共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Multiwalled carbon nanotubes were used as solid phase extraction (SPE) adsorbent for the determination of four chloroacetanilide herbicides (alachlor, acetochlor, metolachlor and butachlor) in water. The primary factors that influence the efficiency of the SPE performance, such as the amount of the adsorbent, the eluent solvent, the pH and the sample volume, were investigated and optimized. Under optimized conditions, the recoveries of the four herbicides at three spike levels were in the range 76.7–104.4%, and the RSDs ranged from 2.5–12.7%. Good linearity was obtained for the pesticides in the concentration range 0.0025–2.5 mg L?1, and the detection limits were 0.01–0.03 μg L?1 at signal-to-noise ratios of 3:1. The method was successfully applied to the determination of these analytes in tap water and river water. 相似文献
3.
An amperometric sensor for L-Cys is described which consists of a glassy carbon electrode (GCE) that was modified with reduced graphene oxide placed in a Nafion film and decorated with palladium nanoparticles (PdNPs). The film was synthesized by a hydrothermal method. The PdNPs have an average diameter of about 10 nm and a spherical shape. The modified GCE gives a linear electro-oxidative response to L-Cys (typically at +0.6 V vs. SCE) within the 0.5 to 10 μM concentration range. Other figures of merit include a response time of less than 2 s, a 0.15 μM lower detection limit (at signal to noise ratio of 3), and an analytical sensitivity of 1.30 μA·μM?1·cm?2. The sensor displays selectivity over ascorbic acid, uric acid, dopamine, hydrogen peroxide, urea, and glucose. The modified GCE was applied to the determination of L-Cys in human urine samples and gave excellent recoveries. 相似文献
4.
5.
Behzad Haghighi Hassan Hamidi Somayyeh Bozorgzadeh 《Analytical and bioanalytical chemistry》2010,398(3):1411-1416
A glassy carbon electrode modified with palladium nanoparticles decorated multiwalled carbon nanotubes (GCE/nanoPd-MWCNTs)
was fabricated. Incorporation of palladium nanoparticles onto the carbon nantube surface by thermal decomposition of palladium
acetate led to the fabrication of a sensor with a significant decrease in hydrazine electrooxidation potential. The sensor
exhibited low detection limits, high sensitivity and selectivity, rapid response, and good stability toward hydrazine detection. 相似文献
6.
This study presents a method for the selective determination of Hg(II) using electromembrane extraction (EME), followed by square wave anodic stripping voltammetry (SWASV), using a gold nanoparticle-modified glassy carbon electrode, (AuNP/GCE). By applying an electrical potential of typically 60 V for 12 min through a thin supported liquid membrane (1-octanol), Hg(II) ions are extracted from a donor phase (i.e., the sample solution) to an acidic acceptor solution (15 μL) placed in the lumen of a hollow fiber. The influences of experimental parameters during EME were optimized using face-centered central composite design. The calibration plot, established at a working voltage of 0.55 V (vs. Ag/AgCl), extends from 0.2 to 10 μg.L?1 of Hg(II). The limit of detection, at a signal to noise ratio of 3, is 0.01 μg.L?1 and the relative standard deviations (for 5 replicate determinations at 3 concentration levels) are between 7.5 and 8.7 %. The method was successfully applied to the determination of Hg(II) in spiked real water samples to give recoveries ranging from 89 to 97 %. The results were validated by cold vapor atomic absorption spectroscopy. 相似文献
7.
Lemma Teshome Tufa Khalid Siraj Tesfaye Refera Soreta 《Russian Journal of Electrochemistry》2013,49(1):59-66
Electrochemical application of bismuth film modified glassy carbon electrode was studied with the objective of lead detection. Bismuth film on glassy carbon substrate was formed in a plating solution of 2 mmol/L Bi(NO3)3, in 1 mol/L HCl at ?1.1 V (vs. Ag/AgCl) for 300 s. Lead was detected by differential pulse anodic voltammetry in acetate buffer of pH 5.0 in the concentration range of 7.5 nmol/L to 12.5 μmol/L. Factors influencing the anodic stripping performance, including deposition time, solution pH, Bi(III) concentration, potential, pulse amplitude, pulse width, have been optimized. Three linear calibration plots in the range 7.5 nmol/L to 0.1 μmol/L, 0.25 to 1 μmol/L, 2.5 to 12.5 μmol/L with regression coefficients of 0.991, 0.986 and 0.978 respectively were obtained. The theoretical detection limit equivalent to three times standard deviation for 7.5 nmol/L lead (n = 5) was calculated to be 5.25 nmol/L utilizing a 5 min deposition time and sensitivity 83.97 A L/mol. The sensitivity and detection limit of the method was compared with reported voltammetric methods for detection of lead and the result obtained was found to be promising for determination of lead. 相似文献
8.
Voltammetric determination of tinidazole using a glassy carbon electrode modified with single-wall carbon nanotubes. 总被引:1,自引:0,他引:1
Chunhai Yang 《Analytical sciences》2004,20(5):821-824
An electrochemical method based on a single-wall carbon nanotubes (SWNTs) film-coated glassy carbon electrode (GCE) was described for the determination of tinidazole. In a 0.1 M Britton-Robinson buffer with a pH of 10.0, tinidazole yields a very sensitive and well-defined reduction peak at -0.78 V (vs. SCE) on a SWNTs-modified GCE. Compared with that on a bare GCE, the reduction peak of tinidazole increases significantly on the modified GCE. Thus, all of the experimental parameters were optimized and a sensitive voltammetric method is proposed for tinidazole determination. It is found that the reduction peak current is proportional to the concentration of tinidazole over the range from 5 x 10(-8) to 4 x 10(-5) M, and that the detection limit is 1 x 10(-8) M at 3 min open-circuit accumulation. This new analysis method was demonstrated with tinidazole drugs. 相似文献
9.
10.
A glassy carbon electrode (GCE) was modified with silicon carbide nanoparticles and used to investigate the electrochemistry of the drug nimesulide via voltammetry and chronoamperometry. The structure of the modified electrode was studied by field emission scanning electron microscopy. Nimesulide undergoes electroreduction at pH 2 at a potential that is shifted from ?526 mV (at the bare GCE) to ?387 mV at the modified electrode. Simultaneously, sensitivity is increased by a factor of 5.8. The charge transfer coefficient, diffusion coefficient, standard heterogeneous rate constant and catalytic reaction rate constant were determined. A plot potential vs. pH revealed a voltammetric pKa value of about 6.5–7.0. The differential pulse voltammetric calibration plot for nimesulide is linear in 0.09–8.7 μM concentration range, and the detection limit and sensitivity are 30 nM and 512 nA.μM?1, respectively. The modified electrode was applied to the determination of nimesulide in acidic solution and human blood serum samples without further pretreatment. The recoveries, as determined by the standard addition method, range from 95.7 to 98.7%, with an RSD of around 1.6%. Figure
(A) CVs of SiC-NPs/GC modified electrode at scan rate 0.1 V.s-1 in pH 2.0 PBS solutions in the absence (c) and the presence of 8.0 μM nimesulide (d). (a) and (b) as (c) and (d), respectively at bare GC electrode. (B) DPVs at voltage step 0.008 V, sweep rate 0.02 V.s?1 and pulse amplitude 0.05 V in pH 2.0 PBS solutions in the absence (c) and the presence of 8.0 μM nimesulide (d). (a) and (b) as (c) and (d) respectively at bare GC electrode. 相似文献
11.
This study reports a detailed analysis of an electrode material containing poly(phenolphthalein), carbon nanotubes and gold nanoparticles which shows superior catalytic effect towards to hydrazine oxidation in Britton–Robinson buffer (pH 10.0). Glassy carbon electrode was modified by electropolymerization of phenolphthalein (PP) monomer (poly(PP)/GCE) and the multiwalled carbon nanotubes (MWCNTs) was dropped on the surface. This modified surface was electrodeposited with gold nanoparticles (AuNPs/CNT/poly(PP)/GCE). The fabricated electrode was analysed the determination of hydrazine using cyclic voltammetry, linear sweep voltammetry and amperometry. The peak potential of hydrazine oxidation on bare GCE, poly(PP)/GCE, CNT/GCE, CNT/poly(PP)/GCE, and AuNPs/CNT/poly(PP)/GCE were observed at 596 mV, 342 mV, 320 mV, 313 mV, and 27 mV, respectively. A shift in the overpotential to more negative direction and an enhancement in the peak current indicated that the AuNPs/CNT/poly(PP)/GC electrode presented an efficient electrocatalytic activity toward oxidation of hydrazine. Modified electrodes were characterized with High-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Amperometric current responses in the low hydrazine concentration range of 0.25–13 µM at the AuNPs/CNT/poly(PP)/GCE. The limit of detection (LOD) value was obtained to be 0.083 µM. A modified electrode was applied to naturel samples for hydrazine determination. 相似文献
12.
We have developed a method for the determination of the three catecholamines (CAs) epinephrine (EP), norepinephrine (NE), and dopamine (DA) at sub-nanomolar levels. It is found that the luminescence of the complexes formed between the CAs and Tb3+ ion is strongly enhanced in the presence of colloidal silver nanoparticles (Ag-NPs). The Ag-NPs cause a transfer of the resonance energy to the fluorophores through the interaction of the excited-state fluorophores and surface plasmon electrons in the Ag-NPs. Under the optimized condition, the luminescence intensity of the system is linearly related to the concentration of the CAs. Linearity is observed in the concentration ranges of 2.5–110?nM for EP, 2.8–240?nM for NE, and 2.4–140?nM for DA, with limits of detection as low as 0.25?nM, 0.64?nM and 0.42?nM, respectively. Relative standard deviations were determined at 10?nM concentrations (for n?=?10) and gave values of 0.98%, 1.05% and 0.96% for EP, NE and DA, respectively. Catecholamines were successfully determined in pharmaceutical preparations, and successful recovery experiments are demonstrated for urine and serum samples. Figure
Schematic presentation of Ag NP-enhanced luminescence of Tb3+-CA complex. (A) Luminescence intensity at 545 nm of Tb3+-EP complex is lower than that of (B) Tb3+-EP-Ag NP system when both are excited at the wavelength of 279 nm. 相似文献
13.
We report on a sensitive electrochemical sensor for dopamine (DA) based on a glassy carbon electrode that was modified with a nanocomposite containing electrochemically reduced graphene oxide (RGO) and palladium nanoparticles (Pd-NPs). The composite was characterized by scanning electron microscopy, energy dispersive spectroscopy, and electrochemical impendence spectroscopy. The electrode can oxidize DA at lower potential (234 mV vs Ag/AgCl) than electrodes modified with RGO or Pd-NPs only. The response of the sensor to DA is linear in the 1–150 μM concentration range, and the detection limit is 0.233 μM. The sensor was applied to the determination of DA in commercial DA injection solutions. Figure
Schematic representation showing the oxidation of DA at RGO-Pd-NPs composite electrode. 相似文献
14.
Electrochemical determination of malachite green using a multi-wall carbon nanotube modified glassy carbon electrode 总被引:1,自引:0,他引:1
A multi-wall carbon nanotube (MWNT) film-modified electrode is described for the determination of malachite green (MG). The
electrochemical profile of MG was examined using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), suggesting
that the MWNT film facilitates the electron transfer of MG in terms of a potential shift and then significantly enhances the
oxidation peak current of MG. The experimental parameters, such as supporting electrolyte, thickness of MWNT film, scan rate
and accumulation time, were optimized. Consequently, a sensitive and convenient electrochemical method is proposed for the
determination of MG. The oxidation peak current is proportional to the concentration of MG over the range from 5.0 × 10−8 to 8.0 × 10−6 mol L−1 obeying the following equation: ip = 0.09 + 1.19 × 107 C (r = 0.995, ip in μA, C in mol L−1). The detection limit is 6.0 × 10−9 mol L−1 (signal to noise = 3) after 5 min of accumulation. Moreover, this method possesses good reproducibility (RSD is 5.6%, n =
8) as well as long-term stability. Finally, the new method was employed to determine MG in fish samples.
Correspondence: W. Huang, Department of Chemistry, Hubei Institute for Nationalities, Enshi 445000, P.R. China 相似文献
16.
17.
18.
19.
In this work, an electrochemical sensor 1-phenyl-3-methyl-4-(2-furoyl)-5-pyrazolone/multiwalled carbon nanotubes/glassy carbon
electrode (GCE) was prepared for the determination of xanthine (XN) in the presence of an excess of uric acid. Cyclic voltammetry
and differential pulse voltammetry were used to characterize the electrode. The oxidation of XN occurred in a well-defined
peak having E
p 0.73 V in phosphate buffer solution of pH 6.0. Compared with the bare GCE, the electrochemical sensor greatly enhanced the
oxidation signal of XN with negative shift in peak potential about 110 mV. Based on this, a sensitive, rapid, and convenient
electrochemical method for the determination of XN has been proposed. Under the optimized conditions, the oxidation peak current
of XN was found to be proportional to its concentration in the range of 0.3~50 μM with a detection limit of 0.08 μM. The analytical
utility of the proposed method was demonstrated by the direct assay of XN in urine samples and was found to be promising at
our preliminary experiments. 相似文献
20.
In this paper, a novel poly(aminosulfonic acid) modified glassy carbon electrode (PASA/GCE) for the determination of Sudan II was fabricated through electrochemical polymerizat ion. The electrochemical behavior of Sudan II at the modified electrode was studied by cyclic voltammetry. Results show that the modified electrode exhibits excellent electrocatalytic activity toward the electrochemical redox reaction of Sudan II. Under optimal experimental conditions, the oxidation peak current is linearly proportional to the concentration of Sudan II in the ranges of 4.0 × 10?8 to 1.0 × 10?6 mol L?1 and 1.0 × 10?6 to 1.2 × 10?5 mol L?1. The linear regression equations are i pa(A) = 2.87c + 3.74 × 10?6, r = 0.9977 and i pa(A) = 0.78c + 6.11 × 10?6, r = 0.9982, respectively, and the detection limit is 4.0 × 10?9 mol L?1. The novel method shows good recovery, reproducibility and sensitivity for the voltammetric determination of Sudan II in food samples. 相似文献