for recognition of the type of interaction forces. Theoretically predicted voltammetric properties agree well with the experimental results enabling clarification of the complex electrode mechanism of uracil at HMDE. [source] Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping VoltammetryELECTROANALYSIS, Issue 12 2008B. Gholivand Abstract A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N,-bis(salicylaldehydo)4-carboxyphenylenediamine (BSCPDA),complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02,mol L,1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42,,M, pH,9.6 and adsorption potential at ,50,mV versus Ag/AgCl. With an accumulation time of 20,s, the peaks current are proportional to the concentration of nickel and cadmium over the 1,180, and 0.5,200,ng mL,1 with detection limits of 0.06 and 0.03,ng mL,1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98,nA mL ng,1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results. [source] Highly Sensitive and Selective Measurement of Bismuth in Seawater and Drug with 1,2-Phenylenedioxydiacetic Acid by Cathodic Adsorptive Stripping VoltammetryELECTROANALYSIS, Issue 7 2006B. Gholivand Abstract A new method is presented for determination of bismuth based on cathodic adsorptive stripping of complex bismuth with 1,2-phenylenedioxydiacetic acid (PDA) at a hanging mercury drop electrode (HMDE). The effect of various parameters such as pH, concentration of ligand, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum conditions for determination of bismuth include nitric acid concentration 0.01,M, 8.0×10,4,M PDA and accumulation time 120,s, accumulation potential of ,200,mV. The limits of detection are 0.25 and 0.05,nM, and responses are linear 1,1000 and 0.1,400,nM at tacc of 60 and 120,s, respectively. Many common anions and cations do not interfere in the determination of bismuth. The method was applied to the determination of bismuth in some real samples such as sea , and spring water and drug. [source] Determination of Platinum with Thiosemicarbazide by Catalytic Adsorptive Stripping Voltammetry (AdSV)ELECTROANALYSIS, Issue 4 2005Sylwester Huszal Abstract This work describes a very sensitive and selective voltammetric procedure for the determination of platinum. Instead of commonly used hydrazine, thiosemicarbazide as a component of supporting electrolyte was applied. The method is based on adsorption of platinum-thiosemicarbazone complex, formed in situ in voltammetric cell from thiosemicarbazide and formaldehyde, coupled with a hydrogen catalytic reaction at a hanging mercury drop electrode. The linear relation between platinum concentration and height of analytical signal was observed up to 1.5×10,9,mol,L,1 with the detection limit calculated as 1.5×10,13,mol,L,1 (3,s of the blank) after 50,s of accumulation time. The effect of various interferences from other ions was studied. Described method was applied for platinum determination in hydroponically cultivated plants after microwave decomposition. [source] Fast Mapping of Gunshot Residues by Batch Injection Analysis with Anodic Stripping Voltammetry of Lead at the Hanging Mercury Drop ElectrodeELECTROANALYSIS, Issue 2 2005Adriana De, Donato Abstract The forensic analysis of lead in gunshot residues (GSR) sampled on the hands of potential shooters is rendered faster, simpler and less expensive by a new batch injection analysis (BIA) method, based on differential pulse anodic stripping voltammetry (DPASV). A simple "J" shaped adaptor was designed to direct the flux of the analyte injected with a micropipettor onto the hanging mercury drop electrode of any commercial electrode stand. Sampling methods for GSR were compared and lifting with adhesive tape was elected for field use. The tapes are glued on polyethylene screens and stored in capped vials. Sampling with multiple strips provides coarse mapping of the distribution of lead on the shooter's hands. After a dissolution/extraction step with chloroform/aqueous 0.10,mol,L,1 HCl, 100,,L of the aqueous phase are injected during 25,s for accumulation of lead on the HMDE at ,0.60,V (vs. Ag/AgCl). A detection limit of 20,ng/mL of Pb(II), outreaching for GSR analysis, is reached without oxygen removal, at a frequency of 20 injections per hour. Results for sequences of shootings with a revolver and a pistol are presented. [source] The Electrochemical Behavior of ,-Ketoglutarate at the Hanging Mercury Drop Electrode in Acidic Aqueous Solution and Its Practical Application in Environmental and Biological SamplesELECTROANALYSIS, Issue 12 2004Li Yang Abstract The voltammetric behavior of ,-ketoglutarate (,-KG) at the hanging mercury drop electrode (HMDE) has been investigated in acetate buffer solution. Under the optimum experimental conditions (pH,4.5, 0.2,M NaAc-HAc buffer solution), a sensitive reductive wave of ,-KG was obtained by linear scan voltammetry (LSV) and the peak potential was ,1.18,V (vs. SCE), which was an irreversible adsorption wave. The kinetic parameters of the electrode process were ,=0.3 and ks=0.72,1/s. There was a linear relationship between peak current ip, ,-KG and ,-KG concentration in the range of 2×10,6,8×10,4,M ,-KG. The detection limit was 8×10,7,M and the relative standard deviation was 2.0% (C,-KG=8×10,4,M, n=10). Applications of the reductive wave of ,-KG for practical analysis were addressed as follows: (1) It can be used for the quantitative analysis of ,-KG in biological samples and the results agree well with those obtained from the established ultraviolet spectrophotometric method. (2) Utilizing the complexing effect between ,-KG and aluminum, a linear relationship holds between the decrease of peak current of ,-KG ,ip and the added Al concentration C in the range of 5.0×10,6,2.5×10,4,M. The detection limit was 2.2×10,6,M and the relative standard deviation was 3.1% (C=4×10,5,M, n=10). It was successfully applied to the detection of aluminum in water and synthetic biological samples with satisfactory results, which were consistent with those of ICP-AES. (3) It was also applied to study the effect of AlIII on the glutamate dehydrogenase (GDH) activity in the catalytically reaction of ,-KG+NH+NADH,L -glutamate+NAD++H2O by differential pulse polarography (DPP) technique. By monitoring DPP reductive currents of NAD+ and ,-KG, an elementary important result was found that Al could greatly affect the activity of GDH. This study could be attributed to intrinsic understanding of the aluminum's toxicity in enzyme reaction processes. [source] Novel, Sensitive Voltammetric Methods for Titanium Determination Using Chromotropic Acid and Azo-Compounds as Complexing AgentsELECTROANALYSIS, Issue 12 2003Marcin Gawrys Abstract Voltammetric behavior of titanium(IV) complexes with chromotropic acid, its azo-derivatives: 2-(4-sulfophenylazo)-1,8-dihydroxy-3,6-naphthalenedisulfonic acid (SPANDS), chromotrope 2B, sulfonazo III and other azo-compounds: calmagite, tropeoline O and kalces was investigated at a hanging mercury drop electrode. These complexes strongly adsorb onto the electrode, thus can be determined by an adsorptive stripping voltammetry (optimal pH about 6). At pH about 3 reduction current enhancement for Ti-kalces complex was observed in the presence of chlorate ions. It is a rare example of a catalytic process with azo-compound as a complexing agent. Signal for Fe-calmagite complex reduction was also observed. Influence of foreign ions and the optimal conditions for titanium determination are described in detail. Additionally, a connection between obtained results and a structure of titanium complexes is discussed. [source] Voltammetric Determination of Free and Total Sulfur Dioxide in BeerELECTROANALYSIS, Issue 5-6 2003J. Almeida Abstract A voltammetric method for the determination of free and total sulfur dioxide in beer is described. First, volatile aldehydes (mainly acetaldehyde) are purged with nitrogen from a beer sample diluted in alkaline medium, collected in an appropriate electrolyte trapping solution and determined, after derivatization with hydrazine, by voltammetry using a hanging mercury drop electrode. Then, the remaining beer solution is strongly acidified and (total) sulfur dioxide is purged with nitrogen, collected in an appropriate electrolyte trapping solution and determined by voltammetry. The free sulfur dioxide concentration is calculated by difference between (total) sulfur dioxide and acetaldehyde concentrations. The proposed method has a relative standard deviation of about 2.1% and 4.4%, respectively for (total) sulfur dioxide and free sulfur dioxide concentrations normally found in beer, and results are in good agreement with those obtained by the p -rosaniline reference method. [source] Protein-based electrochemical biosensor for detection of silver(I) ions,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2010Sona Krizkova Abstract Silver(I) ions are extremely toxic to aquatic animals. Hence, monitoring of these ions in the environment is needed. The aim of the present study was to suggest a simple biosensor for silver(I) ions detection. The suggested biosensor is based on the modification of a hanging mercury drop electrode (HMDE) by the heavy metal binding protein metallothionein (MT) for silver(I) ions detection. Metallothionein accumulated for 120 s onto the HMDE surface. After rinsing the electrode, the biosensor (MT modified HMDE) was prepared prior to detection of silver(I) ions. The biosensor was immersed in a solution containing silver(I) ions. These ions were bound to the MT structure. Furthermore, the electrode was rinsed and transferred to a pure supporting electrolyte solution, in which no interference was present. Under these experimental conditions, other signals relating to heavy metals naturally occurring in MT were not detected. This phenomenon confirms the strong affinity of silver(I) ions for MT. The suggested biosensor responded well to higher silver(I) ion concentrations. The relative standard deviation for measurements of concentrations higher than 50,µM was approximately 2% (n,=,8). In the case of concentrations lower than 10,µM, the relative standard deviation increased to 10% (n,=,8). The detection limit (3,signal/noise) for silver(I) ions was estimated as 500,nM. Environ. Toxicol. Chem. 2010;29:492,496. © 2009 SETAC [source] Redox Potentials of Methanophenazine and CoB-S-S-CoM, Factors Involved in Electron Transport in Methanogenic Archaea,CHEMBIOCHEM, Issue 4 2003Mario Tietze Dr. Potentially important: The redox potentials of methanophenazine and CoB-S-S-CoM (see scheme), two cofactors from methanogenic archaea, strongly support the view that methanophenazine plays a central role in the electron transport system of methane-producing archaea. These redox potentials were measured with a hanging mercury drop electrode as the working electrode and were compared to those of several phenazine ethers. [source] Sensitive Electrochemical Detection of Native and Aggregated ,-Synuclein Protein Involved in Parkinson's DiseaseELECTROANALYSIS, Issue 13-14 2004Michal Masa Abstract The aggregation of ,-synuclein, a 14,kDa protein, is involved in several human neurodegenerative disorders, including Parkinson's disease. We studied native and in vitro aggregated ,-synuclein by circular dichroism (CD), atomic force microscopy (AFM) and electrochemical methods. We used constant current chronopotentiometric stripping analysis (CPSA) to measure hydrogen evolution catalyzed by ,-synuclein (peak H) at hanging mercury drop electrodes (HMDE) and square-wave stripping voltammetry (SWSV) to monitor tyrosine oxidation at carbon paste electrodes (CPE). To decrease the volume of the analyte, most of the electrochemical measurements were performed by adsorptive transfer (medium exchange) from 3,6,,L drops of ,-synuclein samples. With both CPE and HMDE we observed changes in electrochemical responses of ,-synuclein corresponding to protein fibrillization detectable by CD, fluorescence and AFM. Aggregation-induced changes in peak H at HMDE were relatively large in strongly aggregated samples, suggesting that this electrochemical signal may find use in the analysis of early stages of ,-synuclein aggregation. This assumption was documented by marked changes in the peak H potential and height in samples withdrawn at the end of the lag and the beginning of the elongation phase. Native ,-synuclein can be detected down to subnanomolar concentrations by CPSA. [source] | ||||||||||