New Electrochemical Method For Determination Research Articles

A new modification method of a Cetyl Trimethyl Ammonium Bromide/Nano-ZnO and Multi-walled Carbon Nanotubes Electrode for Determination of Anti Doping in Urine

The preparation and application of Cetyl Trimethyl Ammonium Bromide/Nano-ZnO and Multi-walled Carbon Nanotubes (CTAB/ZnO-MWNTs) Modified Electrodes was studied, establishing a new electrochemical method for determination of carteolol hydrochloride in urine. After its pre-enrichment by adsorption and extraction on modified electrodes, electrochemical behaviors of carteolol hydrochloride on the modified electrodes were studied by CV and DPV. The response is linear at the range of 1×10-3 ∼ 2×10-1 g/L, with a detection limit of 2×10-4 g/L. Under appropriate conditions, the content of carteolol hydrochloride in urine can be determined directly by the method, which had strong anti-interference ability and the recovery is 96.5% - 110.5%. In addition, extraction and adsorption behaviors of the modified electrodes for carteolol hydrochloride were studied by chronocoulumetry, and the results showed that extraction during the enrichment process played a major role at low concentrations, and contribution of surface adsorption became greater with the increase of concentrations.

Development and Validation of Chronopotentiometric Method for Imidacloprid Determination in Pesticide Formulations and River Water Samples.

A new electrochemical method for determination of imidacloprid using chronopotentiometry on thin film mercury and glassy carbon electrode was presented. The most important experimental parameters of chronopotentiometry were examined and optimized with respect to imidacloprid analytical signal. Imidacloprid provided well-defined reduction peak in Britton-Robinson buffer on thin film mercury electrode at −1.0 V (versus Ag/AgCl (KCl, 3.5 mol/L)) and on glassy carbon electrode at −1.2 V (versus Ag/AgCl (KCl, 3.5 mol/L)). The reduction time was linearly proportional to concentrations from 0.8 to 30.0 mg/L on thin film mercury electrode and from 7.0 to 70.0 mg/L on glassy carbon electrode. The detection limits were 0.17 mg/L and 0.93 mg/L for thin film mercury and glassy carbon electrode, respectively. The estimation of method precision as a function of repeatability and reproducibility showed relative standard deviations values lower than 3.73%. Recovery values from 97.3 to 98.1% confirmed the accuracy of the proposed method, while the constancy of the transition time with deliberated small changes in the experimental parameters indicated a very good robustness. A minor influence of possible interfering compounds proved good selectivity of the method. Developed method was applied for imidacloprid determination in commercial pesticide formulations and river water samples.

New electrochemical method for the determination of β-carboline alkaloids, harmalol and harmine, in human urine samples and in Banisteriopsis caapi

In this paper a new electrochemical method for determination of the β-carboline alkaloids, harmalol and harmine, using differential pulse voltammetry is presented. Experimental parameters such as pH, scan rate, pulse amplitude and pulse time were optimized to characterize their electrochemical behavior and to find best analytical conditions. Thus, in the presence of ascorbic acid, uric acid, dopamine, the developed method exhibits excellent performance for the determination of harmalol and harmine for a linear concentration range between 1–50μM and 1–75μM with a detection limit of 0.6μM and 0.2μM, respectively. The proposed method was successfully applied for the determination of these alkaloids in a sample of an Ayahuasca liana (Banisteriopsis caapi) and in model human urine samples with good recoveries.

A new electrochemical method for trace water determination in methanol

A new electrochemical method for the determination of trace water in methanol has been developed. This method is based on the effect, that a minor change in the water content affects the value of conductivity measured for dissolved in the solutions electrolyte. The conductivity measurements were performed for four inorganic salts, i.e. NaCl, KCl, RbCl, and CsCl in solutions with different amounts of water traces in methanol and the calibration curves for three of them were determined. With the exception of cesium chloride the high values of correlation coefficients for the regression lines as well as low limits of detection were achieved in all cases which indicates that this method is a useful tool for the determination of the trace amounts of water in methanol.

Measurement of lipase activity by a differential pH technique.

This is a new electrochemical method for determination of lipase activity in biological fluids, including serum, plasma, and duodenal juice. Advantages of turbidimetric methods--short reaction time, and small sample and reagent volumes--are combined with those of titrimetric methods: measurement of absolute activity (i.e., no standardization required), saturated substrate conditions, and direct measurement of reaction products. The proposed method is easy, inexpensive, and takes only 3 min. Precision is good: CV = 3.74% within day and 7.3% between days at the clinical-decision concentration, CV = 1.86% within day and 4.65% between days for above-normal lipase activities. The standard curve is linear up to 4500 U/L. Results (y) correlate well with those by turbidimetry (x): y = 0.9287x - 65.3 (r = 0.9719). Reference values are between 0 and 130 U/L.

ChemInform Abstract: POLAROGRAPHIC STUDIES ON BIPYRIDINE COMPLEXES PART 2, CORRELATION BETWEEN CHARGE‐TRANSFER FREQUENCIES AND OXIDATION POTENTIALS OF TRIS(2,2′‐BIPYRIDINE) COMPLEXES OF IRON, RUTHENIUM, OSMIUM, COBALT AND CHROMIUM

Summary A linear relation is predicted to exist between frequencies of charge-transfer bands of a series of transition metal complexes with different ligands and their oxidation potentials corrected for the electron affinities of acceptor ligands. The relation is proved to hold for the tris(2,2′-bipyridine), tris(4,4′-dimethyl-2,2′-bipyridine) and tris(5,5′-dimethyl-2,2′-bipyridine) complexes of iron(II), ruthenium(II), osmium(II), cobalt(I) and chromium(II). On the basis of the fact that the electronic configuration of any one of these complexes and its one-electron oxidation product differs by one in the number of electrons in the t 2g -orbitals, an empirical rule is obtained: When a metal t 2g -electron is removed by electrochemical oxidation of a tris(2,2′-bipyridine) complex of a transition metal, the oxidation half-wave potential is shifted to a more negative potential on methyls substitution of ligand bipyridines in the order, bipyridine 9 , the present findings suggest a new electrochemical method for determination of the electronic configuration of tris(2,2′-bipyridine) complexes of transition metals.

Polarographic studies on bipyridine complexes II. Correlation between charge-transfer frequencies and oxidation potentials of tris(2,2′-bipyridine) complexes of iron, ruthenium, osmium, cobalt and chromium

A linear relation is predicted to exist between frequencies of charge-transfer bands of a series of transition metal complexes with different ligands and their oxidation potentials corrected for the electron affinities of acceptor ligands. The relation is proved to hold for the tris(2,2′-bipyridine), tris(4,4′-dimethyl-2,2′-bipyridine) and tris(5,5′-dimethyl-2,2′-bipyridine) complexes of iron(II), ruthenium(II), osmium(II), cobalt(I) and chromium(II). On the basis of the fact that the electronic configuration of any one of these complexes and its one-electron oxidation product differs by one in the number of electrons in the t2g-orbitals, an empirical rule is obtained: When a metal t2g-electron is removed by electrochemical oxidation of a tris(2,2′-bipyridine) complex of a transition metal, the oxidation half-wave potential is shifted to a more negative potential on methyls substitution of ligand bipyridines in the order, bipyridine <5,5′-dimethylbipyridine <4,4′-dimethylbipyridine. Combined with the conclusion of Part I9, the present findings suggest a new electrochemical method for determination of the electronic configuration of tris(2,2′-bipyridine) complexes of transition metals.