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Carbaryl and its hydrolysis product, 1-naphthol, are determined simultaneously, and in a mixture of other pesticides, by reversed-phase high-performance liquid chromatography (HPLC). Fluorometric detection affords a higher degree of selectivity than absorbance detection, while providing detection limits of 1.0 ng ml -1 and 1.4 mg ml -1 for 1-naphthol and carbaryl, respectively...
After reaction with nitric acid, brucine can be transformed into cacotheline, and then measured indirectly by adsorptive stripping voltammetry. This method is based on the adsorptive accumulation of cacotheline at a hanging mercury drop electrode, followed by cathodic linear sweep voltammetry. The cathodic peak potential is about -0.35 V (vs. saturated Ag/AgCl). The detection limit of 2.0 10...
The application of evolving projection analysis (EPA) to second-order bilinear data sets consisting of more than two components is described. EPA is a method for rank analysis of ordered data matrices where the components appear sequentially as a function of time or some other ordinal variable. It was found that extension of the method to mixtures of more than two components was best accomplished...
A matrix modifier composed of nickel and zirconium, and a graphite tube treated with zirconium solution were proposed for the determination of boron in cobalt-based alloys by graphite furnace-atomic absorption spectrometry. The effects of this matrix modifier and the treated graphite tube were studied, and the combination of 60 μg of nickel and 20 μg of zirconium as matrix modifier, and a graphite...
A method is described for the determination by solid phase spectrophotometry (SPS) of trace amounts of vanadium in natural water and crude petroleum samples. The procedure is based on fixation on a dextran-type anion exchanger of the complex V(IV)-Eriochrome Cyanine R. The absorbance of the gel, at 563 and 750 nm, packed in a 1 mm cell, is measured directly. Vanadium can be determined in the 0.6-25...
The ability of chelation chromatography in combination with differential pulse anodic stripping voltammetry (DPASV) to provide a simple, fast and reliable way of dealing with interionic interferences, competitive complexations, re-adsorption of released metal ions and sorption of spiking metal ions by organic/inorganic materials in the complex matrixes of real natural samples has been critically examined...
Potentiometric multiple addition of a sample containing a pure weak acid to a solution of supporting electrolyte has been previously shown [C. Macca and A. Merkoci, Talanta, 41 (1994) 2033] to be formally suitable for the determination of the dissociation constant and concentration of the sample acid. Linear equations have been developed for the treatment of experimental data to yield, simultaneously...
A first-derivative spectrophotometric method is described for the simultaneous determination of Ru(III) and Rh(III) using octadecyl dithiocarbamate. The complexes are insoluble in water, but easily extractable into chloroform. Quantitative determination of Ru(III) and Rh(III) is possible in the ranges 0.5-6.0 μg ml -1 and 1.0-10.0 μg ml -1 respectively, with a standard...
A new technique for the determination of low molecular weight organic acids in Bayer process liquors is reported. The acids are partitioned from acidified liquor into butanol, followed by butylation using microwave heating. This method is both rapid (sample preparation time < 15 min) and capable of detecting acids larger than previously reported in the low molecular weight fraction (up to RMM...
A modified computer program SCTPT for the computation of formation constants of extraction complexes with two-phase pH titration data by using the Marquardt-Fletcher algorithm is described. It can be used to deal with extraction systems which consist of a metal, an acidic extractant and a neutral synergistic reagent with no need of new subroutine. It has been applied successfully to the Pb-PMBP(1-phenyl-3-methyl-4-benzoyl-pyrazolone-5)-TBP...
A reasonably sensitive and highly selective spectrophotometric method for the determination of mercury(II) is proposed. The method is based on the extraction of the ion-associate formed by a mercury(II) thiacrown ether cationic complex with Bromocresol Green as the anionic counter-ion using chloroform as the extracting solvent. The effect of thiacrown ethers of different cavity sizes, namely 1,4,7,10,13-pentathiacyclopentadecane...
A sensitive, direct spectrofluorimetric method for the trace determination of terbium with use of trimesic acid (TMA) has been developed. The reaction conditions for the fluorescence system of terbium with TMA were studied. The terbium ion can form a stable binary chelate with TMA, having a ratio of 1:1 in the pH range 3.5-6.5. The maximum excitation and emission wavelengths are 260 nm and 545...
Three simple and sensitive spectrophotometric methods for the determination of tamoxifen citrate have been developed. They are based on the formation of an ion-association complex between the drug and a dye, Erioglaucine A, which is extractable into chloroform and has an absorption maximum at 625 nm (method A), oxidation with excess potassium permanganate and the determination of unconsumed permanganate...
Room-temperature phosphorescence characteristics of serotonin (5-hydroxytryptamine), typtamine, and gramine ([3-(dimethylaminomethyl)indole]) were studied on low-background paper substrates. Several experimental parameters were optimized for maximum signal intensity. Sodium iodide, thallium(I) nitrate, silver(I) nitrate, and lead(II) nitrate were tested as phosphorescence enhancers. The effect...
A method for the preconcentration of trace amounts of tungsten as its thiocyanate complex, using a column filled with Amberlite XAD-1180 resin, is proposed. After elution with a small volume of acetone, the analyte was determined spectrophotometrically with potassium thiocyanate and stannous chloride. The influence of several ions, as interferents, is discussed. The proposed method was applied to...
Chromatographic systems for the separation of amino acid mixtures on RP-18 as a stationary phase have been elaborated. The best results were obtained using methanol-water (1:1, v/v; 1:3, v/v; 1:5, v/v) as a mobile phase.The following amino acids have been examined: asparagine, arginine monohydrochloride, cystine, cysteine chloride, glycine, histidine monohydrochloride, hydroxyproline, isoleucine,...
Flow-injection analysis for the determination of hydrazine derivatives based on their nucleophilic substitution reaction with 4-chloro-5,7-dinitrobenzofurazan in aqueous medium, and spectrophotometric detection has been described. The calibration graphs were linear in the range from 0.15 to 4.0 μg ml -1 of hydrazine derivatives, with sampling rates of up to 28-32 samples h - ...
A method for the determination of salbutamol in both tablets and syrups is described. It utilizes the reduction of the Folin-Ciocalteau reagent by the phenolic group, monitoring the absorbance of the resulting complex at 760 nm. Results obtained are linear over the range 0-6 μg ml -1 salbutamol. Coloring material was removed by anionexchange chromatography prior to analysis and there...
A new combination of a flow/sequential injection method for the analysis of ammonia has been developed. Gaseous ammonia is selectively absorbed in a phosphoric acid coated glass tube and determined with Berthelot reagents by flow injection. The combination of the gas diffusion denuder sampler with flow injection makes this method very sensitive and selective. The limit of detection of 0.15 μg NH...
A new method is proposed for the solvent extraction separation of cobalt(II) with hexaacetatocalix(6)arene in toluene. Cobalt(II) was extracted at pH 7.4 with 10 10 -4 M hexaacetocalix(6)arene, stripped with 2 M nitric acid, and determined spectrophotometrically at 500 nm as its complex with nitroso-R-salt. Cobalt was separated from any associated elements. The method was extended...
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