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1.
A. Radi 《Fresenius' Journal of Analytical Chemistry》1999,364(6):590-594
The electrooxidation of nifuroxazide was investigated by cyclic and differential-pulse voltammetry at carbon paste and Sephadex-modified
carbon paste electrodes. Nifuroxazide is irreversibly oxidized at all pH values and gives rise to a well-defined oxidation
peak. The modification of the carbon paste surface with Sephadex allowed a preconcentration process to take place for nifuroxazide
such that higher sensitivity was achieved compared with the bare surface. The influence of the scan rate, time of accumulation,
modifier loading, solution conditions and pH on the adsorptive step at the modified carbon paste electrodes was investigated.
The direct determination of the drug in urine is also discussed.
Received: 2 June 1998 / Revised: 29 January 1999 / Accepted: 2 February 1999 相似文献
2.
A simple method for the determination of the urinary tract antibiotic nifuroxazide has been developed. The electrochemical reduction of the nitro group at mercury and carbon paste electrodes can be used for the determination with and without adsorptive preconcentration. The influence of parameters like pH of the background electrolyte, preconcentration potential and preconcentration time on the sensitivity of the method has been studied. Modification of the carbon paste by addition of nonpolar polystyrene/divinylbenzene particles has been investigated to enhance the adsorption properties of the surface. Concentrations as low as 10 ng/mL could be determined in urine without interferences. 相似文献
3.
A simple method for the determination of the urinary tract antibiotic nifuroxazide has been developed. The electrochemical
reduction of the nitro group at mercury and carbon paste electrodes can be used for the determination with and without adsorptive
preconcentration. The influence of parameters like pH of the background electrolyte, preconcentration potential and preconcentration
time on the sensitivity of the method has been studied. Modification of the carbon paste by addition of nonpolar polystyrene/divinylbenzene
particles has been investigated to enhance the adsorption properties of the surface. Concentrations as low as 10 ng/mL could
be determined in urine without interferences.
Received: 6 October 1997 / Revised: 22 January 1998 / Accepted: 26 January 1998 相似文献
4.
The voltammetric behaviour of chloroquine was investigated at carbon paste and dsDNA-modified carbon paste electrodes in different buffer systems over a wide pH range using cyclic and differential pulse voltammetry. Chloroquine was oxidized in the pH range 2.0-11.0 yielding one irreversible main oxidation peak. A second peak was also observed only in the pH range 5.0-7.0. The modification of the carbon paste surface with dsDNA allowed a preconcentration process to take place for chloroquine such that higher sensitivity was achieved as compared with the bare surface. The response was characterized with respect to solution pH, ionic strength, accumulation time and potential, chloroquine concentration, and other variables. Stripping voltammetric response showed a linear calibration curve in the range 1.0 × 10−7 to 1.0 × 10−5 mol l−1 with a detection limit of 3.0 × 10−8 mol l−1 at the dsDNA-modified electrode. Application of the modified electrode to serum, without sample pretreatment, resulted in good recovery higher than 95% and the higher standard deviation was 3.0%. 相似文献
5.
Mesoporous SiO2 of SBA-15 is reported to modify carbon paste electrodes for detecting epinephrine (EP). Carbon paste electrodes modified with synthesized SBA-15 show high sensitivity for voltammetric determination of EP, which is attributed to the strong adsorption ability of SBA-15 to EP and large surface area of the working electrode resulted from SBA-15 modification. The effects of pH value, amount of SBA-15 and scan rate were investigated. Under optimum conditions, the anodic peak current of EP was proportional to its concentration over the range from 1.0 × 10?6 to 6.0 × 10?5 mol L?1 and the limit of detection was 6.0 × 10?7 mol L?1. The results show mesoporous SiO2-modified carbon paste electrodes, particularly SBA-15-modificd electrodes, create new opportunities for sensitive, simple and suitable method in the electrochemical analysis of EP. 相似文献
6.
Voltammetric determination of Celiptium with carbon paste and lipid-modified carbon paste electrodes
The electrooxidation of the antitumour drug 2-methyl-9-hydroxyellipticinium (Celiptium) was investigated by cyclic, differential-pulse and adsorptive voltammetry at carbon paste (CPE) and lipid-modified carbon paste electrodes (LM-CPE). The influence of the paste composition, i.e., the ratio of graphite to binder, was studied in order to elucidate the nature of the accumulation process at the surface of the CPE. The electrode surface coverage at saturation was calculated. A.c. measurements at the CPE and at the LM-CPE during the accumulation of Celiptium demonstrated an increased differential double layer capacity of the LM-CPE. The influence of several parameters that affect the adsorptive step at the CPE was investigated, such as pH, ionic strength and interfering ions. Improved signals were obtained at the CPE and the detection limit in 0.1 M sodium perchlorate (tacc.=3 min) was found to be 2 × 10?10 M. Measurements of the drug in dilute standard serum samples were done using the medium-exchange technique. 相似文献
7.
《Electroanalysis》2004,16(20):1660-1666
The electrochemical behavior of the antibiotics rifampicin and rifamycin SV is investigated by cyclic voltammetry at carbon paste and in situ surfactant modified carbon paste electrodes. Both antibiotics adsorb on the unmodified electrodes and show a reversible redox process due to the oxidation of the 6,9‐dihydroxynaphthalene moiety to the corresponding naphthoquinone. This process is used as analytical signal for developing adsorptive voltammetric methods for the determination of the antibiotics. Experimental parameters, such as pH of the supporting electrolyte, accumulation potential and time are optimized. After accumulation from acidic solutions (0.1 M KCl pH 2 or HCl 0.2 M) at ?0.1 or 0 V for 3 min, the differential pulse oxidation peak current changes linearly with the antibiotic concentration in the range 3.5×10?10 M ?5.4×10?9 M or 5×10?11 M ?1.0×10?9 M for rifampicin and rifamycin SV, respectively. Rifamycin SV is not accumulated on carbon paste electrodes modified in situ with the anionic surfactant sodium dodecyl sulfate, whereas rifampicin is readily accumulated on this modified electrodes resulting in a signal enhancement and allowing rifampicin determinations without interference from rifamycin SV. On the other hand, selective determination of rifamycin SV in the presence of rifampicin is achieved by using carbon paste electrodes in situ modified with the cationic surfactant cetyltrimethylammonium chloride. 相似文献
8.
《Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)》1980,7(3):595-606
The electrochemical oxidation of three proteins: RNAase A, bovine serum albumin (BSA) and Concanavalin A, has been investigated on solid electrodes (gold, platinum, vitreous carbon, carbon paste electrode) using a.c. voltammetry and cyclic voltammetry. All the three proteins are adsorbed on these surfaces, but oxidation peaks on voltammograms are only well developed on carbon paste electrode (CPE), therefore the main experimental results presented here will refer to CPE. Tyrosinyl and tryptophanyl residues can first be oxidized over the range of pH 1 to 7; when oxidation potentials are more positive, other amino acids residues (histidine, cystine…) can also be oxidized. In both cases proteins adsorption is prerequisite. The adsorption mainly takes place at negative potentials (less than potential of zero charge) by the intermediary of electrostatic complex with the surface, this electrostatic adsorption is immediately followed by a rearrangement of the proteins at the electrode surface which leads to the formation of non electrostatic irreversible adsorbed complex. 相似文献
9.
J. Tashkhourian S. F. Nami Ana S. Hashemnia M. R. Hormozi-Nezhad 《Journal of Solid State Electrochemistry》2013,17(1):157-165
A modified carbon paste electrode was prepared by incorporating the TiO2 nanoparticles in the carbon paste matrix. The electrochemical behavior of gallic acid (GA) is investigated on the surface of the electrode using cyclic voltammetry and differential pulse voltammetry. The surface morphology of the prepared electrode was characterized using the scanning electron microscopy. The results indicate that the electrochemical response of GA is improved significantly at the modified electrode compared with the unmodified electrode. Furthermore, the capabilities of electron transfer on these two electrodes were also investigated by electrochemical impedance spectroscopy. Under the optimized condition, a linear dynamic range of 2.5?×?10?6 to 1.5?×?10?4?mol?L?1 with detection limit of 9.4?×?10?7?mol?L?1 for GA is obtained in buffered solutions with pH 1.7. Finally, the proposed modified electrode was successfully used in real sample analysis. 相似文献
10.
Prajwal Kumar Alex Joseph Praveen C. Ramamurthy Sankaran Subramanian 《Mikrochimica acta》2012,177(3-4):317-323
Glassy carbon electrodes (GCE) and carbon paste electrodes (CPE) were modified with imidazole functionalized polyaniline with the aim to develop a sensor for lead (II) in both acidic and basic aqueous solution. The electrodes were characterized by cyclic voltammetry and differential pulse adsorptive stripping voltammetry. The limit of detections obtained with glassy carbon electrode and carbon paste electrode are 20?ng?mL-1 and 2?ng?mL-1 of lead ion, respectively. An interference study was carried out with Cd(II), As(III), Hg(II) and Co(II) ions. Cd(II) ions interfere significantly (peak overlap) and As(III) has a depressing effect on the lead signal. The influence of pH was investigated indicating that bare and modified GCE and CPE show optimum response at pH?4.0 ± 0.05. Figure
Imidazole functionalized polyaniline modified glassy carbon and carbon paste electrodes were used for lead ion detection by using CV and DPASV techniques. The lower detection limit observed with GCE and CPE are 20?ng mL-1 and 2?ng mL-1. 相似文献
11.
A. Sánchez A. Zapardiel F.López de Prado E. Bermejo M. Moreno J. A. Pérez‐López M. Chicharro 《Electroanalysis》2007,19(16):1683-1688
A new analytical methodology for the electrochemical detection of the herbicide maleic hydrazide (3,6‐dihydroxypyridazine) by flow injection analysis is presented. This method is supported by the novel application of a palladium‐dispersed carbon paste electrode as an amperometric sensor for this herbicide. Maleic hydrazide shows anodic electrochemical activity on carbon‐based electrodes (glassy carbon or carbon paste electrodes) in all the pH range. This electrochemical activity is enhanced using metal‐dispersed carbon paste electrodes, especially at Pd‐dispersed CPE which displays good oxidation signals at 690 mV (0.050 M phosphate buffer pH 7.0), 140 mV lower than at unmodified electrodes. Under the optimized conditions, the electroanalytical performance of Pd‐dispersed CPE in flow injection analysis was excellent, with good reproducibility (RSD 3.3%) and a wide linear range (1.9×10?7 to 1.0×10?4 mol L?1). A detection limit of 1.4×10?8 mol L?1 (0.14 ng maleic hydrazide) was obtained for a sample loop of 100 μL at a fixed potential of 700 mV in 0.050 M phosphate buffer solution at pH 7.0 and a flow rate of 2.0 mL min?1. The proposed method was applied for the maleic hydrazide detection in natural drinking water samples. 相似文献
12.
Delia Gligor Izabella Craciunescu Ionel Catalin Popescu Lo Gorton 《Electroanalysis》2010,22(5):509-512
Carbon paste electrodes modified with a phenoxazine derivative, Meldola blue, and a phenothiazine derivative, methylene green, both strongly adsorbed on a synthetic zeolite were investigated using either glassy carbon powder (Sigradur K, SK) or single‐walled carbon nanotubes (SWCNT) as conductive electrode material. In the case of SWCNT based electrodes, the formal potential of both mediators was pH dependent, as expected for a redox process involving proton transfer. In contrast, the formal potential of both mediators of SK based modified electrodes was practically insensitive to pH. This behavior is discussed in terms of interactions existing in the heterogeneous system mediator‐zeolite‐electrode material. 相似文献
13.
Chicharro M Zapardiel A Bermejo E Moreno M Madrid E 《Analytical and bioanalytical chemistry》2002,373(4-5):277-283
Cobalt-phthalocyanine-modified carbon paste electrodes are shown to be excellent indicators for electrocatalytic amperometric measurements of triazolic herbicides such as amitrole, at low oxidation potentials (+0.40 V). The detection and determination of amitrole in flow injection analysis with a modified carbon paste electrode with Co-phthalocyanine is described. The concentrations of amitrole in 0.1 M NaOH solutions were determined using the electrocatalytic oxidation signal corresponding to the Co(II)/Co(III) redox process. A detection limit of 0.04 microg mL(-1) (4 ng amitrole) was obtained for a sample loop of 100 microL at a fixed potential of +0.55 V (vs. Ag/AgCl) in 0.1 M NaOH and a flow rate of 4.0 mL min(-1). Furthermore, the modified carbon paste electrodes offers reproducible responses in such a system, and the relative standard deviation was 3.3% using the same surface, 5.1% using different surface, and 6.9% using different pastes. The performance of the cobalt-phthalocyanine-modified carbon paste electrodes is illustrated here for the determination of amitrole in commercial formulations. The response of the electrodes is stable, with more than 80% of the initial retained activity after 50 min of continuous use. 相似文献
14.
Seung Mok Lee Zirlianngura Jamsheera Anjudikkal 《International journal of environmental analytical chemistry》2016,96(5):490-504
A sensitive and efficient electroanalytical method for trace determination of cadmium(II) was developed using hybrid material-modified carbon paste electrodes. The hybrid materials were obtained by modifying the commercial bentonite (BC) and locally collected clay (LC) using the hexadecyltrimethylammonium bromide (HDTMA) as to obtain the organo-modified clay samples (BH and LCH). Moreover, the local clay was pillared with aluminium and modified with the HDTMA (LCAH). The carbon paste electrode was modified with the BC/BCH/LC/LCH/LCAH hybrid materials. Cyclic voltammetric analytical data showed that the modified electrodes were possessed a characteristic reversible behaviour of Cd(II) in aqueous media. Moreover, a significant increase in cathodic or anodic current was obtained using the modified electrodes, BCH, LCH and LCAH. The electroactive surface area of modified electrodes was increased significantly compared to the pristine clay-modified carbon paste electrodes. The response of the modified electrode was not affected significantly varying the pH within the pH region 2.0–10.0. Fairly, a good linearity between the anodic current and concentration of Cd(II) (5.0–40 μg/L) was achieved using the modified electrodes (BCH, LCH and LCAH). The presence of different cations and anions as coexisting ions were studied in order to simulate the real water matrix measurements. Additionally, the real matrix analysis was simulated using the Cd(II) spiked tap water, which showed a good linearity between the concentration of Cd(II) and anodic current. 相似文献
15.
《Electroanalysis》2003,15(14):1204-1211
Two types of glassy carbon (GC) powder (i.e., Sigradur K and Sigradur G) have been mixed with mineral oil to obtain glassy carbon paste electrodes (GCPE's). The electrochemical behavior of such electrodes at different percentages of glassy carbon has been evaluated with respect to the electrochemistry of ferricyanide as revealed with cyclic voltammetry and the best paste composition was chosen. GC was then modified with Prussian Blue (PB), mixed at different percentages with unmodified GC and with a fixed amount of mineral oil in order to obtain PB modified glassy carbon paste electrodes (PB‐GCPE's). PB‐GCPE's with different percentages of GC modified with PB (PB‐GC) were compared and the dependence on the amount of PB on their performances was evaluated by studying the parameters of cyclic voltammetry (i.e., current peak, ΔEp, anodic and cathodic current ratio, charge density) and the amperometric response to H2O2. Data interpretation based on the GC surface area is presented. GCPE's with a selected amount of PB‐GC were then tested as H2O2 probes and all the analytical parameters together with the dependence on pH were evaluated. Some preliminary experiments with these electrodes assembled as glucose, lysine and lactate biosensors are also reported. 相似文献
16.
Toluidine Blue O (TBO) was covalently bound on silica gel and mixed with graphite powder and paraffin oil to produce modified carbon paste electrodes. The formal potential (E°′) of the covalently bound TBO was found to be −100 mV versus Ag|AgCl (KCl sat.) at pH 7.0 and the E°′ varied less than anticipated for a 2-electron-proton type mediator with pH. The bound TBO was found to act as an efficient electron acceptor for NADH as well as electron donor for oxidised horseradish peroxidase (HRP). The kinetics and the mechanism of the reaction between NADH and TBO were investigated with cyclic voltammetry and using a rotating disc electrode. Further experiments were done in the flow injection mode injecting different concentrations of NADH. Similar studies were done in the presence of hydrogen peroxide when HRP was adsorbed onto the TBO modified silica gel carbon paste electrodes. 相似文献
17.
A comparative study was made between developed chemically modified carbon paste electrodes and PVC membrane electrodes for the cationic surfactant cetyltrimethylammonium bromide (CTAB). The carbon paste electrode modified with cetyltrimethylammonium-tetrachloropalladate(II) (CTA-TClP) provides a more sensitive and stable device than that shown by electrodes with an inner reference solution. The best performance was obtained by an electrode based on the paste containing 3.6 wt% CTA-TCIP, 1.8 wt% ethylhexadecyldimethylammonium bromide, 37.6 wt% graphite and 57 wt% tricresyl phosphate. The sensor exhibited a Nernstian response for CTAB over a wide concentration range of 3.5 x 10(-7) to 1.0 x 10(-3) M with a detection limit of 2.0 x 10(-7) M between pH 2.7 and 8.2 with a fast response time of 相似文献
18.
Santos RH Santos NG Alves JP Garcia CA Romão LC Arguelho ML 《Bioelectrochemistry (Amsterdam, Netherlands)》2008,72(2):122-126
Rifampicin is an antibiotic which, on a carbon paste electrode, shows an oxidation response of 0.492 V (vs. Ag/AgCl) at pH 7.0, due to the electroactivity of the hydroquinone group. Interaction of rifampicin with chitosan is strongly dependent on pH, species concentrations and contact time between the latter. Compared to the carbon paste electrode, electrodes modified with chitosan showed greater sensitivity, with optimum voltammetric profile obtained at pH 8.0. Spectrophotometric measurements indicate that rifampicin is strongly absorbed by chitosan at pH less than the pKa of the pharmaceutical, such behaviour being favourable for the use of chitosan as a carrier for the controlled release of rifampicin in the intestinal tract. 相似文献
19.
Electrochemical Studies of Inclusion Complex Formed Between Glutathione and β‐cyclodextrin‐modified Carbon Electrodes and its Application for Determination of Glutathione
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Carolina Martínez‐Sánchez Luz M. Torres‐Rodríguez Ramón F. García‐de la Cruz 《Electroanalysis》2016,28(12):3055-3065
In this work, the electrochemical determination of glutathione (GSH) using β‐cyclodextrin (β‐CD) modified carbon electrodes was carried out. Different methodologies were used to modify the electrodes. In the first part of this paper, we analyze and compare the ability of the electrodes to determine GSH using the different β‐CD‐modified electrodes and cyclic voltammetry. We found that the carbon paste electrode modified by potential sweeping was the best electrode for GSH determination; in addition, we found that an inclusion complex formed between β‐CD deposited on the electrode surface and GSH. The formation constant for this complex was 2498.54 M?1 at 25 °C. Furthermore, we have also calculated thermodynamic parameters for the formation of the inclusion complex. In the second part of this paper, we analyze the effect of sweep rate and pH on the determination of GSH. The best results were obtained at a rate of 50 mV s?1 and a pH of 2.2. The β‐CD‐modified carbon paste electrode exhibits a linear response in a concentration range of 20 to 157 µM with a sensitivity of 1083.65 µA mM?1cm?2 and a detection limit of 3.92 µM. Finally, the electrode was used to determine the GSH concentration in Eichhornia crassipes root extract, and the concentration determination accuracy was validated by a well‐known spectroscopic method. 相似文献
20.
Pier Giorgio Desideri Daniela Heimler Luciano Lepri 《Journal of Electroanalytical Chemistry》1978,88(3):407-416
The electrochemical behavior of 3-amino-pyridine, 2,3-diamino-pyridine and 2,6-diaminopyridine has been investigated in the pH range 0.7–13 at platinum and carbon paste solid electrodes with periodical renewal of the diffusion layer. Electrolysis at controlled potential of 3-amino-pyridine and 2,3-diamino-pyridine have been carried out in the pH range 0.7–13. The formation, among the oxidation products of 3-amino-pyridine, in alkaline solutions, of 3,3′-azopyridine has been pointed out and the percentages of this compound at changing pH were reported. 相似文献