The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
A method for analysing traces of nitrites is described. The method is based on the diazotization of a heteroaromatic primary amine--4-methyl-7-aminocoumarin (Coumarin 120 )--by nitrite ions in acidic medium. A large excess of Coumarin 120 is mandatory for a quantitative reaction. The corresponding in-situ-produced diazonium salt is stable at room temperature and can be selectively isolated in...
A new method for the determination of nalidixic acid in urine is proposed for concentrations between 25 and 1000 ng ml -1 by means of matrix isopotential synchronous fluorescence spectrometry. This new technique is useful for the determination of compounds in samples with unknown background fluorescence, such as nalidixic acid in urine, without the need for tedious preseparation.The...
In a 0.050 M HCl solution containing 0.12 M KCl, enoxacin yields a sensitive polarographic wave at -1.05 V, which can be used to determine trace amounts of the drug, the linear range being from 1.6 10 -8 to 1.6 10 -5 M with a detection limit of 6.25 10 -9 M. The electrochemical characteristics of the drug were studied by normal polarography, cyclic voltammetry...
The polynuclear complexation of divalent 3d transition metal cations with N,N,N ,N -tetrakis(2-pyridylmethyl)-1,2-ethanediamine (tpen) in aqueous solution was investigated. It was found that copper(II) forms a dinuclear complex with tpen in an aqueous solution containing chloride. The composition of the complex was determined as Cu 2 Cl 2 (tpen) 2+ . Furthermore, the...
The complexes of the rare earth metals with 2-phenyltrifluoroacetone in the presence of TX-100 are reported. The characteristic absorbances of neodymium, holmium and erbium complexes can be increased by factors of 8.5, 31 and 15 respectively, compared to those of the cholrides. The third-derivative spectra have been used to eliminate the interference of cerium, and the sensitivities are increased...
This paper describes an improvement in detection capability of microwave plasma torch atomic emission spectrometry by using a flow-injection on-line column preconcentration system. The analytical performances of Cd, Cu, Mn and Zn were studied. The analytes were preconcentrated with a thiol resin. The preconcentration period, the pH of the sample solution and the HCl concentration in the eluant were...
This work presents an overview of electrochemical techniques, namely potentiometry, amperometry, tensammetry, electrocapillary measurements and biosensors, recently applied for the determination of surfactants.
A sequential injection spectrophotometric method for stoichiometric studies, optimization and quantitative determination of ciprofloxacin and norfloxacin was developed. The work is based on the complexation reaction of ciprofloxacin and norfloxacin with iron(III) in sulfuric acid media and a spectrophotometric measurement of absorbances of the corresponding complexes at 447 and 430 nm respectively...
An accurate high performance liquid chromatography method for the separation and quantification of a solution mixture of nitrazepam, diazepam and medazepam and medazepam was developed. The modified simplex program has been utilized for the optimization of the chemical and chromatographic parameters using the chromatographic response function as the quality criterion and a photodiode array as a detector...
A novel photothermal phase-shift spectroscopy configuration based on the retro-reflected beam interference has been developed and its operational principle is described. The weak absorption measurement ability of this technique is experimentally proven with a water/ethanol solution of standard Pyronine G dye and the limit of detection is found to be 1.8 10 -6 absorbance. Potential...
Permeation of seven lanthanides (Ln) and thorium through a supported liquid membrane containing di-(n-octyl)phosphoric (DOPA) or di-(n-pentyl)phosphoric (DPPA) acid as a carrier has been studied as a function of the chemical composition of the system. The results have been compared with a previous study in which di-(2-ethylhexyl)phosphoric acid was used.Metal cations were transported from feed solutions...
Serum is rapidly digested with a mixture of nitric and perchloric acids at a temperature of 180 ± 10°C, and hydrochloric acid is used to reduce selenium(VI) to selenium(IV). Selenium is determined by hydride generation flame atomic absorption spectrometry. The results show that this method has the advantages of being sensitive, accurate, rapid and simple. After the serum is digested and diluted,...
A thickness shear mode bulk acoustic wave sensor coated with a thin liquid culture medium film was developed and applied to determine the concentration of Proteus mirabilis (P. mirabilis). Experiments demonstrated that there was a good linear relationship between the turning point time and the logarithm of the P. mirabilis concentration in the range 2.0 10 2 -2.0 10 6 cells ml ...
A simple and rapid spectrophotometric method for the determination of Isoproturon and Metoxuron is described based on alkaline hydrolysis of the compounds to their corresponding primary amines, followed by diazotization and coupling with ethylacetoacetate in alkaline medium. The chromogenic species obeys Beer's law up to 15 and 9 μg ml -1 for Isoproturon and Metoxuron respectively. ...
Critical statements have appeared recently in the literature concerning the need for classical dry ashing in trace element analysis of biological materials. In contrast, respected institutions (AOAC, Nordic Committee on Food Analysis, etc.) as well as numerous other laboratories have developed, verified, and/or successfully used classical dry ashing in practical analyses of a number of materials...
A method is proposed for the simultaneous determination of iron(III) and molybdenum(VI) by first-derivative spectrophotometry based on the absorption spectra of their complexes with morin in the presence of a cationic surfactant. The zero-crossing measurement technique is found suitable for the direct measurement of the first-derivative value at the specified wavelengths. Iron(III) (0.9-1.5 μg ml...
We have developed a simple, rapid, inexpensive method for the determination of benzo[a]pyrene (BP, a known carcinogen) in smoking-flavour agents (water-soluble liquid smoke; WSLS). After purification of the WSLS by a single passage through a Sep Pak C18 Plus cartridge, BP in the hexane eluate was determined by second derivative constant-wavelength synchronous spectrofluorimetry. Method precision...
A simple and sensitive spectrophotometric method is developed for the determination of titanium in aqueous medium. The metal ion forms a reddish brown coloured complex with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) in the pH range 1-7. The complex shows two absorption maxima, one at 430 nm and the other at 500 nm. The reagent shows appreciable absorbance of 430 nm and negligible...
The computer program sparc was used to calculate the pK a values of some important pharmaceutical substances. Thesparc models proved to be suitable for estimating the pK a values of beta-adrenergic blocking agents and benzodiazepine drugs. Ionization macroconstants, microconstants, zwitterionic equilibria, speciation curves as a function of the pH and the isoelectric points of a...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.