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1.
Marilene Elisa do Nascimento Patrícia Benedini Martelli Clascídia Aparecida Furtado Adelina P. Santos Luiz Fernando Cappa de Oliveira Honória de Fátima Gorgulho 《Mikrochimica acta》2011,173(3-4):485-493
A new composite electrode is described for anodic stripping voltammetry determination of Pb(II) at trace level in aqueous solution. The electrode is based on the use of multiwalled carbon nanotubes and Amberlite IR-120. The anodic stripping voltammograms depend, to a large extent, on the composition of the modified electrode and the preconcentration conditions. Under optimum conditions, the anodic peak current at around ?0.57 V is linearly related to the concentration of Pb(II) in the range from 9.6?×?10?8 to 1.7?×?10?6 mol L?1 (R?=?0.998). The detection limit is 2.1?×?10?8 mol L?1, and the relative standard deviation (RSD) at 0.24?×?10?6 mol L?1 is 1.7% (n?=?6). The modified electrode was applied to the determination of Pb(II) using the standard addition method; the results showed average relative recoveries of 95% for the samples analysed. Figure
A new composite electrode is described for anodic stripping voltammetry determination of Pb(II) at trace level in aqueous solution. The electrode is based on the use of MWCNT and Amberlite IR-120. The method showed a good linearity for 9.6?×?10?8 - 1.7?×?10?6 mol L?1 and detection limit of 2.1?×?10?8 mol L?1. 相似文献
2.
We have developed a “turn on” model of an electrochemiluminescence (ECL) based assay for lead ions. It is based on the formation of a G-quadruplex from an aptamer labeled with quantum dots (QDs) and placed on an electrode modified with of graphene and gold nanoparticles (AuNPs). A hairpin capture probe was labeled with a thiol group at the 5′-end and with an amino group at the 3′-end. It was then self-assembled on the electrode modified with graphene and AuNPs. In the absence of Pb(II), the amino tag on one end of the hairpin probe is close to the surface of the electrode and therefore unable to interact with the QDs because of steric hindrance. The ECL signal is quite weak in this case. If, however, Pb(II) is added, the stem-loop of the aptamer unfolds to form a G-quadruplex. The amino group at the 3′-end will become exposed and can covalently link to a carboxy group on the surface of the CdTe QDs. This leads to strong ECL. Its intensity increases (“turns on”) with the concentration of Pb(II). Such a “turn-on” method does not suffer from the drawbacks of “turn-off” methods. ECL intensity is linearly related to the concentration of Pb(II) in the 10 p mol·L?1 to 1 n mol·L?1 range, with a 3.8 p mol·L?1 detection limit. The sensor exhibits very low detection limits, good selectivity, satisfying stability, and good repeatability. Figure
A “turn on” model of ECL method was developed based on G-quadruplex of Graphene/AuNPs of aptamer probe by using quantum dots as label. ECL intensity is increased with the increase of Pb2+ concentration. The responsive ECL intensity was linearly related to the Pb2+ concentration in the range of 1.0?×?10?11?~?1.0?×?10?9 mol·L?1, with a detection limit of 3.82?×?10?12 mol·L?1. 相似文献
3.
Gaber Hashem Gaber Ahmed Rosana Badía Laíño Josefa Angela García Calzón Marta Elena Díaz García 《Mikrochimica acta》2014,181(9-10):941-948
We describe the synthesis of ß-cyclodextrin modified magnetic nanoparticles (CD-mNPs) as a material for solid-phase extraction of the cancer biomarker 5-hydroxy-indole-3-acetic acid (5-HIAA) from urine. The CD-mNPs were characterized by TEM, FTIR, and XRD, and the kinetics and adsorption isotherms were studied. The strong interaction between the CD-mNPs and 5-HIAA is the main driving force for recognition and extraction, while the magnetic core of the NPs allows their separation from the sample matrix. Recovery of 5-HIAA from the adsorbent using an adequate solvent regenerated the adsorbent for further use. 5-HIAA was then quantified by fluorometry of its complex with ß-CD. The method works in the 1?×?10?7 to 1?×?10?5 mol L?1 (R2 0.9982–0.9996) concentration range, and the limits of detection (3σ) and quantification (10 σ) of the method are 1.2?×?10?8 mol L?1 and 4.01?×?10?8 mol L?1 5-HIAA, respectively. The recovery of 5-HIAA from urine samples spiked with 5-HIAA in three concentrations (1.4?×?10?6, 4.50?×?10?6 and 1.0?×?10?5 mol L?1) are within 63?±?3 %. Figure
Cyclodextrin functional magnetic nanoparticles as sorbents for separation of 5-hydroxy-3-indole acetic acid and its fluorescence determination after released with methanol. 相似文献
4.
Yazhen Wang 《Mikrochimica acta》2011,172(3-4):419-424
The electrochemistry of uric acid at a gold electrode modified with a self-assembled film of L-cysteine was studied by cyclic voltammetry and differential pulse voltammetry. Compared to the bare gold electrode, uric acid showed better electrochemical response in that the anodic peak current is stronger and the peak potential is negatively shifted by about 100 mV. The effects of experimental conditions on the oxidation of uric acid were tested and a calibration plot was established. The differential pulse response to uric acid is linear in the concentration range from 1.0?×?10?6 to ~?1.0?×?10?4 mol?L?1 (r?=?0.9995) and from 1.0?×?10?4 to ~?5.0?×?10?4 mol?L?1 (r?=?0.9990), the detection limit being 1.0?×?10?7 mol?L?1 (at S/N?=?3). The high sensitivity and good selectivity of the electrode was demonstrated by its practical application to the determination of uric acid in urine samples.
Cyclic voltammograms of UA at the bare electrode (a,b) and the L-Cys/Au electrode (c,d,e) in HAc-NaAc buffer containing different concentrations of UA. (a,c): blank; (b, d): 2.0?×?10?5 mol?L?1; (e) 4.0?×?10?5 mol?L?1. Scan rate: 100 mV?s?1 相似文献
5.
Zhihua Wang Jinshu Li Xiaole Liu Jianming Yang Xiaoquan Lu 《Analytical and bioanalytical chemistry》2013,405(8):2525-2533
A sensitive amperometric sensor for norfloxacin (NF) was introduced. The receptor layer was prepared by molecularly imprinted photopolymerization of acrylamide and trimethylolpropane trimethacrylate on the surface of a gold electrode. The binding mechanism of the molecularly imprinted polymer was explored by ultraviolet (UV) and infrared (IR) spectroscopy. The chemosensor was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance (EI), and scanning electron microscopy (SEM). The electrode prepared by photopolymerization has a better recognition ability to template molecules than that of electropolymerization and NIP. Some parameters affecting sensor response were optimized. Norfloxacin was detected by measurements of an amperometric i–t curve. The linear relationships between current and logarithmic concentration are obtained from 1.0?×?10?9 to 1.0?×?10?3?mol?L?1. The detection limit of the sensor was 1.0?×?10?10?mol?L?1. The proposed method is sensitive, simple, and cheap, and is applied to detect NF in human urine successfully. Figure
Amperometric i-t curves of MIPs electrode 相似文献
6.
Yangyang Chen Lin Xiao Ying Liu Xiaoxi Li Juan Zhang Yongqian Shu 《Mikrochimica acta》2014,181(5-6):615-621
A lipase-based electrochemical biosensor has been fabricated for the quantitative determination of target DNA. It is based on a stem-loop nucleic acid probe labeled with ferrocene containing a butanoate ester that is hydrolyzed by lipase. The other end of the probe DNA is linked, via carboxy groups, to magnetic nanoparticles. The binding of target DNA transforms the hairpin structure of the probe DNA and causes the exposure of ester bonds. This results in the release of electro-active ferrocene after hydrolysis of the ester bonds, and in an observable electrochemical response. The quantity of target DNA in the concentration range between 1?×?10?12 mol·L?1 and 1?×?10?8 mol·L?1 can be determined by measuring the electrochemical current. The method can detect target DNA with rapid response (30 min) and low interference. Figure
A lipase-based electrochemical biosensor has been fabricated for the quantitative determination of target DNA. It is based on a stem-loop nucleic acid probe labeled with ferrocene containing a butanoate ester that is hydrolyzed by lipase. The method can detect target DNA with rapid response (30 min) and low interference. 相似文献
7.
A novel kind of carbon paste electrode (CPE) was prepared by mixing graphite powder, liquid paraffin and the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate. The resulting electrode was used for the simultaneous determination of guanosine and adenosine by differential pulse voltammetry. Compared to a conventional CPE, the oxidation peak currents are largely increased, and the oxidation peak potentials are negatively shifted. The electrochemical responses to guanosine and adenosine were investigated. Under optimized conditions, the calibration curves are linear in the concentration range from 1.0?×?10-6?mol?L-1 to 1.6?×?10-4?mol?L-1 for guanosine, and from 1.0?×?10-6?mol?L-1 to 2.7?×?10-4?mol?L-1 for adenosine at pH 3.5. Substances potentially interfering in the biological matrix do no interfere. The method was successfully applied to detect adenosine and guanosine in human urine without sample treatments. Figure
Cyclic voltammograms on CPE (a) and CILE (b) for 1.0?×?10-4?mol?L-1 adenosine and 1.0?×?10-4?mol?L-1guanosine in a pH 3.5 B-R buffer solution at the scan rate of 100?mV?s-1. Inset was the typical differential pulse voltammograms of 1.0?×?10-4?mol?L-1 adenosine and 1.0?×?10-4?mol?L-1?L guanosine on CILE 相似文献
8.
Li Tian Yongjia Feng Yanjuan Qi Binbin Wang Yinran Chen Xueyan Fu 《Mikrochimica acta》2012,177(1-2):39-45
We report on a novel non-enzymatic sensor for hydrogen peroxide (HP) that is based on a biocomposite made up from chitosan (CS), hemoglobin (Hb), and silver nanoparticles (AgNPs). The AgNPs were prepared in the presence of CS and glucose in an ultrasonic bath, and CS is found to act as a stabilizing agent. They were then combined with Hb and CS to construct a carbon paste biosensor. The resulting electrode gave a well-defined redox couple for Hb, with a formal potential of about ?0.17?V (vs. SCE) at pH?6.86 and exhibited a remarkable electrocatalytic activity for the reduction of HP. The sensor was used to detect HP by flow injection analysis, and a linear response is obtained in the 0.08 to 250?μM concentration range. The detection limit is 0.05?μM (at S/N?=?3). These characteristics, along with its long-term stability make the sensor highly promising for the amperometric determination of HP. Figure
(A) FIA i–t graphs of the different concentrations of H2O2 at CS/Hb/AgNP/CPE in the PBS (pH?6.86). Applied potential: ?0.4?V. (1) 0.8?×?10?6?mol?L?1, (2) 2.4?×?10?6?mol?L?1, (3) 4?×?10?6?mol?L?1 (B) Plot of catalytic peak currents vs. the concentration of H2O2. 相似文献
9.
Linlin Liu Qiang Ma Ziping Liu Yang Li Xingguang Su 《Analytical and bioanalytical chemistry》2014,406(3):879-886
In the present work, a novel flow-injection chemiluminescence method based on CdTe quantum dots (QDs) was developed for the determination of nitrite. Weak chemiluminescence (CL) signals were observed from a CdTe QDs–H2O2 system under basic conditions. The addition of a trace amount of hemoglobin (Hb) caused the CL from the CdTe QDs–H2O2 system to increase substantially. In the presence of nitrite, the ferrous Hb reacted with the nitrate to form ferric Hb and NO. The NO then bound to ferrous Hb to generate iron nitrosyl Hb. As a result, the CL signal from the CdTe QDs–H2O2–Hb system was quenched. Thus, a flow-injection CL analytical system for the determination of trace nitrite was established. Under optimum conditions, there was a good linear relationship between CL intensity and the concentration of nitrite in the range 1.0?×?10?9 to 8.0?×?10?7 mol L?1 (R 2?=?0.9957). The limit of detection for nitrite using this system was 3.0?×?10?10 mol L?1 (S/N?=?3). This method was successfully applied to detect nitrite in water samples. Figure
The scheme of the mechanism of the CL system 相似文献
10.
Nickel oxide nanoparticles (NiO-NPs) were electrodeposited on a film of multi-walled carbon nanotubes to improve the electro-oxidation of nitric oxide (NO). The resulting sensor film exhibits excellent electrocatalytic activity towards NO and was used for the construction of an amperometric sensor for NO that was applied to monitoring the release of NO from sodium nitroprusside in rat kidney. Key operational parameters such as the conditions for deposition, kind of electrolyte and pH value were optimized. The nano-structured sensor possesses numerous active sites for oxidation of NO and thus exhibits good performance including wide linearity, simple operation, and good stability. The response to NO is linear in the concentration range from 80.0?nmol·L?1 to 0.117?mmol·L?1, the limit of detection is 20.0 n mol·L?1. The sensor was developed for real-time monitoring of NO. Figure
Amperometric response of the sensor to NO released from rat kidney. 相似文献
11.
A novel enzyme-free electrochemical sensor for H2O2 was fabricated by modifying an indium tin oxide (ITO) support with (3-aminopropyl) trimethoxysilane to yield an interface for the assembly of colloidal gold. Gold nanoparticles (AuNPs) were then immobilized on the substrate via self-assembly. Atomic force microscopy showed the presence of a monolayer of well-dispersed AuNPs with an average size of ~4 nm. The electrochemical behavior of the resultant AuNP/ITO-modified electrode and its response to hydrogen peroxide were studied by cyclic voltammetry. This non-enzymatic and mediator-free electrode exhibits a linear response in the range from 3.0?×?10?5 M to 1.0?×?10?3 M (M?=?mol?·?L?1) with a correlation coefficient of 0.999. The limit of detection is as low as 10 nM (for S/N?=?3). The sensor is stable, gives well reproducible results, and is deemed to represent a promising tool for electrochemical sensing. Figure
AuNPs/ITO modified electrode prepared by self-assembly method exhibit good electrocatalytic activity towards enzyme-free detection H2O2. The linear range of typical electrode is between 3.0?×?10?5 M and 1.0?×?10?3 M with a correlation coefficient of 0.999 and the limit detection is down to 1.0?×?10?8 M. 相似文献
12.
We have synthesized the near-infrared water-soluble conjugated polymer poly[2,5-di(propyloxysulfonate)-1,4-phenylene-ethynylene-9,10-anthrylene (referred to as PPEASO3). Its fluorescence (at wavelengths between 650 and 800?nm following photoexcitation at 550?nm) is efficiently quenched by Cu(II) ions, while other physiologically relevant metal ions do not cause significant quenching at the same concentrations. Under optimum conditions, fluorescence intensity is inversely proportional to the concentration of Cu (II). The calibration curve displays two linear regions over the range of 0–3.2?×?10?7 mol L?1 and 3.2?×?10?7 mol L?1 to 1.0?×?10?4 mol L?1 of Cu(II), respectively. The long-wavelength excitation and emission can substantially reduce interferences by the autofluorescence and light scattering of biological matter under UV excitation. The method was successfully applied to the determination of Cu(II) in synthetic and tea samples. Figure
Highly sensitive fluorescent sensor with low background interference was successfully applied to the determination of Cu (II) in synthetic and real samples, based on amplified fluorescence quenching of a water-soluble NIR emitting conjugated polymer. 相似文献
13.
Li Tian Boxun Zhang Ding Sun Ruizhan Chen Binbin Wang Tianjiao Li 《Mikrochimica acta》2014,181(5-6):589-595
We have fabricated, in a single step, carbon ceramic electrodes modified with a poly(acridine orange) film containing reduced graphene oxide. They display electrocatalytic activity to ascorbic acid (AA) and uric acid (UA) at pH 4.5. The anodic peak potentials of AA and UA are separated by 276 mV so that they can be well resolved in cyclic voltammetry. UA and AA were simultaneously determined in a mixture at working potentials of 170 and 400 mV, respectively. Under optimized conditions, the calibration curves for AA and UA cover the 0.8–5,000 μM and 0.6–900 μM concentration range, respectively, while detection limits are 0.3 μM and 0.2 μM. The electrode was applied to determine AA and UA in urine samples. Figure
DPV curves of RGO–PAO/CCE in the phosphate buffer solution (pH 4.5) containing 5.0?×?10?5 mol L?1 AA with different concentration of UA (a?→?f: 0, 1, 3, 5, 7, 9?×?10?6 mol L?1) 相似文献
14.
《Analytical letters》2012,45(7):1321-1332
Abstract A novel amperometric nitric oxide (NO) sensor based on a glassy carbon electrode modified with thionine and Nafion films has been developed. The oxidation peak current of NO increased significantly at the poly(thionine)/Nafion‐modified glassy carbon electrode (GCE), which can be used for the detection of NO. The oxidation peak current was linear with the concentration of nitric oxide over the range from 3.6×10?7 to 6.8×10?5 mol · L?1, and the detection limit was 7.2×10?8 mol · L?1. This nitric oxide sensor showed high selectivity to nitric oxide determination, and some potential interference could be eliminated effectively. The nitric oxide sensor has been applied to monitor NO release from rat kidney stimulated by L‐arginine. The results indicated the applicability of the NO sensor to biomedical samples. 相似文献
15.
Li Lin Hongchang Gao Dan Lin MiaoMiao Gao Min Xiao Shulin Yang Xiaokun Li 《Chromatographia》2010,72(5-6):447-452
Liquid chromatography with electrochemical detection (LC-ED), coupled with in vivo microdialysis sampling, has been used for analysis of thiols. An acetylene black–dihexadecyl hydrogen phosphate (AB–DHP) composite film-modified electrode was used as working electrode. The AB–DHP-modified electrode enabled efficient electrocatalytic oxidation of l-cysteine (l-Cys) and glutathione (GSH) with relatively high sensitivity, stability, and longevity. The peak currents of l-Cys and GSH were linear in the concentrations ranges 2.0 × 10?7–2.0 × 10?4 and 3.0 × 10?7–5.0 × 10?4 mol L?1, respectively, with calculated detection limits (S/N = 3) of 1.0 × 10?7 and 2.0 × 10?7 mol L?1, respectively. The method has been successfully used to measure the amounts of l-Cys and GSH in striatal microdialysate of freely moving rats. 相似文献
16.
A novel glucose biosensor is presented as that based on a glassy carbon electrode modified with hollow gold nanoparticles (HGNs) and glucose oxidase. The sensor exhibits a better differential pulse voltammetric response towards glucose than the one based on conventional gold nanoparticles of the same size. This is attributed to the good biological conductivity and biocompatibility of HGNs. Under the optimal conditions, the sensor displays a linear range from 2.0?×?10?6 to 4.6?×?10?5?M of glucose, with a detection limit of 1.6?×?10?6?M (S/N?=?3). Good reproducibility, stability and no interference make this biosensor applicable to the determination of glucose in samples such as sports drinks. Figure
A novel glucose biosensor was prepared based on glucose oxidase, hollow gold nanoparticles and chitosan modified glassy carbon electrode. The electrode showed a good response for the glucose. The sensor has been verified by the determination of glucose in sport drink 相似文献
17.
We have prepared a glassy carbon electrode modified with poly-2,6-pyridinedicarboxylic acid and with magnetic Fe3O4 nanoparticles. This modification enhances the effective surface area and the electrocatalytic oxidation of nicotinamide adenine dinucleotide (NADH) in addition to providing positively charged groups for electrostatic assembly of the phosphate group of NADH. The modified electrode responds linearly to NADH in the range from 5?×?10?8 to 2.5?×?10?5?M and gives a lower detection limit of 1?×?10?8?M. It displays satisfactory selectivity and reproducibility. The sensor was applied to rapid screening of plant extracts for their antioxidant properties. Figure
Poly-2,6-pyridinedicarboxylic acid (PDC) was fabricated by electropolymerizing 2,6-pyridinedicarboxylic acid with cyclic voltammetry (CV) on the glassy carbon electrode (GCE) surface. The magnetic Fe3O4 nanoparticles treated with aminopropyltriethoxysilane (APTS) modified on the PDC/GCE to form APTS-Fe3O4/PDC composite film. The APTS-Fe3O4/PDC film had enhanced the effective electrode surface area and provided positively charged groups for electrostatic assembly of phosphate group of NADH. 相似文献
18.
Sylwia Smarzewska Dariusz Guziejewski Monika Skowron Slawomira Skrzypek Witold Ciesielski 《Central European Journal of Chemistry》2014,12(12):1239-1245
The use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) for the analytical determination of ambazone in urine samples and pharmaceutical formulations is described. A single reduction peak in Britton-Robinson buffer at pH 4.0 was detected at about ?1.4 V versus Ag/AgCl. Mechanistic studies have shown that the compound can act as an electrocatalyst. The method was validated. The analytical curve was linear in the concentration range from 1.0×10?9 to 1.0×10?7 mol L?1. The detection and quantification limits were found to be 3.0×10?10 mol L?1 and 1.0×10?9 mol L?1, respectively. The proposed method was successfully applied to ambazone determination in real samples. 相似文献
19.
Caroline Perez Fábio Ruiz Simões Lúcia Codognoto 《Journal of Solid State Electrochemistry》2016,20(9):2471-2478
In this work, a simple method for electroanalytical determination of 17α-ethinylestradiol (EE2) hormone in natural waters was developed using a boron-doped diamond electrode (BDD). The analyses were performed using square wave voltammetry and the parameters were optimized. The results showed a well-defined irreversible oxidation peak (BR buffer 0.1 mol L?1, pH 8.0) at +0.65 V (vs. Ag/AgCl). The voltammetric results showed also that the oxidation process is controlled by adsorption of species and indicated that there are two electrons involved. The obtained analytical curves for 17α-ethinylestradiol presented good linearity in the concentration range 9.9?×?10?7 to 5.2?×?10?6 mol L?1 in utlrapure water and 7.9?×?10?7 to 5.2?×?10?6 mol L?1 in natural water samples (supply dam). Detection limits (DL) obtained were between 2.4?×?10?7 and 7.5?×?10?7 mol L?1 and quantification limits (QL) between 7.9?×?10?7 and 2.5?×?10?6 mol L?1. The recovery experiments showed values between 86 and 114 % for spiked samples thus indicating the applicability of the electroanalytical methodology to quantify 17α-ethinylestradiol directly in natural water of supply Dam (Billings Dam in Diadema-SP. Brazil), without any preconcentration or derivatization. 相似文献
20.
The reactions of 3(5)-(4-methoxyphenyl)-5(3)-phenyl-1H-pyrazole (L 1 ) with nitric acid and 5-(4-benzyloxyphenyl)-3-(furan-2-yl)-1H-pyrazole(L 2 ) with hydrochloric acid produced [HL 1 · NO3] (Salt-1) and [HL 2 · Cl] (Salt-2). The structures of Salt-1 and Salt-2 were determined by single crystal X-diffraction. In Salt-1, HL 1 showed [2 + 2] binding of NO3 ? ions in the solid state to form dimer architecture with R 1 2 (4) and R 4 4 (14) graph sets. An anion directed one-dimensional anion-assisted helical chain with active participation of the chloride ion and protonated pyrazole via N–H···Cl hydrogen bonding in Salt-2. In addition, the protonated HL 2 molecules interacted with each other through weak C–H···π interactions resulting in the formation of another one-dimensional helical chain. 相似文献