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A chemically modified electrode (CME) constructed by adsorption of aquocobalamin (VB12a) onto a glassy carbon electrode surface was demonstrated to catalyze the electro-oxidation of cysteine, a sulfhydryl-containing compound. The sulfhydryl oxidation occurred at 0.54-0.88 V vs. Ag/AgCl depending on pH value (3.0-10.0). The electrocatalytic behavior of cysteine is elucidated with respect to solution...
A method for the simultaneous determination of sulphide and sulphite is described, which involves continuous H 2 S and SO 2 generation, preconcentration in a liquid nitrogen trap and measurement of the molecular absorption spectra of volatiles in the gas phase in 190-220 nm range. Under the recommended conditions (sample flow: 50 ml/min and concentrated sulphuric acid flow: 12 ml/min;...
Trimethylsilyl derivatives of 10 different hydroxy- and methoxyhydroxyflavonoid compounds were studied by the GC-FTIR technique. Optimal deviation parameters were determined for the flavonoids studied. The correlation found between retention and gas-phase IR data can successfully be used in structural identification of compounds having very similar chromatographic behaviour. The shift of the carbonyl...
A new sample chamber was developed that can be used in the measurement of the effects of moisture on the room-temperature solid-matrix phosphorescence of phosphors adsorbed onto filter paper. The sample chamber consists of a sealed quartz cell that contains a special teflon sample holder. Sulfuric acid solutions in the quartz cell determine the percentage relative humidity in the cell and also determine...
A method for the determination of aniline was developed, based on the diazotization and coupling of the aromatic amine to form an azo compound capable of being determined by adsorptive stripping voltammetry. A fast derivatization procedure was developed using 1-naftol as the coupling agent. A detection limit of 0.8 μg/l was obtained for aniline, using an accumulation time of 2 min. The method was...
A very sensitive electrochemical procedure for trace determination of antimony is described. The complex of antimony with p-dimethyl-aminophenyl-fluorone (p-DMPF) is adsorbed on a hanging mercury drop electrode (HMDE), and the reduction current of the accumulated complex is measured by voltammetry. In linear sweep voltammetry, the reduction potential of the complex is more positive than that of...
The contact charge transfer (CCT) absorption spectra of dimethylsulphoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), ethanol, methanol, water, benzene (Bz), N,N -diethylaniline (DEA), N,N -dimethyl-p-toluidine (DMT) and N,N -diethyl-p-toluidine with molecular oxygen have been investigated. These solvents form strong ultraviolet/visible CCT absorption spectra with intensities...
The separation and determination of platinum metal and co-existing metal complexes by reversed-phase high performance liquid chromatography (HPLC) with 2-(6-methyl-2-benzothiazolylazo)-5-diethylamino phenol (MBTAE) as a precolumn derivatizing reagent is presented. The separation mechanism of these complexes was investigated by combining spectrophotometry with HPLC while salicylic acid was contained...
A simple, rapid and economic method has been developed for the reduction of potassium permanganate in alkaline carbonate uranium leach liquors to a colourless solution. The pink colour of permanganate, if not reduced, seriously impedes the determination of carbonate, bicarbonate and phosphate by titrimetry and spectrophotometry. Out of 17 reductants investigated, commercial sugar has been found...
We describe a fast, new method for determination of the joint concentration of the six polycyclic aromatic hydrocarbons (PAHs), designated by current legislation as indicators of the quality of drinking waters and surface waters intended for the abstraction of drinking waters. The limit of detection of the new method was 6 ng l -1 , its limit of quantification 20 ng l -1 ...
The determination of several N-substituted phenothiazine derivatives was carried out by the reaction of the drug with manganese dioxide entrapped in a polymeric material in a packed-bed reactor; the oxidized drug was monitored at λ max . The calibration graph is linear over the range 5-50 μg/ml of phenothiazine derivatives with a relative standard deviation of 0.5-1% (at 10 μg/ml)...
Arsenic has been determined by β-correction spectrophotometry with ethyl violet (EV) in the presence of sodium nitrite which is an oxidant and effective for removing absorption spectra and increasing analytical sensitivity. Extraction with benzene can separate most other metals ions and concentrate arsenic in wastewater. The β-correction method can eliminate completely the effect of excess EV in...
Chemiluminescent reagents for the determination of residual ozone were compared. Each method was automated using gas diffusion flow injection analysis. The luminol method gave a four order of magnitude working range with an LOD of 0.008 mg O 3 /l. The luminol method has better analytical characteristics than the standard colorimetric Indigo Blue methods
A technique based on pattern recognition of data obtained by supersonic jet spectrometry is employed for the prediction of chemical structure. The degree of similarity is evaluated quantitatively by calculating a cross correlation factor between sample and reference molecules. A probability density function is determined by fitting the data to a specified equation. The functional group and its position...
2-Mercaptobenzothiazole loaded on previously treated clay was prepared, characterized and used for sorption and preconcentration of Hg(II), Pb(II), Zn(II), Cd(II), Cu(II) and Mn(II) from an aqueous solution. The support used was a natural clay previously treated with sulphuric acid solution. Adsorption isotherms of metal ions from aqueous solutions as function of pH were studied at 298 K. Conditions...
The equilibrium constants of α,β,γ,σ-tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) complexes of cadmium(II), lead(II), magnesium(II), and zinc(II) were spectrophotometrically determined using the absorption spectra at the Soret band and the fluorescence spectra. The values of the following constants at 25°C and ionic strength 0.1 M were evaluated: K Pb-P =10 -8...
Following the treatment of the sample with zinc hydroxide, nitrite reacts with potassium iodide in the presence of acetone and sulphuric acid. The released iodine and the propanone derivative resulting from the acetone are extracted in n-hexane. The extract is subjected to gas chromatographic separation and detection using an electron capture detector. The calibration curve was found to be linear...
The study describes a new wet chemical technique, termed ANM, for the isolation of secondary phases in magnesite processed at a temperature of 1650 °C. The major MgO (periclase) phase in processed magnesite was preferentially extracted as ammonium nitrate magnesium double salt by ammonium nitrate in ethanol medium. The residues containing enriched secondary phases were identified by XRD.
The literature on metal ion speciation in solid matrices is reviewed, taking into account its applications in the analysis of soil, sediment, biological materials, foodstuff and other solid samples. The pretreatment methods of various solid materials required for carrying out speciation studies have been highlighted. The basis of the methods of separation of different species from matrices, such...
The stability constants of the complexes of glycinate ion with copper(II), nickel(II) and hydrogen(I) and of nitrilotriacetate ion with calcium(II) and hydrogen(I) and the ionic product of water (K w ) were determined potentiometrically. The measurements were carried out at 25.0 °C in four different ionic strengths up to I (=I c ) = 2.50 and two different ionic media (KNO 3 ...
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