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Carbon nanosheets load beta-cyclodextrin (β-CD-CNS) as a new modified electrode materials was reported for the electrochemical determination of sulfadiazine(SD). Carbon nanosheets(CNS) were prepared by a new method of ultrasonic electrolysis in which the β-CD was attached on CNS through ultrasonic dispersion method. The β-CD-CNS composite nanomaterials were immobilized onto glassy carbon electrodes with drops of coating method to construct an SD voltammetric sensor. The differential pulse stripping voltammetry (DPSV) was used to characterize the electrocatalytic behavior of the developed sensor. The Effects of some parameters on the response behavior of the sensor such as pH,modification amount,scanning rate,stirring speed,stirring time,deposition potential and time were investigated and optimized. The results indicated that the β-CD-CNS composite nanomaterials had excellent electroactivity for the SD in neutral solution and greatly improved the current response of SD. Under the optimal conditions, the SD had an irreversible characteristic oxidation peak around+0.87 V,and the oxidation peak current ip(μA) had a good linear relationship with the concentration C ( μmol/L) of the SD in concentration range of 0.05 μmol/L-13.5 μmol/L with correlation coefficients of 0.999. The detection limit was 12.2 nmol/L (S/N=3). The sensor was successfully applied for the trace SD determination in water and milk samples and the recoveries from the spiked samples were 80.0%-102% with RSD≤5.2%.
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A silver nanowires(AgNWs) flexible electrode was prepared using polydimethylsiloxane (PDMS) as the substrate and AgNWs as the conductive layer. It is easier to change the shapes and sizes of the flexible electrode due to its excellent stretchability and foldability. A square wave stripping voltammetry (SWSV) method for the detection of trace copper in water was established using the electrode as the working electrode.The characterization of AgNWs flexible electrode showed that the spread of AgNWs was uniform and the average resistance was 1.03 Ω. The data of electrochemical analysis showed that the properties of the electrode were superior to commercialized gold electrode and silver electrode. The effects of Bi3+concentration, supporting electrolyte,pH value, enrichment potential and enrichment time were determined and optimized. We achieved the sharpest and highest peak of the SWSV curves for the detection of Cu2+in the range of-0.3-0.3 V,which means the most sensitive detection, under the following conditions such as 0.5 mg/L Bi3+,0.1 mol/L support electrolyte tartaric acid-sodium tartrate solution (pH, 4.8), 0.6 V of enrichment potential, and 600 s of enrichment time. Under such conditions, the linear detection range of Cu2+concentration was from 0.001 mg/L to 0.100 mg/L and the detection limit was 9.27×10-5mg/L. The advantages of this detection method are fast speed,high sensitivity and wide detection range. Therefore,it can not only meet the requirements for the copper ion detection but also provide a new method or experimental basis for the detection of other metal ions in water. In addition, the AgNWs flexible electrode has great potential in detections under special circumstances or instantaneous detections due to its wonderful flexibility and biocompatibility.
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Bismuth modified boron doped diamond (BDD) film electrode was employed for simultaneous determination of trace ZnⅡ,CdⅡand PbⅡby anodic stripping voltammetry.BiⅢwas simultaneously in-situ deposited on bismuth modified boron doped diamond electrode with ZnⅡ,CdⅡ and PbⅡ by pre-concentration.In the presence of BiⅢ,the sensitivity for determination of ZnⅡ,CdⅡ and PbⅡ was remarkably enhanced.Influence factors such as bismuth concentration,boron doped concentrations of BDD electrode,pH,preconcentration potential were investigated and optimized.Under the optimal conditions,the stripping peak currents increased linearly with the increasing concentration of ZnⅡ,CdⅡ and PbⅡ in the range of 10-300 μg/L.The limit of detection was 0.56 μg/L for ZnⅡ,0.32 μg/L for CdⅡand 0.75 μg/L for PbⅡ (S/N=3),respectively.The interference experiments showed that common ions had little influence on the determination except CuⅡ.In addition,the developed electrode displayed a good repeatability.The method was successfully applied to determination of ZnⅡ,CdⅡ and PbⅡ in real water samples with the standard addition recoveries of 92.0%-114.0%.
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@#A sandwiched electrochemical immunoassay based on the AuNPs@GSH-CdTe as a signal label, which formed by GSH-CdTe QDs and AuNPs, with dual signal amplified by reduced graphene oxide and AuNPs was proposed for the sensitive detection of prostate specific antigen(PSA). Through a sandwich immunoreaction, the target PSA and AuNPs@GSH-CdTe labeled Ab1 were captured to rGO/AuNPs-Ab2 surface. After the HNO3-dissolution step, square wave stripping voltammetry(SWSV)analysis of the captured CdTe QDs was used to quantify the concentration of PSA. In this system, AuNPs possessedlarge specific surface and good biocompatibility, which could effectively expand the amount of antigen and GSH-CdTe QDs loading and signals amplifying, while rGO played a synergistic amplification role due to its large specific surface. The proposed method showed good linearity ranging from 0. 5 to 200 ng/mL with the detection limits of 5. 0 pg/mL. It also showed excellent selectivity, good reproducibility, satisfactory stability. In addition, the method was successfully applied to the determination of real samples. The result was satisfactory and the recovery could fall in 98. 20%- 106. 2%, which represented a novel approach for versatile detection of tumor markers.
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An electrochemically pretreated silver macroporous (Ag MP) multiwalled carbon nanotube modified glassy carbon electrode (PAN-Ag MP-MWCNT-GCE) was fabricated for the selective determination of an anti-hyperlipidimic drug, pitavastatin (PST). The fabricated electrochemical sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated electrode was employed in quantifying and determining PST through differential pulse adsorptive stripping voltammetry (DPAdSV) and CV. The electrode fabrication proceeded with remarkable sensitivity to the determination of PST. The effect of various optimized parameters such as pH, scan rate (ν), accumulation time (tacc), accumulation potential (Uacc) and loading volumes of Ag MP-MWCNT suspension were investigated to evaluate the performance of synthesized electrochemical sensor and to propose a simple, accurate, rapid and economical procedure for the quantification of PST in pharmaceutical formulations and biological fluids. A linear response of PST concentration in the range 2.0×10?7–1.6×10?6 M with low detection (LOD) and quantification (LOQ) limits of 9.66 ± 0.04 nM and 32.25 ± 0.07 nM, respectively, were obtained under these optimized conditions.
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ZnO nanotubes were prepared via electrospinning the Zn ( AC ) 2-polyacrylonitrile-polyvinylpyrrolidone ( PAN-PVP) precursor, followed by thermal decomposition of the above polymers from the precursor fibers. SEM and XRD characterization confirmed that the as-prepared ZnO nanofibers presented the hollow nanotube form, which was composed of ZnO nanoparticles with the size of about 40 nm in wurtzite crystal structure. By mixing with graphene, the obtained ZnO-graphene composite modified glassy carbon electrode ( ZnO-RGO/GCE ) was successfully constructed by dip-coating, which was used for the determination of Pb2+in water. With the sensitive response of the ZnO-RGO/GC electrode to Pb2+in solution was demonstrated by square wave stripping voltammetry, the response pctential was at -0. 4V. Under the optimized conditions, a good linear relationship between peak current and Pb2+ concentration was obtained in the range of 2. 4×10-9-4. 8×10-7 mol/L (R=0. 9970) by 10 min preconcentration at -1. 0 V in 0. 1 mol/L HAc-NaAc buffer solution (pH=4. 6). The detection limit was 4. 8×10-10 mol/L (S/N>3). The ZnO-RGO/GC electrode had good stability. The practical analytical application of the ZnO-RGO modified electrode was assessed by the measurement of the actual water sample and the result was consistent with that obtained by ICP-MS.
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This study was aimed to develop a simultaneous determination of zinc and cadmium with carbon fiber electrode by linear sweep stripping voltammetry. Effects of analytical base solution, accumulation potential, ac-cumulation time and scanning velocity were also investigated on the determination. The results showed that in 1 mol·L-1 H2SO4 medium solution, zinc and cadmium had good electrochemical response on the carbon fiber electrode and appeared sensitive anodic stripping peaks at-0.97 V and-0.77 V, respectively. The anodic stripping peak cur-rents and concentrations of zinc and cadmium showed good linear relationships, with correlation coefficients R2 of 0.996 5 and 0.995 4, respectively. The detection limits of zinc and cadmium (S/N=3) were 1.5×10-9 mol·L-1 and 1.0×10-10 mol·L-1, respectively. The average recoveries of zinc and cadmium were 98.9%and 98.1%with the rela-tive standard deviations (RSD) of 2.72%and 2.45%(n=6), respectively. It was concluded that the method of simul-taneous determination of zinc and cadmium with carbon fiber electrode was simple, sensitive and accurate.
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The mutual influence of lead and cadmium ions on “in-situ” bismuth film coated glassy carbon electrode was demonstrated using different concentration target ions by changing ratio between Pb2+ and Cd2+. It is found that the presence of coexisting ions can have an influence on the detection of target ions. Especially for the detection of Cd2+, the existence of Pb2+ can be beneficial for the deposition of Cd due to the more positive deposition potentials. And the analytical performances of Cd2+and Pb2+ were obtained. The detection limit is 0. 5 μg/L towards Pb2+ with a linear range from 1-80 μg/L using 60 s deposition time. The resulting calibration plots of Cd2+ are linear over the range from 1-25 and 30-200 μg/L with the detection limit of 1 μg/L using 120 s deposition time. The bismuth film was finally employed to determine the Pb2+and Cd2+in real sample with good satisfied results.
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A novel electrochemical method based on dehydroabietylamine schiff base( DBS) and multi-walled carbon nano-tubes( MWCNTs) composite modified glassy carbon electrode was presented for determination of Pb2+. The electrochemical behaviors of Pb2+on the modifled electrode were investigated by cyclic voltammetry ( CV) and differential pulse anodic stripping voltammetry ( DPASV ) . The results showed that under the optimized conditions including 0 . 2 mol/L NaAc-HAc used as supporting buffer ( pH 5 . 5 ) , -1 . 1 V of accumulating potential, 250 s of accumulating time, the oxidation peak current was proportional to Pb2+concentration in the range between 1 × 10-8 mol/L and 1 × 10-6 mol/L with the linear regression equation as I(μA)= 6. 6173c(μmol/L)+0. 2597(R=0. 9971) and the detection limit as 5. 0×10-9 mol/L (S/N=3). The proposed sensor was successfully employed to determine Pb2+ in real samples with satisfactory results. In addition, this method showed the advantages of simple operation, short assay time, good accuracy, satisfactory efficiency and good selectivity for determination of low concentration lead in water samples.
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ZnO nanoparticle-containing carbon composite nanofiber ( ZnO-CNF ) was prepared by the electrospinning of the ZnCl2-PAN precursor, followed by preoxidation and carbonization. The ZnO nanoparticles were uniformly distributed on the surface of the carbon nanofiber with the size of 20-30 nm, confirmed by scanning electron microscopy ( SEM ) . The wettability of the ZnO-CNF was studied by water contact angle test. With Nafion as an additive, the ZnO-CNF modified electrode was successfully constructed by dip-coating. The surface morphology and electrochemical properties of the modified electrode were investigated by SEM and cyclic voltammetry. There was a sensitive response of the ZnO-CNF modified electrode on Pb ions in solution, demonstrated by square wave stripping voltammetry. Under the optimized conditions, a good linear relationship between peak current and Pb2+concentration was obtained in the range of 2. 4×10-10-2. 4×10-7 mol/L (R=0. 998) by 10 min preconcentration at -1. 0 V in 0. 1 mol/L NaAc buffer solution (pH=4. 6). The detection limit was 4. 8×10-11 mol/L. The practical analytical application of the ZnO-CNF modified electrode was assessed by the measurement of the actual water sample and the result was consistent with that obtained by ICP-MS.
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A method of detecting lead was developed using square wave anodic stripping voltammetry (SWASV) with DNA-carbon nanotube paste electrode (CNTPE). The results indicated a sensitive oxidation peak current of lead on the DNA-CNTPE. The curves were obtained within a concentration range of 50 ngL-1-20 mgL-1 with preconcentration time of 100, 200, and 400 sec at the concentration of mgL-1, microgL-1, and ngL-1, respectively. The observed relative standard deviation was 0.101% (n = 12) in the lead concentration of 30.0 microgL-1 under optimum conditions. The low detection limit (S/N) was pegged at 8 ngL-1 (2.6 x10-8 M). Results showed that the developed method can be used in real-time assay in vivo without requiring any pretreatment and pharmaceutical samples, and food samples, as well as other materials requiring water source contamination analyses.
Subject(s)
Electrodes , Limit of Detection , Nanotubes , Plants , WaterABSTRACT
This study describes a simple and sensitive voltammetric method for determining As (III) and As (V)concentrations in ìg.L-1. Electroactive As (III) is evaluated by direct analysis. As (V) is converted into As (III) using reduction solution; the new As (III) concentration, represents the total inorganic As in the analyzed sample. As (III) and total inorganic As determination showed a work potential peak at -0.68 V;As (V) concentration was determined by subtraction [total inorganic As As (III)]. Quantification and detection limits for As (III) were 0.22 and 0.08 ìg.L-1, respectively, for a deposition time of 180 s with the linear range from 1 to 5 ìg.L-1. Standard deviation for 1 to 5 ìg.L-1 arsenic concentration (n = 10) was 5%.The methodology was successfully applied for identifying and quantifying the inorganic arsenic in grape juices; and the accuracy was assessed by a recovery test on spiked samples, being 98.2% for As (III) and 96.4% for As (V). These results were compared with those from hydride generation atomic absorptions pectrometry analyses. The grape juice samples analyzed by voltammetric technique showed As (III) and As (V) concentrations ranging 51-71 ìg.L-1 and 34-60 ìg.L-1, respectively.
Subject(s)
Arsenic , JuicesABSTRACT
PURPOSE: Thallous-201 chloride produced at Korea Cancer Center Hospital(KCCH) is used in detecting cardiovascular disease and cancer. Thallium impurity can cause emesis, catharsis and nausea, so the presence of thallium and other metal impurities should be determined. According to USP and KP, their amounts must be less than 2 ppm in thallium and 5 ppm in total. In this study, the detection method of trace amounts of metal impurities in [201Tl]TlCl injection with polarography was optimized without environmental contamination. MATERALS AND METHODS: For the detection of metal impurities, Osteryoung Square Wave Stripping Voltammetry method was used in Bio-Analytical System (BAS) 50W polarograph. The voltammetry was composed of Dropping Mercury Electrode (DME) as a working electrode, Ag/AgCl as a reference electrode and Pt wire as a counter electrode. Square wave stripping method, which makes use of formation and deformation of amalgam, was adopted to determine the metal impurities, and pH 7 phosphate buffer was used as supporting electrolyte. RESULTS: T1, Cu and Pb in thallous-201 chloride solution were detected by scanning from 300 mV to -800 mV. Calibration curves were made by using TlNO3, CuSO4 and Pb(NO3)2 as standard solutions. Tl was confirmed at -450 mV peak potential and Cu at -50 mV. Less than 2 ppm of Tl and Cu was detected and Pb was not detected in KCCH-produced thallous-201 chloride injection. CONCLUSION: Detection limit of thallium and copper is approximately 50 ppb with this method. As a result of this experiment, thallium and other metal impurities in thallous-201 chloride injection, produced at Korea Cancer Center Hospital, are in the regulation of USP and KP. Polarograph could be applied for the determination of metal impurities in the quality control of radiopharmaceuticals conveniently without environmental contamination.
Subject(s)
Calibration , Cardiovascular Diseases , Catharsis , Copper , Electrodes , Hydrogen-Ion Concentration , Korea , Limit of Detection , Metals, Heavy , Nausea , Polarography , Quality Control , Radiopharmaceuticals , Thallium , VomitingABSTRACT
Objective To establish a new method for determination of Pb and Cd in sewage.Methods The contents of Pb and Cd in sewage were simultaneously determined by linear sweep anodic stripping voltammetry in0.1mol/L HCl -0.1mol/L KCl solution.Results The peak potentials of Pb and Cd appeared at-588mV and-780mV respectively.The recovery rates and precisions(RSD%)of Pb and Cd were90.0%-110.0%,91%-109.5%and0.41%-4.24%,0.56%-7.03%respectively.The lin-ear range of Pb and Cd was0.005-0.2mg /L.Conclusion This method could be applied for determination of Pb and Cd in sewage.
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Objective To establish a method for determination of lead in cosmetics. Methods Samples were digested. The lead content was detected by isochronous mercury-plating method with the condition of lead cation being enriched for 40 s at -1.20V(vs. SCE). Results The stripping potential peak of lead appeared at - 0. 20 V( vs. SCE) . The detection limit was 0.03 jug Pb. Six parallel determinations of a sample were done with the mean of 3.574mg/ kg and the relative standard deviation of 4. 1% . Recovery rates obtained by standard addition test ranged from 90% -100.5% . Conclusion The method is suitable for detecting lead in cosmetics.
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AIM:A voltammetric method was developed for the determination of salvianolic acid B using a carbon nanotube paste electrode.And the separation process of salvianolic acid B was detected. METHODS: In Britton-Robinson buffer solution of pH(1.81),the square wave stripping voltammetric method was used to determine salvianolic acid B. RESULTS: The proposed method was verified by an established HPLC method,and it was applied to determining salvianolic acid B in eluent of eluting extracts of Radix salvia Miltiorrhiza from SP-207 colunm with ethanol solution,and the results were satisfied. CONCLUSION: A new method for determining salvianolic acid B was developed,and the proposed method would be used as an on-line quality control method for detecting of salvianolic acid B in eluting extracts of Radix salvia Miltiorrhiza in the future.
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Simultaneous determination of zinc, cadmium, tin, lead and copper was studied in 0.2-0.3M hydrochloric acid-methanol by 1.5 grade differential anodic stripping voltammetry. A stick silver base mercurial film electrode was used as a working electrode. The peak potential of Zn, Cd, Sn, Pb and Cu was distinctly separated each other being -1.05V, -0.74V -0.55V, -0.44V and -0.25V vs SCE, respectivly, in the above solvent electrolyte.Calibration curves of Cd, Sn, Pb and Cu in range of 20 to 600 ng/ml and Zn in range of 0.2 to 4 ug/ml showed linear relation. Canned foods could be analyzed, by dilution with the supporting electrolyte after digestion of the samples with mixed acid. The juice samples could be analyzed directly without digestion, by simple 5-2000 times dilution with the supporting electrolyte. Coefficient of variation and recovey was 6.7-8.0% and 91.2-107% respectively.