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1.
A. Radi 《Microchemical Journal》2002,72(1):35-41
Adsorption and reduction of rofecoxib were investigated by cyclic and square-wave voltammetry on a hanging mercury drop electrode in electrolytes of various pH values. The reduction process on hanging mercury drop electrodes gave rise to a single peak within the entire pH range (2.0-11.5). In alkaline solutions, rofecoxib gave a sensitive adsorptive reductive peak; approximately 10 times larger than those obtained by applying a square-wave scan without prior accumulation. Application of the method to the determination of rofecoxib in two pharmaceutical products (Vioxx 12.5 and 25 mg), without sample pretreatment, resulted in acceptable deviation from the stated concentrations. 相似文献
2.
This work is a study of the analytical utility of Nafion-modified microfabricated bismuth film electrodes (BiFEs) for the determination of Pb(II) and Cd(II) by anodic stripping voltammetry (ASV) in the presence of surfactants. Micro-fabricated BiFEs were prepared by depositing a thin film of bismuth on the surface of a silicon substrate by sputtering while the two-dimensional geometry of the final sensors was defined by photolithography. The BiFEs were further drop-coated with a Nafion film. These devices were applied to the determination of Pb(II) and Cd(II) by square wave ASV (SWASV) in the presence of Triton X-100 (a non-ionic surfactant), cetyltrimethylammonium bromide (CTAB) (a cationic surfactant) and sodium dodecyl sulphate (SDS) (an anionic surfactant). It was found that the presence of Nafion afforded an increase in sensitivity and the tolerance against surfactants but these properties were severely influenced by both the thickness of the Nafion film and the nature of the interfering surfactant. Using a Nafion of 0.4 μm thickness and 120 s of preconcentration, the repeatability (expressed as the % relative standard deviation on the same sensor (n = 8)) at the 20 μg l−1 level was 3.8% for Pb(II) and 3.1% for Cd(II) and the limits of detection were 0.5 μg l−1 for Cd(II) and Pb(II). The sensors were applied to Cd(II) and Pb(II) determination in a certified lake-water sample. 相似文献
3.
Jyh-Myng Zen Fu-Shien Hsu Nai-Yuen Chi Sen-Yuan Huang Mu-Jye Chung 《Analytica chimica acta》1995,310(3):407-417
The effect of various organic compounds on the Nafion/chelating agent mercury film electrodes (NCAMFEs) in square-wave anodic-stripping voltammetry (SWASV) is explored. Two chelating agents used to prepare the NCAMFEs are dimethylglyoxime and 2,2'-bipyridyl. Triton X-100, sodium dodecyl sulfate, albumin, gelatin, starch, camphor, and humic acid are used as model organic compounds, while cadmium, lead, and copper are used as test metal ions. The NCAMFEs are considerably more resistant to organic interferences than the Nafion-coated mercury film electrode. The implications of these interferences for the reliability and feasibility of stripping measurements using the NCAMFEs in real samples are discussed. Results presented for untreated urine and natural water samples demonstrate the analytical utility of the NCAMFEs in SWASV. 相似文献
4.
A Radi 《Microchemical Journal》2002,73(3):349-354
The adsorption and reduction behavior of lansoprazole has been studied by square-wave voltammetry at a hanging mercury drop electrode. A study of the variation in the reduction signal with solution variables, such as pH and concentration of lansoprazole, and instrumental variables, such as accumulation time and potential, frequency, pulse height and pulse amplitude, has resulted in optimization of the reduction signal for analytical purposes. The voltammetric procedure was successfully applied for rapid analysis of lansoprazole in stability studies without interference from the degradation products. It has also been used for the precise determination of lansoprazole in a pharmaceutical preparation. 相似文献
5.
Adsorptive stripping voltammetric determination of trace concentrations of molybdenum at an in situ plated lead film electrode 总被引:1,自引:0,他引:1
An in situ plated lead film electrode has been applied for adsorptive stripping voltammetric determination of trace concentrations of molybdenum in the presence of Alizarin S. The procedure is based on the preconcentration of the molybdenum-Alizarin S complex at an in situ plated lead film electrode held at −0.6 V (versus Ag/AgCl), followed by a negatively sweeping square wave voltammetric scan. The peak current is proportional to the concentration of molybdenum over the range 2 × 10−9 to 5 × 10−8 mol L−1, with a 3σ detection limit of 9 × 10−10 mol L−1 with an accumulation time of 60 s. The measurements were carried out from underaerated solutions. The proposed procedure was validated in the course of Mo(VI) determination in water certified reference materials. 相似文献
6.
Pacheco WF Miguel EM Ramos GV Cardoso CE Farias PA Aucélio RQ 《Analytica chimica acta》2008,625(1):22-27
In this work, a new approach is presented to allow interference-free determination of Cu (II) by stripping voltammetry using the bismuth-film electrode. The addition of hydrogen peroxide to the electroanalytical cell has promoted complete resolution between re-dissolution peaks of Bi (III) and Cu (II). The absence of interference could be evaluated by the correlation coefficient (r > 0.99) between Cu (II) concentration and its shifted current peak (at +212 mV) while achieving a slightly fluctuation of the bismuth current peak at −180 mV. Studies were performed aiming towards the optimum conditions for trace determination of Cu (II) using hydrogen peroxide. The methodology was applied to a real sample (sugarcane spirits) and the results were compared to those from graphite furnace atomic absorption spectrometry. The analytical parameters of merit and the results of the analysis indicated that the analytical methodology could be readily used for trace determination of Cu (II). 相似文献
7.
The voltammetric behavior of sulfadimetoxol (SDX) was studied by square-wave techniques, leading to two methods for its determination in aqueous samples and veterinary formulations. The application of the square-wave mode shows the determination of SDX between 1 × 10−7 M and 2 × 10−6 M at −0.60 V and for the stripping voltammetry of adsorbed SDX with an accumulation step of 15 s proved to be more sensitive, yielding signals five times larger than those obtained without the accumulation. The determination of SDX was done between 2 × 10−8 M and 5 × 10−7 M by stripping mode. The relative standard deviations obtained for concentration levels of SDX as low as 3 × 10−7 M with square-wave was 3.4 % (n = 8) and for 2 × 10−7 M with stripping square-wave was 3.1 % (n = 8). The methods were satisfactorily applied for determining SDX in four veterinary products. 相似文献
8.
The most essential limitation of batch-injection analysis (BIA) methodology compared to other flow methods (CFA, FIA, SIA) is the lack of possibility of on-line sample processing in the measuring system. Some procedures of on-line sample pretreatment in BIA are possible by changing the plastic tip of the automatic micropipette used for sample injection into a flow-through reactor, e.g. by packing it with a bed of a solid sorbent. This concept is employed in the voltammetric stripping determinations of trace metals using a bed of commercial chelating resin Chelex-100. It was found that, besides the electrochemical preconcentration of analytes in the form of amalgams on the surface of mercury thin film electrodes, an approximately 10-fold additional preconcentration can be achieved on the packed sorbent bed by using different volumes of aspirated sample solution and eluent. This procedure allows also efficient elimination of some matrix effects. 相似文献
9.
Cathodic adsorptive stripping voltammetric behaviour of guanine in the presence of copper at the static mercury drop electrode 总被引:1,自引:0,他引:1
The cathodic adsorptive electrochemical behavior of guanine in the presence of some metal ions at the static mercury drop electrode was investigated. A 1.0×10−3 mol l−1 NaOH or a 2.0×10−2 mol l−1 Hepes buffer at pH 8.0 solutions were used as supporting electrolytes. The reduction peak potential for guanine was found to be around −0.15 V, which is very close to the mercury reduction wave. A new peak appears at −0.60 V in the presence of copper or at −1.05 V in the presence of zinc. A square wave voltammetric procedure for electroanalytical determination of guanine in 2.0×10−2 mol l−1 Hepes buffer at pH 8.0 containing 1.6×10−5 mol l−1of copper ions, was developed. An accumulation potential of −0.15 V during 270 s for the prior adsorption of guanine at the electrode surface was used. The response of the system was found to be linear in the range of guanine concentration from 6.62×10−8 to 1.32×10−7 mol l−1 and the detection limit was 7.0×10−9 mol l−1. The influence of DNA bases such as adenine, cytosine and thymine was also examined. Cyclic voltammetry was used to characterize the interfacial and redox mechanism. 相似文献
10.
Maria V. Tsymbal Iva Ya. Tuijan Zaual A. Temerdashev Khjena Z. Brainina 《Electroanalysis》1994,6(2):113-117
The similarity in the structures (presence of hexatomic rings) of crown ethers and graphite is used for adsorptive modification of the graphite electrode surface. The effect is exploited in stripping voltammetry for the determination of palladium. Anodic currents observed at potentials of 0.6 to 0.65 V (vs. Ag/AgCI electrode) are the source of information about adsorption of the crown ethers. Maximum adsorption of the reagents takes place at potentials close to the potential of zero charge of graphite. Deposition of palladium on the electrode surface is enhanced, the closer the values of the diameters of the crown-ether rings and Pd(II) are. 相似文献
11.
A simple, fast and sensitive arsenic speciation method has been developed for environmental water analysis by using differential pulse cathodic stripping voltammetry (CSV) performed on a hanging mercury drop electrode (HMDE). Electroactive As(III) is determined by direct CSV analysis. As(V) is converted to As(III) species first and is subsequently quantified by the concentration difference between total inorganic arsenic and As(III). A new batch-mode As(V) reduction procedure by l-cysteine was developed in this study. The optimized parameters for quantitative As(V) reduction include treatment with 20 mM l-cysteine and 0.03 M HCl for 6 min at 70 °C. Organic arsenic, including monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), can be decomposed to As(V) through UV photooxidation with peroxydisulfate and quantified through subtracting total inorganic arsenic from the total arsenic. At optimum condition, the detection limits for As(III), As(V), and organic arsenic (MMA and DMA) were all 0.3 μg/L and with the linear range from 2.5 to 190 μg/L. Interference from ions common in natural water (Mn, Fe, Cr, Cd, Ca, Zn, Mg, and phosphate) is minimal. The method was validated by analyzing the NIST 1640 natural water standard reference material and by recovery tests on spiked tap water and groundwater. When applied to on-site analysis of sediment pore water and stream water, the CSV results agree well with those obtained by inductively coupled plasma–mass spectrometry (ICP–MS) and graphite furnace atomic absorption spectrometry (GFAAS) methods. 相似文献
12.
Multicriteria optimization, widely used in engineering, does not much used in the optimization of analytical signals. The aim of this paper is to show the usefulness of the desirability function to optimize instrumental responses obtained in instrumental analysis. The simultaneous optimization of a signal and of its variability is a generic question of interest to any chemical analyst. It is clear that the improvement of the two responses forms the basis of the validation of any analytical method, and affects all the figures of merit: accuracy (trueness and precision), capability of detection, robustness, sensitivity, etc. Furthermore, in the specific case of electroanalysis, an improvement in the signal may implicitly mean an increase of the signal in the blank, such that the “net signal” may not improve. This experimental approach (surface response methodology plus desirability) to multicriteria optimization has been applied to three cases of growing complexity. Thus, in the determination of Cu(II) by differential pulse anodic stripping voltammetry the simultaneous maximization of the peak current and minimization of its standard deviation is looked for. Whereas, in the determinations of Ni(II) and indomethacin by differential pulse adsorptive stripping voltammetry, the simultaneous maximization of the peak current and minimization of the blank signal is desired. In all the cases, the experimental conditions where the optima are found for each individual response are just opposite, so it is required to look for a certain compromise, that is achieved using the desirability function. 相似文献
13.
The paper presents the first report on fabrication and application of a user friendly and mercury free electrochemical sensor, with the renewable bismuth bulk annular band working electrode (RBiABE), in stripping voltammetry (SV). The sensor body is partly filled with the internal electrolyte solution, in which the RBiABE is cleaned and activated before each measurement. Time of the RBiABE contact with the sample solution is precisely controlled. The usefulness of this sensor was tested by Ni(II) and Co(II) traces determination by means of differential pulse adsorptive stripping voltammetry (DP AdSV), after complexation with dimethylglyoxime (DMG) in ammonia buffer (pH 8.2). The experimental variables (composition of the supporting electrolyte, pre-concentration potential and time, potential of the RBiABE activation, and DP parameters), as well as possible interferences, were investigated. The linear calibration graphs for Ni(II) and Co(II), determined individually and together, in the range from 1 × 10−8 to 70 × 10−8 mol L−1 and from 1 × 10−9 to 70 × 10−9 mol L−1 respectively, were obtained. The calculated limit of detection (LOD), for 30 s of the accumulation time, was 3 × 10−9 mol L−1 for Ni(II) in case of a single element’s analysis, whereas the LOD was 5 × 10−9 mol L−1 for Ni(II) and 3 × 10−10 mol L−1 for Co(II), when both metal ions were measured together. The repeatability of the Ni(II) and Co(II) adsorptive stripping voltammetric signals obtained at the RBiABE were equal to 5.4% and 2.5%, respectively (n = 5). Finally, the proposed method was validated by determining Ni(II) and Co(II) in the certified reference waters (SPS-SW1 and SPS-SW2) with satisfactory results. 相似文献
14.
The determination of zinc ion (1-60 ng ml−1) by anodic square-wave stripping voltammetry on an anion-exchange perfluorinated polymer Tosflex mercury film electrodes (TMFE) was evaluated. The detection limit was 0.1 ng ml−1 Zn(II). The effect of various organic compounds (gelatin, albumin, starch, camphor, humic acid, Triton X-100, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB)) is explored. The results indicate that due to the size-exclusion and ion-exchange properties of Tosflex film, the TMFE is considerably more resistant to organic interference than the bare mercury film electrode. 相似文献
15.
吸附转移溶出伏安法测定氟罗沙星注射液含量 总被引:2,自引:0,他引:2
氟罗沙星 (fleroxacin ,FLRX)是一种抗菌谱广 ,杀菌力强的三氟喹诺酮类抗菌药[1] 。FLRX含量的测定方式主要有HPLC法[2 ,3] 、紫外分光光度法[3,4 ] 和荧光分光光度法[5] 。本文研究FLRX在不同支持电解质中的电化学行为 ,发现其在石墨电极表面有很强的吸附性 ,在一定的电位下富集几分钟 ,电极冲洗后在底液中扫描 ,仍有很大的峰电流。在此基础上建立了吸附转移溶出伏安法(AdTSV) [6 ] 测定FLRX。方法的线性范围为 4~42 μg/ml,用于FLRX葡萄糖注射液中FLRX含量的测定 ,比其他方法灵敏、准确、… 相似文献
16.
Two sequential injection systems have been developed for adsorptive stripping voltammetric measurement. One is for substances adsorbing at mercury, e.g. riboflavin. In this case, a simple arrangement with only sample aspiration is needed. Reproducibility was 3% and detection limit 0.07 μM. The measuring system was applied to determination of riboflavin in vitamin pills and to study the photodegradation process of riboflavin in aqueous solutions. In the second case, metal ions were determined. They have to be complexed before deposition on the mercury surface. Thus, both the sample and the ligand have to be aspirated in the system. In this case, the reproducibility was ≈6% and the detection limit <0.1 ppm for cadmium, lead and copper when complexation with oxine was used. Dimethylglyoxime was used in determination of nickel and cobalt and nioxime complexes were used in determination of nickel and copper. With these complexing agents, the reproducibility was the same as with oxine, but the metals could be determined at concentrations lower than 0.01 ppm. Application of two ligands in a SIA system with AdSV detection was also studied. Simultaneous determination of copper, lead, cadmium and cobalt was possible by using oxine and dimethylglyoxime. Copper and nickel were simultaneously determined by using dimethylglyoxime and nioxime. 相似文献
17.
The voltammetric behaviour of Imatinib (STI 571) and its main metabolite (N-demethylated piperazine derivative) were studied by square-wave techniques, resulting in to two methods for their determination in aqueous and urine samples at pH 2. The application of the square-wave (SW) without the adsorptive accumulation and voltammetric stripping (AdSV) exhibit a peak at a reduction potential of −0.70 V for an accumulation potential of −0.45 V. The sensitivity was higher for the stripping technique because a signal four times higher than that provided by the square-wave method without the previous accumulation was obtained. Due to the fact that Imatinib and its metabolite show the same voltammetric reduction process, some experiments were performed in order to compare the voltammetric response of Imatinib and its main metabolite in a similar ratio than that of the therapeutic concentration. The calibration curve for Imatinib in urine was linear in the range from 1.9 × 10−8 to 1.9 × 10−6 M in stripping mode with an accumulation time (tacc) of 10 s. The relative standard deviations obtained for concentration levels of Imatinib as low as 2.0 × 10−7 M for square-wave was 2.17% (n = 9) and for stripping square-wave was 2.65% (n = 9) in the same day. The limits of detection for square-wave and stripping square-wave were 5.55 × 10−9 and 5.19 × 10−9 M, respectively. Thus, the presented method are straightforward, rapid and sensitive and has been applied to the determination of Imatinib and its main metabolite altogether in urine samples from real patients. 相似文献
18.
Electrochemical studies of famotidine were carried out using voltammetric techniques: cyclic voltammetry, linear sweep and square wave adsorptive stripping voltammetry. The dependence of the current on pH, buffer concentration, nature of the buffer, and scan rate was investigated. The best results for the determination of famotidine were obtained in MOPS buffer solution at pH 6.7. This electroanalytical procedure enabled to determine famotidine in the concentration range 1 × 10−9–4 × 10−8 mol L−1 by linear sweep adsorptive stripping voltammetry (LS AdSV) and 5 × 10−10–6 × 10−8 mol L−1 by square wave adsorptive stripping voltammetry (SW AdSV). Repeatability, precision and accuracy of the developed methods were checked. The detection and quantification limits were found to be 1.8 × 10−10 and 6.2 × 10−10 mol L−1 for LS AdSV and 4.9 × 10−11 and 1.6 × 10−10 mol L−1 for SW AdSV, respectively. The method was applied for the determination of famotidine in urine. 相似文献
19.
A new automated batch method for the determination of ultratrace metals (nanogram per liter level) was developed and validated. Instrumental and chemical parameters affecting the performance of the method were carefully assessed and optimized. A wide range of voltammetric methods under different chemical conditions were tested. Cadmium, lead and copper were determined by anodic stripping voltammetry (ASV), while nickel, cobalt, rhodium and uranium by adsorptive cathodic stripping voltammetry (AdCSV). The figures of merit of all of these methods were determined: very good precision and accuracy were achieved, e.g. relative percentage standard deviation in the 4-13% for ASV and 2-5% for AdCSV.The stripping methods were applied to the determination of cadmium, lead, copper, nickel, cobalt, rhodium and uranium in lake water samples and the results were found to be comparable with ICP-MS data. 相似文献
20.
The behavior of epinephrine on a carbon fiber microelectrode (CFME) was studied with cyclic voltammetry and square-wave (SW) stripping voltammetry in order to find optimum conditions for its analysis using the CFME. An anodic stripping peak at about 0.20 V (vs. Ag/AgCl) was utilized. Under optimum conditions for anodic stripping (a pH value of 7.4, a deposition potential of − 0.5 V, a deposition time of 90 s, a final potential of 0.8 V, a SW frequency of 20 Hz, a step potential of 5 mV, and an amplitude of 45 mV), the calibration was linear in the concentration range of 0.0∼0.4 mg/L, and the detection limit was found to be 0.009 mg/L with a relative standard deviation 0.18% (n = 12) at 0.2 mg/L. The analytical performance of the CMFE, which is unmodified, is comparable to or better than other voltammetric results with various modified electrodes. 相似文献