Talanta
A method for the extraction-spectrophotometric determination of palladium with 3,4,4a,5-tetrahydro-3,3,4a-trimethyl-7-(substituted)-pyrimido(1,6-a)benzimid azole-1-thiol (PBT) is described. PBT-Pd(II) complex is extracted from an acidic aqueous solution (0.01-0.5 M HClO 4 ) into a chloroform layer. The absorbance is measured at 438 nm and the molar absorptivity found to be 1.033 10 ...
Nitroso R salt and potassium ferricyanide, in hydrochloric acid, have been used as the reaction medium for simultaneous generation of arsine and plumbane, combined with inductively coupled plasma-atomic emission spectrometric detection. Both of the reagents enhance the lead signal and neither reagent inhibits the arsenic signal, provided that the potassium ferricyanide is mixed on-line with the analyte...
A potentiometric method for the titration of tetrabutylammonium iodide (TBAI) in chloroform using tetrabutylammonium periodate (TBAPI) as a strong and suitable oxidizing reagent is described. The potentiometric conditions were optimized and the equilibrium constants of the reactions occurring during the titration were determined. The method was used for the determination of iodide both in chloroform...
A thermodynamic study based on concepts of generalized species and equilibria, was used to understand the distribution of Fe(III) and Fe(II) species in the Fe(III)/Fe(II)/H 2 SO 4 /H 2 O system. The two-dimensional predominance zone diagrams (TDPZ) and Pourbaix type diagrams thus obtained permitted the selection of optimum experimental conditions, to differentiate the chemical...
Two simple and sensitive extractive spectrophotometric methods for the determination of some fluoroquinolone derivatives (norfloxacin, NRF; ciprofloxacin, CPF; ofloxacin, OFL; and enrofloxacin, ERF) with Supracene Violet 3B (SV 3B, method A) and tropaeolin 000 (TP 000, method B) are described. The methods are based on the formation of ion-association complexes of fluoroquinolones with these dyes,...
Application of the unified physicochemical approach to the description of the dissociation properties of Laurentide fulvic acid, extracted from peat, has shown that five predominant acidic moieties may account for the observed potentiometric titrations in aqueous medium. Information from non-aqueous titrations and titrations in presence of excess metal ions, e.g. Cu 2 + and Eu 3 ...
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 T M 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...