共查询到20条相似文献,搜索用时 31 毫秒
1.
《Analytical letters》2012,45(15):2691-2700
Abstract The voltammetric behaviour of minocycline at a water/nitrobenzene interface has been studied by normal, semi-differential and semi-integral cyclic voltammetry. The semi-differential cyclic voltammetry can be used as a rapid, simple method for determination of the antibiotic minocycline in the range of 5–200 ug/ml and the relative standard deviation is within 3%. Drug samples were analyzed and satisfactory results were found as compared with US Pharmacopoeia method. 相似文献
2.
O. M. Petrukhin M. V. Kostitsyna T. G. Dzherayan E. V. Shipulo E. V. Vladimirova A. A. Dunaeva 《Journal of Analytical Chemistry》2009,64(9):951-957
The complexation of aminoglycoside antibiotics with metal cations was proposed as a derivatization method for the further
determination of the complex obtained by potentiometry with ion-selective electrodes (ISE), voltammetry at the interface between two immiscible electrolyte solutions (ITIES), and spectrophotometry. It was shown by the spectrophotometric method that gentamicin formed a 1: 1 complex with copper(II).
For the potentiometric determination of gentamicin, we obtained ionophores that were ion associates formed by the gentamicin
complex of copper(II) and tetraphenylborate derivatives as counterions. The transfer of the gentamicin complex of copper(II)
was studied voltammetrically at the ITIES. The results obtained indicate that l antibiotic gentamicin can be directly determined
as a complex with copper(II) by potentiometric, voltammetric, and spectrophotometric methods. 相似文献
3.
The electrochemical behavior of paracetamol in 0.1 M acetate buffer solution (pH 4.6) was investigated at a traditional carbon
paste electrode (TCPE) and a carbon ionic liquid electrode (CILE) fabricated by replacing nonconductive organic binders with
a conductive hydrophobic room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6). The results showed that the CILE exhibited better reversibility for the electrochemical redox of paracetamol. The oxidation
potential of paracetamol at the CILE is +0.462 V, which is approximately 232 mV lower than that at the TCPE; the oxidation
peak current response is nine times higher than that at the TCPE. The differential pulse voltammetric determination of paracetamol
at the CILE was established based on this behavior. After optimizing several important parameters controlling the performance
of paracetamol at the CILE, the oxidation peak current versus paracetamol concentration at the CILE showed linearity in the
range from 1.0 μM to 2.0 mM (R
2
= 0.9992) with a detection limit of 0.3 μM (S/N = 3). The method has been applied to the determination of paracetamol in
tablets and urine samples and the average recovery of paracetamol was 98.5% and 99.3%, respectively. The proposed CILE showed
good sensitivity and reproducible response without influence of interferents commonly existing in pharmaceutical and urine
samples.
Figure CV curves of paracetamol illustrate the enhanced electrochemical behavior of paracetamol at the CILE (b), which forms the basis for the differential pulse voltammetric determination of paracetamol 相似文献
4.
5.
The quantitative determination of boldine alkaloid in boldo leaf extracts by employing cyclic voltammetry, at a liquid/liquid interface as well as the validation of this methodology against the reference method, high performance liquid chromatography (HPLC), are reported in the present paper. The voltammetric analysis was performed successfully and economically using two kinds of liquid/liquid interfaces: water/1,2-dicholoroethane and water/PVC (polyvinyl chloride)-gelled 1,2-dichloroethane. Linear calibration curves in the concentration range of 1.04 × 10−5 mol L−1 to 5.19 × 10−4 mol L−1 were obtained with a detection limit equal to (6.1 ± 0.7) × 10−5 mol L−1 and the quantitative determination of this alkaloid, in complex matrixes such as boldo leaf extracts, by the electrochemical technique proposed was found to be equal to the values obtained using the standard HPLC method. The validation analysis of this methodology against HPLC demonstrated that accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ), specificity and precision are acceptable. The electroanalytical technique proposed is economical and selective, involves simple equipment and can be applied for the quantitative determination of boldine alkaloid in complex matrixes such as leaf extracts without special drug separation. Moreover, cyclic voltammetry (CV) experiments applied at the liquid/liquid interface under different experimental conditions allowed us to study the transfer mechanism of boldine, and determine a value of pKaw = 6.90 for protonated boldine, from the variation of voltammetric peak current with pH. 相似文献
6.
《Analytical letters》2012,45(23-24):2307-2315
Abstract Trazodone, a triazolopyridine derivative with antidepressant activity, is irreversibly oxidized in two steps in a large range of scan rates. The first peak shows a linear dependence on trazodone concentration. This behaviour is used for analytical purposes in determining trazodone concentrations in commercial preparations. An original alternative gas-liquid chromatographic method is also developed. Comparison of the chromatographic with voltammetric methods shows that a) both are sensitive enough to be applied to single tablet assays; b) the major advantage of the voltammetric method for analytical purposes lies in the rapid determination of the trazodone content in tablets. Preparation of the samples is easy and no extraction procedure is required. 相似文献
7.
Krzysztof Stolarczyk Renata Bilewicz Anna Skwierawska Jan F. Biernat 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):173-179
Properties of monolayers of azocrown compound self-assembled on gold substrates were studied using voltammetry and scanning tunneling microscopy. The surface concentrations of this compound in monolayers were determined from the area of the voltammetric reduction peaks. The area per one molecule estimated from voltammetry experiments is 0.65 nm2. This value was comparable with the limiting molecular area of the compound in the Langmuir–Blodgett film at the air–water interface. We also observed the presence of gold clusters and other gold structures by STM when a gold electrode modified with azocrown compound was dipped into the tetrachloroaurate solution. Even better spectra of clusters were obtained following one voltammetric scan in the range 0.5 to ?0.6 V. After more cycles or if we condition the electrode at 0.4 V the clusters aggregate into wires. 相似文献
8.
In this study for the first time a novel erbium(III) voltammetric ion‐selective nanocomposite carbon‐paste electrode was introduced based on the concept of ion transfer at the interface between two immiscible electrolyte solutions. N′‐(2‐hydroxy‐1,2‐diphenylethylidene) benzohydrazide (HDB) was used as a selective ionophore in the composition of the carbon paste. The ionophore facilitates transfer of Er(III) from the aqueous solution to the room temperature ionic liquid (RTIL) phase after reduction of the redox probe to maintain charge neutrality. The plot of the peak potential versus the logarithm of the concentration exhibits a Nernstian response (19.9±0.2 mV decade?1) toward Er(III) in the range of 7.5×10?7–1.0×10?1 mol L?1 with detection limit of 5.0×10?7 mol L?1. The proposed sensor shows a fast response time of about 5 s. 相似文献
9.
O. Pietraszkiewicz M. Pietraszkiewicz H. Radecka J. Radecki 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):129-134
Lipophilic polyamines 1 and 2 form stable monolayers at the air–water interface. The shapes of the isotherms show a strong pH-dependence due to different stages of polyamine protonation. For all isomers of dihydroxybenzene the strong interaction with 1 and 2 can be observed at pH 4, 6, and 8. Polyamines 1and 2 in the PVC liquid membrane act as the sensory element of the potentiometric sensor for selective determination of catechol in the presence of other isomers of dihydroxybenzenes. 相似文献
10.
《Journal of Coordination Chemistry》2012,65(23):4217-4229
This article presents the synthesis, physico-chemical, in particular voltammetric, characteristics of two iron(III) complexes with pyridoxal aminoguanidine (PLAG), [Fe(PLAG)Cl2(H2O)]Cl (1) and [Fe(PLAG)2](NO3)3 (2). As expected, the zwitterion of the chelate ligand is coordinated tridentate through oxygen of phenol and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In both complexes, Fe(III) is distorted octahedral. [Fe(PLAG)2](NO3)3 (2) is the first bis(ligand) complex with this ligand. Cyclic voltammetric characteristics of the ligand and complexes were studied in DMF in the presence of TBAP or LiCl as supporting electrolytes. The complexes are unstable in this solvent, especially in the presence of an excess of chloride, thus forming several reducible species whose stabilities and behaviors were characterized. 相似文献
11.
《Analytical letters》2012,45(4):213-220
Abstract The voltammetric behaviour of iodide ions, K4 Fe(CN)6, K3 Fe(CN)6, quinone, hydroquinone, p-phenylenediamine and p-toluidine was studied with graphite impregnated silicone rubber electrodes. The electrode enables us to carry out the quantitative analysis of these compounds. The peak height of the voltammetric curves is proportional to the concentration. Data on the reproducibility of measured values are given. 相似文献
12.
《Analytical letters》2012,45(4):257-265
Abstract It has been found that two chronopotentiometric oxidation waves result for hydroquinone using a platinum electrode in the pH range 8.0 to 8.6. This phenomenon is ascribed to the effect of platinum oxide on the reversibility of the various steps in the oxidation mechanism. EPR, cyclic voltammetric and chronopotentiometric evidence is presented. 相似文献
13.
Kentaro Tashiro Takuzo Aida 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):215-217
Spectroscopic and voltammetric analyses on inclusion complexes of a fullerene such as C60 with a cyclic dimer of a free-base porphyrin (1-M; M = 2H) and its metal complexes (M = Co, Ag, and Zn) showed that a charge-transfer interaction is partly responsible for the complexation. 相似文献
14.
《Journal of Coordination Chemistry》2012,65(14):2425-2434
Mononuclear complexes of 3-methylpyrazole with general formulas (3-Mepz)4CuCl2 (1), (3-Mepz)4CoCl2 (2), (3-Mepz)2PdCl2 (3), and (3-Mepz)2ZnCl2 (4) were prepared by reaction of the corresponding MCl2 salt (M?=?Cu, Co, Pd, and Zn) with 3-methylpyrazole in appropriate amounts using acetonitrile as solvent at ambient temperature. The X-ray crystal structure determination reveals that 1 and 2 possess octahedral geometry, while 3 and 4 are square planar and tetrahedral, respectively. All the synthesized compounds have the MCl2 fragment, thus making the synthesized compounds attractive synthons for further transformation. The cyclic voltammograms of the synthesized complexes were obtained and the voltammetric signatures of 1, 2, and 4 showed a single irreversible pH-dependent cathodic peak, while 3 has two reversible cathodic peaks. Involvement of protons accompanying the electron transfer processes was ascertained from differential pulse voltammetric results, indicating peak potential shift as a function of pH. 相似文献
15.
Chaumont A. Galand N. Schurhammer R. Vayssière P. Wipff G. 《Russian Chemical Bulletin》2004,53(7):1459-1465
The behavior of ion complexes at the water—supercritical carbon dioxide interface was considered by molecular dynamics simulations. The following complexes were studied: Cs+calix[4]crown-6, K+222 cryptate with chloride or dicarbollide (CCD–) counterions, the Sr2+18C6 complex with the picrate (Pic–) or perfluorooctanoate (PFO–) counterions, and the Cl–Tet
4+ complex with chloride counterions (Tet
4+ is a tetrahedral tetraammonium cation). The simulations demonstrate the analogy between aqueous interfaces with organic immiscible liquids and the CO2 phase. Water and supercritical CO2 are poorly miscible and form an interface. Most of the complexes are accumulated at the interface, instead of diffusing into the organic phase in which they should be more soluble. In addition, marked counterion effects are observed. The CCD–, Pic–, and PFO– anions are surface active and are concentrated at the interface, but show different relationships with the complexes. The formation of ion pairs is precluded by the very hydrophobic CCD– anions, which promote the extraction of cryptates as separated ion pairs to the CO2 phase. Conversely, the extraction of the Sr2+ ions with 18C6 proceeds via a co-complexation mechanism, including the formation of the Sr18C6(PFO)2, complex having a CO2 affinity. The mechanism of assisted ion transfer to the CO2 phase is discussed. 相似文献
16.
《Analytical letters》2012,45(23-24):2293-2305
Abstract A highly sensitive voltammetric approach for trace measurements of mitomycin C is described. The method is based on controlled adsorptive accumulation of the drug at the hanging mercury drop electrode, followed by voltammetric measurement of the surface species. After five min preconcentration, a detection limit of 2 × 10?9 M mitomycin C is obtained. The adsorptive stripping response is evaluated with respect to electrolyte, pH, preconcentration time and potential, concentration dependence, possible interferences, and other variables. The relative standard deviation at 1 times; 10?7 M is 4%. Cyclic voltanmetry is used to characterize the redox and interfacial processes. 相似文献
17.
《Analytical letters》2012,45(16):3050-3059
Abstract Electrochemical investigation of the interaction of Ascorbic acid (AA) with bovine serum albumin (BSA) on a glassy carbon electrode is reported for the first time. In a 0.1 mol/l, pH 7.3 NaCl solution, AA had a well‐defined voltammetric oxidative peak at +0.2086 V (versus Ag/AgCl) on a GC electrode. After the addition of BSA into the AA solution, the oxidative peak current decreased significantly without a shift of the peak potential, and no new peak appeared. The experimental results showed that a new nonelectrochemical supramolecular complex was formed after the interaction of BSA with AA, which resulted in a decrease of the diffusion coefficient, and then a decrease of the oxidative peak current. The interaction conditions and the electrochemical detection conditions were carefully investigated. The stoichiometry of this supramolecular complex was calculated based on voltammetric data with a binding number of two and a binding constant of 1.38×107. 相似文献
18.
《Analytical letters》2012,45(9):1087-1102
Abstract The voltammetric behavior and measurement of nicardipine at the glassy carbon, carbon paste and hanging mercury drop electrodes are discussed. Cyclic voltammetry is used to elucidate the redox mechanism. Nicardipine is shown to adsorb on carbon electrodes, with the surface species retaining its electroactive characteristics. The adsorptive accumulation serves as a preconcentration step which improves the voltammetric measurement with respect to selectivity and sensitivity. Coupling this with a medium-exchange step eliminates interferences due to solution-phase electroactive species and permits direct measurement in urine. The inherent sensitivity of differential pulse voltammetry at the mercury electrode permits convenient measurement at the submicromolar level, with detection limit of 2 × 10?8M. Amperometric detection for a flow injection system is illustrated. 相似文献
19.
Khachatryan KS Smirnova SV Torocheshnikova II Shvedene NV Formanovsky AA Pletnev IV 《Analytical and bioanalytical chemistry》2005,381(2):464-470
The phenolic compounds phenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 1-naphthol, 2-naphthol, and 4-chlorophenol are extracted nearly quantitatively from aqueous solution into the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) in molecular form at pH<pKa. Picric acid is extracted efficiently in anionic form. Recovery of pyrocatechol and resorcinol is much lower. The effect of pH, phenol concentration, and volume ratio of aqueous and organic phases were studied. Ionic liquid BMImPF6 is shown to be suitable for extraction–voltammetric determination of phenols without back-extraction or addition of support electrolyte. The electrochemical window of BMImPF6 at various electrodes was determined, and voltammetric oxidation of phenols and reduction of nitrophenols in BMImPF6 was studied. 相似文献
20.
T. S. Rozhanchuk O. Yu. Tananaiko E. A. Mazurenko O. A. Egorov 《Journal of Analytical Chemistry》2012,67(2):156-162
The analytical prospects of a carbositall electrode modified with a film based on SiO2, hemoglobin (Hb), and gold nanoparticles (CSE SiO2-Hb-Au), prepared by deposition with an electrically generated catalyst, are reported. Hemoglobin on the surface of CSE SiO2-Hb-Au is shown to possess electrocatalytic activity toward dissolved oxygen, giving a rationale for the development of a
rapid voltammetric procedure of O2 quantification with a detection limit of 0.1 mg/L. The inhibition activity of a number of nitrogen-containing organic substances
to the catalytic current CSE SiO2-Hb-Au is studied. A voltammetric procedure is proposed for determination of the anti-flu drug rimantadine, 1-(1-adamantyl)ethylamine
hydrochloride, with a detection limit of 0.4 mg/L. The procedure is applicable to the quantification of rimantadine in blood
serum and saliva. 相似文献