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A review is presented on thiocyanate methods for the estimation of molybdenum in a wide variety of samples. They include conventional thiocyanate methods in which molybdenum forms an orange red complex with the thiocyanate ions and improved thiocyanate methods where the sensitivity is increased through the formation of ternary ion association complex.
Monte Carlo simulations are employed to investigate the bias in linear regression parameters for cases in which both variables are subject to normally distributed errors. Both homoscedastic and heteroscedastic errors are treated. The results show that, in general, the arithmetic mean, geometric mean, and angle mean (tangent of the mean of the arctangents) of the slopes are biased and non-normally...
Cr(III) slowly forms a violet complex with EDTA at pH 3.5 ± 0.2 under normal conditions. The complex formation can be catalyzed by irradiating the reacting mixture with ultrasonic waves. Quantitative formation of the complex was possible with ultrasonic waves of 15 W/cm 2 intensity within 7.5 min of sonication. This method may be successfully applied to the determination of chromium in...
A fiber-optic probe for measuring chlorine in aqueous solution is evaluated. The probe uses a microporous gas-permeable membrane to trap a small volume of aqueous internal solution made ofN -(6-methoxyquinolyl)acetoethyl ester (MQAE) in front of a fiber-optic assembly. The working principle of this probe is based on a combination of fluorescence quenching and redox reaction of MQAE by chloride ion...
Polypyrrole (PPy)-coated platinum modified electrode was prepared electrochemically in chloroform in the presence of tetrabutylammonium perchlorate, tosylate, tetrafluoroborate, periodate, and hydrogen sulphate. Evidence in favour of the occurrence of a redox reaction at the film/solution interface was given by ferrocene oxidation. The electrocatalytic effect of the PPy-coated electrode was revealed...
Potentiometric stripping analysis (PSA) was used for determination of conditional stability constants (β ) of copper(II) complexes. Glycine was used as a model of a non-adsorbable ligand on the mercury electrode that forms well defined 1:1 and 1:2 copper(II)-glycine complexes, which are labile within the time scale of the analytical technique. The calculations were performed by the DeFord-Hume...
It was proved that the N 4 -oxide group included in chlordiazepoxide (CDZ) is involved in its phototoxicity. At a wavelength of 350 nm, CDZ photoisomerizes only into oxaziridine (OXA) which is not available as standard. In the course of cytotoxicity investigations, the optimal CDZ irradiation conditions were established as acetonitrile as solvent, 10°C as temperature of the irradiated solutions...
A sensitive method for the determination of lead in preserved egg by flame absorption spectrometry using ammonium pyrrolidine dithiocarbamate-polystyrene chemically modified platinum wire matrix is presented. The modified platinum wire matrix, after preconcentrating the lead, is placed in a flame burner for direct atomization and measurement. The concentration range is linear between 5 and 500 ng/ml...
Methods for determination of titratable acidity, other than traditional titration, i.e. methods without titration, are considered. A number of them use analytical acid-base reagents which quickly convert a mixture of strong and weak acids into a new system. This conversion makes it possible to obtain directly the analytical signal (pH, optical density, etc.) for titratable acidity calculation. ...
A trifluoroacetic anhydride-sodium iodide mixture (TFAA-I) reacts with nitroxide radicals with liberation of iodine. Since stoichiometric amounts of iodine are formed from nitroxides, the TFAA-I reagent can be applied to their analytical determination. Two procedures for the determination of nitroxides (titrimetric on μmol and spectrometric on nmol levels) are described.
Based on the principle of enzyme inactivation, a butyrylcholinesterase (EC 3.1.1.8.) biosensor, to determine some organophosphorus (ORP) pesticides (Fenitrothion, Diazinon, Parathion ethyl, Mevinphos and Heptenophos) in soil extracts, is presented. The enzyme was immobilized on pre-activated Pall Biodyne TM transfer membranes, which were physically attached to the sensitive ends of glass...
A method is proposed for the extraction and mutual separation of quadrivalent titanium, zirconium and hafnium from hydrochloric acid using triphenylphosphine oxide dissolved in toluene as an extractant. The optimum conditions for the extraction and separation have been evaluated from critical study of acid concentration, extractant concentration, period of equilibration and effect of diluent. The...
A porous cellulose tape impregnated with a processing solution that includes 4-p-nitrobenzylpyridine,N -benzylaniline and methanol is a highly sensitive means of detecting phosgene and maintains stable sensitivity for at least three months in air in a desiccator. When the sample including phosgene was passed through the tape, the color of tape changed to red. The degree of color change was proportional...
Four different calibration methods were used for quantitative analysis of quartz and calcite in atmospheric aerosols by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS): (A) conventional calibration with one measurement on each standard (single calibration); (B) calibration with an internal standard; (C) calibration with parallel (n = 4) measurements on each standard (multiple...
A polystyrene divinyl benzene based resin containing bicine groups has been prepared and its analytical properties investigated. The pH dependence of sorption of metal on the resin has been determined for Cu(II), Fe(II), Ni(II), Co(II), Zn(II), Hg(II) and Pb(II). The important characteristics of the resin are fast equilibrium, high selectivity and small volume change between its hydrogen and metal...
Solver, an analysis tool incorporated into Microsoft Excel V 5.0 for Windows, has been evaluated for solving non-linear equations. Test and experimental data sets have been processed, and the results suggest that solver can be successfully used for modelling data obtained in many analytical situations (e.g. chromatography and FIA peaks, fluorescence decays and ISE response characteristics). The...
The complexation of urea (ur) with manganese(II), nickel(II) and zinc(II) ions has been studied by titration calorimetry in N,N-dimethylformamide (DMF) containing 0.4M (C 2 H 5 ) 4 NBF 4 as a constant ionic medium at 25°C. The calorimetric data were well explained in terms of the formation of [Mn(ur)] 2+ , [Mn(ur) 2 ] 2+ and [Mn(ur)...
A new method has been developed for the spectrophotometric determination of l-dopa in pharmaceutical formulations. The method is based on the reaction between the open-chain quinone ofl -dopa, obtained in NaOH, and the benzoqinoneimine form of p-aminophenol, in the presence of KIO 4 . The reaction product is determined at 574 nm by using both alternately procedures, one based on the stopped-flow...
Fast heating programmes for determining aluminium and chromium in vegetables using electrothermal atomic absorption spectrometry with slurry sampling are developed using wall atomization. The build-up of carbonaceous residues inside the atomizer is avoided by adding 4% hydrogen peroxide and 1% nitric acid to the slurries instead of using an air-ashing stage. In accordance with fast-programme methodology,...
A new analytical method was developed for the determination of ascorbic acid. The method is based on the reaction of ascorbic acid with 4-chloro-7-nitrobenzofurazane (NBD-Cl) in the presence of 0.2M sodium hydroxide, where a bluish green colour (λ max 582 nm) is developed after dilution with 50% (v/v) aqueous acetone solution. Beer's law was obeyed in a concentration range of 5-20...
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