title stringlengths 0 1.13k | abstract stringlengths 1 15.7k | PMID int64 22 36.5M |
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Simultaneous determination of the acid and basic ionization constants of imidazole. | The acid and base ionization constants of imidazole (LH) have been determined simultaneously by potentiometry. Concentration constants were obtained at 10.0, 15.0, 25.0 and 40.0 degrees with I = 0.1M (KNO(3)), the values (and standard deviations) at 25.0 degrees being pK(a1)(LH(2)(+)) = 7.002 +/- 0.006 and pK(a2)(LH(2)... | 18,964,228 |
Relationship between muscle volume and muscle torque of the hamstrings after anterior cruciate ligament reconstruction. | The muscle torque per unit volume of the hamstrings on the injured and uninjured sides in patients with ACL reconstruction were compared with participants with no history of knee injury to examine whether a similar mechanism leading to quadriceps weakness exists in the hamstrings of these patients. The study population... | 18,964,233 |
[Not Available]. | The three natural xanthines, caffeine, theobromine and theophylline, have been determined by HPLC on columns of silica gel or a C(18)-bonded phase. For the determination in beverages, HPLC on silica gel was used. The method was applied to coffee, tea, maté, in extracts or in the drinks themselves. For the extracts a co... | 18,964,243 |
Analytical chemistry in the Soviet Union. | The history of the development of analytical chemistry in the Soviet Union is briefly outlined. Organizations co-ordinating research in this field, and the leading scientific centres, are indicated. Achievements in various analytical techniques are reviewed. Analytical services in some branches of the economy, and the ... | 18,964,256 |
Steric and hydrophobic effects of substituents in extraction of metal complexes with O,O-dialkyldithiophosphoric acids. | The two-phase stability constants (equilibrium constants) of metal complexes MA(n) [M(n)(+) = Ni(II), Zn(II), Cd(II), Pb(II), Tl(I), In(III)] with a series of O,O-dialkyldithiophosphoric acids in the system water-organic solvent) have been determined. By use of correlation analysis the role of the steric and hydrophobi... | 18,964,282 |
Extraction and preconcentration of selenium from aqueous solutions and its determination in water and hair samples by atomic-absorption spectrophotometry. | Several organic solvents, including benzene, xylene, toluene, nitrobenzene, chloroform, carbon tetrachloride, chlorobenzene and high molecular-weight pyridines such as 4-(5-nonyl)pyridine, 2-hexyl-pyridine and benzylpyridine have been investigated as components of systems for the extraction and preconcentration of sele... | 18,964,309 |
[Not Available]. | This paper describes the theoretical basis of a new program for refinement of complex stability constants together with the other parameters of various protometric titrations. The method is based on minimization of the sum of the weighted squares of the residuals of the experimental variables reagent volume and E or pH... | 18,964,321 |
Behaviour of a chalcocite copper ion-selective electrode in solutions of iron(III) ions. | The effect of iron(III) ions on the potential of the chalcocite electrode was investigated. Linear graphs were obtained for pFe(III) = 2-4, and were suitable for analytical purposes. The effect of ligands complexing iron(III) was studied, and the potential shown to be due to the concentration of free iron(III) ions onl... | 18,964,324 |
Constant Calcein Blue: An indicator for spectrofluorometric calcium determination. | A new fluorescent indicator for metal ions, called Constant Calcein Blue, has been synthesized by condensing 7-hydroxy-2,3-dimethylchromone, iminodiacetic acid and formaldehyde. The indicator exhibits extraordinary resistance to alkaline hydrolysis and is recommended for spectrofluorometric determinations of metal ions... | 18,964,328 |
A sub-microlitre two-photon ionizatio detector for high-performance liquid chromatography. | A simple sub-microlitre two-photon ionization detector for high-performance liquid chromatography has been constructed; it basically consists of a pulsed laser, a falling-jet cell, and a boxcar detection system. The performance of the cell has been evaluated; the cell is windowless and its volume is about 14 nl. A dye ... | 18,964,337 |
Phthalhydrazidylazoacetylacetone as a chemiluminescent acid-base indicator. | Phthalhydrazidylazoacetylacetone, an azo derivative of luminol, has been shown to be superior to luminol as a chemiluminescent indicator for acid-base titrations. | 18,964,346 |
Polargraphic adsorptive waves of alkaline-earth metal complexes with thymolphthalexone. | Sensitive derivative polarographic adsorption waves have been observed for alkaline-earth metal-TP complexes in 0.15M potassium hydroxide containing 3 x 10(-5)M thymolphthalexone (TP). The limit of detection for calcium, strontium and barium was 7.5 x 10(-7)M and for magnesium 4.0 x 10(-6)M. The proposed method has bee... | 18,964,358 |
Anodic-stripping voltammetric determination of arsenic at a copper-coated glassy-carbon electrode. | The anodic-stripping voltammetric behaviour of arsenic(III) at a glassy-carbon electrode copper-coated in situ has been investigated. The effects of copper concentration, acidity, deposition potential and sweep rate on the stripping peak have been examined and criteria are given for the choice of experimental condition... | 18,964,362 |
Signal processing with a summing operational amplifier in multicomponent potentiometric titrations. | It has been proved that application of two indicator electrodes connected to the ordinary titration apparatus through an auxiliary electronic device (a summing operational amplifier) significantly extends the scope of multicomponent potentiometric titrations in which the analytes are determined simultaneously from a si... | 18,964,366 |
[Not Available]. | The isotherms for adsorption of some organic molecules on asbestos fibres have been determined by gas chromatography. The results show that the adsorption mechanism lies somewhere between physisorption and chemisorption. The degree of adsorption at a given temperature, for the compounds studied, is toluene > tetrahy... | 18,964,367 |
Spectrophotometric determination of iron by extraction of the iron(II)-5,5-dimethyl-1,2, 3-cyclohexanetrione-1,2-dioxime-3-thiosemicarbazone complex. | The iron (II)-5,5-dimethyl-1,2,3-cyclohexanetrione-1,2-dioxime-3-thiosemicarbazone complex can be extracted from a medium of high acidity into amyl alcohol. Measurement of the absorbance at 550 nm gives a determination limit for iron of 0.015 mu/ml. The method has been applied to the determination of iron in water, win... | 18,964,380 |
Hydrodynamic voltammetry at tubular electrodes-III Determination of traces of bismuth by differential-pulse anodic-stripping voltammetry at a glassy-carbon tubular electrode with in situ mercury plating. | An equation for the current in differential-pulse anodic-stripping voltammetry at tubular electrodes is derived. Application of a glassy-carbon tubular electrode to determination of traces of bismuth in environmental water samples by differential-pulse anodic-stripping voltammetry is described. In hydrochloric acid med... | 18,964,381 |
Determination of hydrogen peroxide with N,N-diethylaniline and 4-aminoantipyrine by use of an anion-exchange resin modified with manganese-tetrakis(sulphophenyl)porphine, as a substitute for peroxidase. | Amberlite IRA 900 anion-exchange resin modified with manganese-tetrakis(sulphophenyl)-porphine has been used as a catalyst instead of peroxidase for the determination of hydrogen peroxide by the reaction 2H(2)O(2) + N,N-diethylaniline + 4-aminoantipyrine (catalyst)--> quinonoid dye (lambda(max) 550 nm) + 4H(2)O. The... | 18,964,384 |
Determination of alkaline-earth metals in foetus bones by inductively-coupled plasma atomic-emission spectrometry. | Alkaline-earth metals in human bone samples have been determined simultaneously by inductively-coupled plasma atomic-emission spectrometry (ICP-AES). Results obtained by atomic-absorption spectrometry for Mg, Sr and Ba, and complexometry for Ca, have been compared with those by ICP-AES for a laboratory-control bone sam... | 18,964,414 |
A simple and rapid fluorimetric method for the microdetermination of isonicotinic acid hydrazide. | A simple, rapid and sensitive fluorimetric method has been developed for the microdetermination of isonicotinic acid hydrazide, based on its formation of a hydrazone with 2-hydroxy-1-naphthaldehyde in acidic medium, in the presence of excess of scandium ions, and the consequent formation of a strongly fluorescent compl... | 18,964,419 |
Hydroxide complexes of lanthanides-VIII Lanthanum(III) in perchlorate medium. | From the precipitation borderline in the pLa'-pC(H) diagram the stability constants for (mononuclear) lanthanum-hydroxide species have been established. The presence of polynuclear species could not be demonstrated and seems unlikely. The values found were log *beta(1) = -8.6, log *beta(2) = -17.9, log *nu(3) = -27.3 a... | 18,964,420 |
Some analytical aspects of the measurement of heavy-atom kinetic isotope effects. | Measurements of the kinetic isotope effects of heavy atoms are discussed from an analytical point of view. The discussion includes the choice of isotope, the procedure for measurement, and methods for increasing the kinetic isotope effect. The procedures most commonly used and newly developed techniques are presented a... | 18,964,423 |
Determination of viscosity with an open-closed flow-injection system. | A flow-injection configuration for the determination of the viscosity of water-miscible samples is proposed. The method is based on the use of an open-closed flow-injection system involving a trapped sample (carrier) and injection of a dye plug. The behaviour of the plug is monitored photometrically by a detector inclu... | 18,964,432 |
Extraction of aromatic organic compounds by polyurethane foam. | The mechanism of extraction of organic compounds by open-cell polyurethane foam has been investigated through a detailed study with simple aromatic compounds. Comparison with identical extractions into diethyl ether suggests that the basic extraction mechanism is an ether-like solvent extraction process. The addition o... | 18,964,439 |
A rapid spectrophotometric method for determination of piperazine. | A spectrophotometric method has been developed for the determination of piperazine and its salts (citrate, phosphate, and tartrate) without prior separation, based on the interaction of piperazine or any of its salts with phenothiazine and N-bromosuccinimide in aqueous methanol. The products exhibit absorption maxima a... | 18,964,442 |
Determination of arsenic in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separation by xanthate extraction. | A method for determining approximately 0.2 mug/g or more of arsenic in ores, concentrates and related materials is described. After sample decomposition arsenic(V) is reduced to arsenic(III) with titanium(III) and separated from iron, lead, zinc, copper, uranium, tin, antimony, bismuth and other elements by cyclohexane... | 18,964,463 |
Simultaneous determination of low concentrations of ammonium and potassium ions by capillary type isotachophoresis. | Low concentrations of ammonium and potassium ions (<2.0 mg/l.) were determined simultaneously by capillary type isotachophoresis based on the interaction between potassium and 18-crown-6 in the aqueous leading electrolyte. The PU value of potassium ion increased with increasing concentration of 18-crown-6 up to 3mM,... | 18,964,464 |
A fiber-optic sensor for CO(2) measurement. | A fiber-optic sensor has been prepared which responds to carbon dioxide at physiologically significant concentrations. It is based on pH modulation by dissolved carbon dioxide in a sensing layer of fluorescent dye. By use of a previously developed methodology by which the sensing chemistry is bonded directly to the gla... | 18,964,477 |
Solid-state instrumentation for use with optical-fibre chemical-sensors. | A solid-state instrument has been developed for use with optical-fibre pH-sensors, which incorporates light-emitting diode sources and a photodiode detector. The instrument has an internal reference. The optical and electronic principles are described. The responses of the sensor and instrument are reported and compare... | 18,964,485 |
Determination of uranium at trace levels by radiochemical neutron-activation analysis employing radioisotopic yield evaluation. | Nanogram and picogram quantities of uranium were determined in biological materials by radiochemical neutron-activation analysis. Two different approaches using either (239)U or (239)Np were employed for cross-checking, and the question of negative errors due to incomplete acid dissolution of any possible inorganic (si... | 18,964,488 |
Modified reverse pulse polarographic behaviour of magnesium ion in aqueous solution. | Modified reverse pulse polarography (MRPP) is proposed for measuring the quantity of a reduction product formed at the initial potential in reverse pulse polarography. A double potential-step method is employed for this purpose. MRPP has been applied to the study of the electrochemical behaviour of magnesium in aqueous... | 18,964,504 |
Determination of the sum of rare-earth elements by flow-injection analysis with Arsenazo III, 4-(2-pyridylazo)resorcinol, Chrome Azurol S and 5-bromo-2-(2-pyridylazo)-5-diethylaminophenol spectrophotometric reagents. | The reactivity of Arsenazo III, Chrome Azurol S in the presence of cetyltrimethylammonium or cetylpyridinium bromide, 4-(2-pyridylazo)resorcinol and 5-bromo-2-(2-pyridylazo)-5-diethylaminophenol with various rare-earth elements (REE) has been studied and the optimum conditions have been established for the spectrophoto... | 18,964,509 |
Determination of borate ion-pair stability constants by potentiometry and non-approximative linearization of titration data. | Borate anions, B(OH)(-)(4), are known to associate with alkali and alkaline-earth metal cations in sea-water. The borate cation ion-pairs are of the general form MB(OH)((n-1)+)(4), where M(n+) is the cation. In this work, the cation borate stability constants (K*(MB)) have been evaluated for Na(+), Li(+), Mg(2+), Ca(2+... | 18,964,511 |
The influence of atomization pressure on the behaviour of aluminium in electrothermal atomic-absorption spectrometry. | Pressurized atomization in argon purge gas considerably enhances the peak area in AAS determination of aluminium, owing to the decrease in the diffusion rate of atoms with increasing pressure. If lower heating rates are used, the diffusional loss mechanism becomes more important. Thus pressure then has an even more pro... | 18,964,541 |
HPLC separation of heterocyclic beta-diketonates of actinide, lanthanide and transition metals. | Liquid-chromatography conditions for the separation of neutral chelates of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with transition metals, lanthanides and actinides have been established. The use of reverse-phase liquid chromatography, instead of ion-exchange, is a novel approach for actinide separation. The high mola... | 18,964,552 |
Determination of two metals from a single potentiometric titration curve The application of two indicator electrodes. | The advantages of applying two indicator electrodes in complexometric potentiometric multicomponent titration are shown by means of simulated titration curves. Two measurement arrangements have been considered, one in which the indicator electrodes are directly connected to a voltmeter and the other in which the electr... | 18,964,554 |
Analysis of mixtures of purines and pyrimidines by first- and second-derivative ultraviolet spectrometry. | Zero-order, first-derivative and second-derivative ultraviolet absorption spectra of a series of purines, pyrimidines and their binary mixtures in aqueous solution have been recorded at 298 K. It is shown that second-derivative spectra can be used for the identification of eight mixtures of purines and pyrimidines. Sev... | 18,964,565 |
A PVC-coated carbon rod ion-selective electrode for thallium and its application to the analysis of rocks and minerals. | A new Tl(III) ion-selective electrode prepared by coating a graphite rod with a PVC membrane has been made and investigated. The optimum membrane composition is Butylrhodamine B-TlCl(-)(4) 5 mg, chlorobenzene 0.1 ml, dioctyl phthalate 0.4 ml, PVC 0.17 g. The electrode exhibits Nernstian response to Tl(III) over the con... | 18,964,574 |
Separation of selenium(IV) and tellurium(IV) from mixtures by extraction chromatography with trioctylphosphine oxide. | The reversed-phase extraction chromatographic separation of selenium(IV) and tellurium(IV) from several elements with trioctylphosphine oxide as extractant is reported. Selenium was extracted from 6M hydrochloric acid containing 7M lithium chloride was stripped with 4M hydrochloric acid, and tellurium was extracted fro... | 18,964,576 |
A rapid algorithm for solution of the equations of multiple equilibrium systems-RAMESES. | The solution of systems of equilibrium is an important though commonplace operation, rendered difficult by non-linearity. Previous methods of numerical solution have suffered from slow convergence, unreliability, and inefficient structure. An algorithm, RAMESES, is presented in matrix algebra terms, which is both simpl... | 18,964,599 |
Metal complexes of 1-oxa-4,7,10-triazacyclododecane-N,N',N''-triacetic acid. | The macrocyclic complexone 1-oxa-4,7,10-triazacyclododecane-N,N',N''-triacetic acid (cODTA) has been synthesized and its protona constants, stability constants of metal complexes and enthalpy changes for the formation of alkaline-earth complexes have been determined. Although it is not so powerful a complexing agent as... | 18,964,608 |
Derivative ultraviolet-visible region absorption spectrophotometry and its analytical applications. | Theoretical aspects, instrumental devices and analytical applications of derivative ultraviolet-visible region absorption spectrophotometry are reviewed. | 18,964,610 |
Examination of guanosine and xanthosine nucleotides by HPLC and electrochemical detection. | The suitability of electrochemical detection (ECD) following HPLC separation of guanosine, xanthosine and adenosine nucleotides has been evaluated. Separation of five monophosphates of guanosine was achieved by using a reversed-phase column; di- and triphosphates have also been separated from monophosphates. Adenosine ... | 18,964,643 |
Catalytic-adsorptive stripping voltammetric measurements of hydrazines. | Hydrazine compounds can be determined by voltammetry, based on their hydrogen catalytic wave in formaldehyde-platinum-sulphuric acid media. Adsorption of the platinum-formazone complex on the hanging mercury drop electrode enhances the sensitivity, allowing convenient measurement of micromolar and submillimolar concent... | 18,964,656 |
A new method for the iodometric determination of sulphoxides. | A method is described for determination of sulphoxides through their reaction with iodide in a trifluoroacetic acid/acetone medium to produce iodine, which is then titrated with thiosulphate. | 18,964,657 |
Solid state chemical ionization for characterization of organic compounds by laser mass spectrometry. | A new technique involving the addition of a compound to the analyte to serve as a source of "reagent" ions has been developed for negative-ion laser mass spectrometry. This "solid state chemical ionization" leads to ions characteristic of the analyte, owing to ion-molecule reactions between the "reagent" ion and the ne... | 18,964,680 |
Strategies for the reversible immobilization of enzymes by use of biotin-bound anti-enzyme antibodies. | Glucose oxidase (E.C. 1.1.3.4) is reversibly immobilized in a reactor coupled to a flow-injection analysis system using an immunological reaction. The antibody used is irreversibly immobilized on the reactor support by an avidin-biotin linkage. The bond between avidin and biotin is nearly irreversible under normal elut... | 18,964,697 |
Temperature effects on the solid-matrix luminescence properties of 4-phenylphenol adsorbed on filter paper. | Experimental values of fluorescence quantum yield, phosphorescence quantum yield, and phosphorescence lifetime were obtained at temperatures from 23 degrees to -180 degrees for 4-phenylphenol adsorbed on filter paper. From the experimental values, rate constants for phosphorescence and radiationless transition from the... | 18,964,707 |
Determination of zirconium in steels. | The determination of zirconium in the range 0.01-0.20% is required for some special alloy steels. A method has been developed, based on initial removal of iron as its chloro-complex by extraction with methyl isobutyl ketone, followed by further extraction after addition of potassium thiocyanate, and determination of th... | 18,964,725 |
Selective ion-exchanger behaviour of neutral carrier ion-selective electrode membranes. | Radiotracer experiments confirm that neutral carrier ion-selective electrodes made from plasticized PVC are low-capacity selective ion-exchangers. The ion-exchange selectivity is closely correlated to potentiometric selectivity. | 18,964,726 |
Mixed reagents in multicomponent flow-injection analysis Simultaneous determination of iron and copper in blood serum with mixed bathocuproinedisulphonate and bathophenanthrolinedisulphonate or ferrozine. | Mixtures of 0.6mM bathocuproinedisulphonate (BC) and 0.2mM bathophenanthrolinedisulphonate (BP) or 2mM BC and 0.2mM ferrozine (FZ) were used for a rapid determination of iron and copper in deproteinated blood serum in the presence of 0.1M formate buffer (pH 3.5), 10mM ascorbic acid and 0.3M trichloroacetic acid, by two... | 18,964,739 |
Determination of acriflavine, rivanol, Acridine Orange, Acridine Yellow and proflavine by a catalytic photokinetic method. | A fast and sensitive photokinetic method for the determination of acriflavine, rivanol, Acridine Orange, Acridine Yellow and proflavine is described. It is based on the rate of photoreduction of methylviologen in the presence of EDTA, sensitized by these diaminoacridines. The rate is monitored spectrophotometrically by... | 18,964,758 |
Estimation of kinetic parameters from thermochemical data. | A method is described by which kinetic parameters may be calculated from the measured temperature changes caused by the heat produced during a chemical reaction. An isoperibol titration calorimeter with an ampoule-breaking facility is used to obtain the temperature data. The temperature changes resulting from the react... | 18,964,761 |
Ion flotation behaviour of thirty-one metal ions in mixed hydrochloric/nitric acid solutions. | The ion flotation of 31 metal ions in hydrochloric/nitric acid solution with the cationic surfactant cetylpyridinium chloride was investigated. A 25-ml portion of 0.27-2.87 x 10(-4)M metal ion and 1.8-6.0 x 10(-4)M cetylpyridinium chloride solution in 0.17-3.4M acid mixture ([HCl]:[HNO(3)] = 2.4:1) was subjected to flo... | 18,964,771 |
Second derivative spectrophotometric determination of iron by extraction of the ferroin-perchlorate ion-association complex into mesityl oxide. | A highly selective and sensitive second-derivative spectrophotometric determination of iron is based on the extraction of the ferroin-perchlorate ion-association complex into mesityl oxide. A linear calibration graph is obtained for iron in the range 0.5-50 mug in 100 ml of original aqueous phase, with a detection limi... | 18,964,786 |
Reactivity of the cadmium ion in concentrated phosphoric acid solutions. | The solvation transfer coefficients which characterize the changes of ion reactivity with phosphoric acid concentration have been calculated for cadmium from the constants of the successive chloride complexes, and for silver and diethyldithiophosphate from potentiometric measurements. They evidence the strong desolvati... | 18,964,794 |
Preparation, composition and structure of some nickel and zinc ferrocyanides: Experimental results. | Several methods have been used for preparation of nickel and zinc ferrocyanides: precipitation, growth in a gel and a new method based on growth on a solid alkali-metal ferrocyanide. The granulometry, morphology, composition and structure of the compounds were studied. Only the last method of preparation gives products... | 18,964,798 |
The uranyl-chloro-substituted benzoic acid-rhodamine b-benzene extraction system. | Of the chloro-substituted benzoic acids, the 2-chloro and 2,4-dichloro compounds yield higher effective molar absorptivities than benzoic acid does in the Rhodamine B-benzene extractive spectrophotometric procedure for determination of uranium(VI). Carbonyl compounds (especially acetone) in the organic phase enhance th... | 18,964,850 |
Stripping voltammetry of silver(I) with a carbon-paste electrode modified with thiacrown compounds. | The accumulation behaviour and stripping voltammetry of silver(I) was investigated with a carbon-paste electrode modified with a thiacrown compound. Silver could be accumulated at the electrode in the absence of an applied potential by immersing the electrode in a solution of sodium perchlorate containing silver(I), th... | 18,964,860 |
Adsorptive voltammetric determination of copper as its nioximate complex. | A sensitive and selective stripping voltammetric ultratrace determination of copper is described, based on adsorptive accumulation of the cu(II)-nioxime complex on the surface of a hanging mercury drop electrode, followed by the reduction of the adsorbed complex during the cathodic scan. The analytical conditions for t... | 18,964,876 |
Effect of soluble calcium on the determination of the labile metal content of sediments with ion-exchangers. | Equilibration of sediments with cation-exchangers results in a transfer of loosely bound labile metal species to the exchanger phase. Dissolution of the matrix is also promoted and selectivity rules suggest that some of the cations released (particularly Ca) could effectively compete with metal ions for exchange sites.... | 18,964,894 |
Use of a spectrally segmented photodiode-array spectrometer for inductively coupled plasma atomic-emission spectroscopy Examination of procedures for the evaluation of detection limits. | The utility of a spectrally segmented photodiode array spectrometer was examined by using inductively coupled plasma atomic-emission spectrometry (ICP-AES). The spectrometer used in this study is capable of high resolution (reciprocal linear dispersion of approximately 0.08 nm/mm at 300 nm) over a wide spectral range (... | 18,964,913 |
Determination of tellurium in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separations by iron collection and xanthate extraction. | A method for determining approximately 0.01 mug/g or more of tellurium in ores, concentrates, rocks, soils and sediments is described. After sample decomposition and evaporation of the solution to incipient dryness, tellurium is separated from > 300 mug of copper by co-precipitation with hydrous ferric oxide from an... | 18,964,927 |
Electrochemical behavior of marcellomycin at lipid-modified carbon-paste electrodes. | A lipid-modified carbon-paste electrode is prepared by mixing phospholipids with the carbon-paste matrix. The resulting electrodes have polar head-groups which allow interactions with positively charged drugs and improved preconcentration/extraction steps. The accumulation of the antitumor drug, marcellomycin, is enhan... | 18,964,932 |
A new spectrophotometric method for quantitative multicomponent analysis resolution of mixtures of salicylic and salicyluric acids. | A new spectrophotometric method for resolving binary mixtures is proposed. The method is based on use of the first derivative of the ratios of spectra. The absorption spectrum of the mixture is obtained and the amplitudes at appropriate wavelengths are divided by the corresponding amplitudes in the absorption spectrum ... | 18,964,949 |
Elemental analysis of high-purity solids by mass spectrometry. | The applications of mass spectrometry in the determination of trace elements in some of the high-purity solid materials used in modern technology are reviewed. | 18,964,953 |
HPLC determination of niridazole. | A high-performance liquid chromatographic method has been developed for the determination of niridazole in bulk form and in pharmaceutical dosage form. A reversed-phase system, based on an octadecylsilane-bonded stationary phase and a 60:40 v/v methanol/water mobile phase, is used. The detector response at 370 nm is li... | 18,964,970 |
Chelating polymers and related supports for separation and preconcentration of trace metals. | This review is concerned mainly with the applications of chelating polymeric resins for the separation and concentration of trace metals from oceans, rivers, streams and other natural systems. Commercially available resins, specially prepared polymers and a selection of other sorbents are described and their uses outli... | 18,964,972 |
Heterocyclic dithiophosphates as analytical reagents Indirect extraction-spectrophotometric determination of silver in copper concentrates and ores. | The proposed method is based on the exchange reaction between the complex of copper(II) with 4,7-dimethyl-2-thiol-2-thion-1,3,2-dioxophosphorinan (DOPh(III)) in toluene and an aqueous solution of silver(I). The decrease in the absorbance of the Cu(DOPh(III))(2) solution is proportional to the silver(I) concentration fo... | 18,964,974 |
Computational studies of the chiral separations of three N-acyl-1-aryl-1-aminoethanes on an (R)-N-dinitrobenzoylphenylglycine stationary phase. | The chiral chromatographic separations of three N-acyl-1-aryl-1-aminoethanes on silica modified with (R)-N-dinitrobenzoylphenylglycine-N'-propylamide have been modeled by use of molecular mechanics. Formyl groups were substituted for the nitro groups, and a methyl group was tested as a replacement for the propyl group.... | 18,964,986 |
Spectrophotometric determination of trace sulphate in rain and snow after preconcentration with 2-aminoperimidine on a membrane filter. | A simple and precise preconcentration technique, based on collecting a precipitate on a membrane filter and dissolving the filter and precipitate in an organic solvent, has been applied to the spectrophotometric determination of trace sulphate in rain and snow. The sulphate is precipitated with 2-aminoperimidine and th... | 18,964,991 |
A study of electrodes used in controlled-potential electrolysis of metal ions. | Various electrodes used in controlled-potential electrolysis of metal ions are discussed: (1) a double-junction saturated calomel reference electrode with sodium formate as bridge electrolyte; (2) an auxiliary electrode made by winding platinum wire on a Teflon cylinder; (3) a working electrode made of tantalum gauze. ... | 18,965,001 |
A review of pH measurement at high temperatures. | Measurement of pH in aqueous solutions at up to 300 degrees and 150-300 bar is reviewed. Potentiometric membrane electrodes are identified as the sensors giving the most immediate hope of being practical. Zirconia membranes work well above 200 degrees and in alkaline solution, whereas glass membranes are best up to 150... | 18,965,019 |
Trace measurements of colchicine by adsorptive stripping voltammetry. | A highly sensitive voltammetric method for trace measurements of the alkaloid colchicine is described. The method is based on the controlled adsorptive accumulation of the drug at the hanging mercury drop electrode, followed by voltammetric determination of the surface species. The adsorptive stripping response is eval... | 18,965,020 |
Voltammetric determination of linuron at a carbon-paste electrode modified with sepiolite. | The determination of linuron by differential pulse voltammetry with a carbon-paste electrode modified with 20% w/w sepiolite has been studied. The linuron is preconcentrated under open-circuit conditions at pH 2.0. With 0.01M potassium nitrate at pH 1.7 in the measurement cell, a sweep rate of 30 mV/sec and a pulse amp... | 18,965,021 |
An amperometric enzyme electrode for the determination of 3alpha-hydroxysteroids. | An enzyme electrode for quantifying the total content of 3alpha-hydroxysteroids is described. 3alpha-Hydroxysteroid dehydrogenase (E.C. 1.1.1.50) was immobilized on the surface of glassy-carbon and low-temperature isotropic-carbon electrodes by intermolecular cross-linking with bovine serum albumin and glutaraldehyde. ... | 18,965,022 |
Spectrophotometric determination of some dithiocarbamates. | A procedure has been developed for the determination of six dithiocarbamates [sodium dimethyldithiocarbamate (dibam), sodium diethyldithiocarbamate (NaDDC), tetramethylthiuram disulphide (thiram), zinc dimethyldithiocarbamate (ziram), sodium N-methylpiperazinecarbodithioate and potassium morpholine-4-carbodithioate] in... | 18,965,097 |
Microband electrodes fabricated by screen printing processes: Applications in electroanalysis. | A novel method for the simple and cheap manufacture of microband and multiple microband electrodes is described. The construction technique is based entirely on the screen printing of the surface of alumina tiles with conducting and insulating ink materials. The range of potentials over which the electrodes may be used... | 18,965,101 |
Amperometric detection at a carbon-fibre array ring/glassy-carbon disk electrode in a wall-jet cell. | A wall-jet cell incorporating a carbon fibre array ring/glassy-carbon disk electrode has been constructed, and characterized by the cyclic voltammetry and flow-injection techniques. The ring (composed of several microdisks) and glassy-carbon disk electrode, can be used separately for different purposes, e.g., detection... | 18,965,107 |
On-line photo-oxidation for the determination of organoarsenic compounds by atomic-absorption spectrometry with continuous arsine generation. | A method has been developed for on-line conversion of organoarsenicals into arsenate, which is readily detected by atomic-absorption spectrometry with continuous arsine generation. The photoreactor consists of a mercury lamp wrapped with 5 m of PTFE tubing (0.5 mm i.d.). The photo-oxidation conditions were optimized, w... | 18,965,123 |
On-line monitoring of chloramine reactions by membrane introduction mass spectrometry. | Membrane introduction mass spectrometry has been applied to on-line monitoring of the reaction of monochloramine with hydrogen chloride. The detection limit for monochloramine introduced by a sheet-membrane direct-insertion probe and measured by electron impact ionization and selected ion detection was found to be 0.7 ... | 18,965,127 |
Spectrophotometric determination of nickel in vegetable oil with ammonium 2-amino-1-cyclohexene-1-dithiocarboate. | The reaction between nickel and ammonium 2-amino-1-cyclohexene-1-dithiocarboate in aqueous acetone medium at pH 3.0-8.0 results in a stable dark red complex. The ratio of reagent to nickel in the complex is 2:1 and the formation constant is 7.38 +/- 0.12 x 10(10). Beer's law is obeyed up to 4 microg/ml nickel at the ab... | 18,965,133 |
X-ray powder diffraction data for nine analgesics. | X-Ray powder diffraction data for nine analgesics have been obtained by using a powder diffractometer. The results obtained by using the McCreery and Byström-Asklund methods of sample loading were averaged and tabulated in terms of the lattice spacings and the relative line intensities. Data from powder camera films we... | 18,965,134 |
Determination of aminosaccharides by high-performance anion-exchange chromatography with pulsed amperometric detection. | High-performance anion-exchange chromatography (HPAC) was used for the determination of aminosaccharides in microbial polymers, chitin, animal waste, sewage sludge, plant residues and soil. The aminosaccharides, galactosamine, mannosamine and glucosamine were separated on a strong anion-exchange column with 1OmM sodium... | 18,965,136 |
Determination of metal ions by liquid chromatographic separation of their 2-acetylpyridine-4-ethyl-3-thiosemicarbazone chelates. | A new thiosemicarbazone was prepared, characterized, and used as a complexing reagent for the chromatographic separation and determination of metal complexes by reverse-phase HPLC. The reagent was sufficiently soluble in methanol-water solutions for metal ions to be complexed in this aqueous organic phase, without need... | 18,965,137 |
Accuracy in the precise coulometric titration of ammonia and ammonium ion with electrogenerated hypobromite. | A precise and accurate method in which ammonia and ammonium ions are coulometrically titrated with electrogenerated hypobromite was studied. Through the measurement of the current efficiency for generating hypobromite and the dependencies of titration results on electrolysis current and delay time between sampling and ... | 18,965,161 |
Trace measurements of rhodium by adsorptive stripping voltammetry. | A sensitive stripping voltammetric procedure for quantifying rhodium is described. The complex of rhodium with chloride ions is adsorbed on the hanging mercury drop electrode, and the reduction current of the accumulated complex is measured during a negative-going scan. Cyclic voltammetry is used to characterize the in... | 18,965,175 |
The synthesis of some lipophilic tetra-arylborates for use in membrane electrode preparation. | Synthetic methods for preparing four lipophilic tetra-arylborates considered suitable candidates for use in membrane electrodes are described. Qualitative precipitation tests were performed with several cations. The sodium salts of the four tetra-arylborates were found to have limited stability but the cesium salts wer... | 18,965,176 |
Determination of cadmium, lead and copper in water samples by flame atomic-absorption spectrometry with preconcentration by flow-injection on-line sorbent extraction. | Cadmium, lead and copper were determined in synthetic sea-water, drinking water and the NBS 1643b Trace Elements in Water standard reference material at mug/l. levels by flame atomic-absorption spectrometry after on-line preconcentration by sorbent extraction with a flow-injection system. Bonded silica with octadecyl f... | 18,965,193 |
Catalytic kinetic determination of ultratrace amounts of ruthenium(III) based on the oxidation of benzylamine by alkaline hexacyanoferrate(III). | A kinetic method is proposed for the determination of ruthenium(III) by means of its catalytic effect on the oxidation of benzylamine by hexacyanoferrate(III) in alkaline medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of hexacyanoferrate(III) at 420 nm. Under the opt... | 18,965,195 |
On the application of the Dumas technique for the determination of nitrogen in refractory nitrides. | The classical Dumas apparatus has been modified. The generally recommended oxidants CuO and V(2)O(5), were found to give relatively high blank values and were therefore replaced by Cu(2)O. The preparation of the Cu(2)O is described. It is an exceptionally suitable oxidant for the Dumas analysis of the Group Va nitrides... | 18,965,201 |
Kinetic determination of selenium, based on inhibition of the Pd(II)-catalysed reaction between pyronine G and hypophosphite. | A new kinetic method for determination of selenium is based on its inhibitory effect on the Pd(II)-catalysed reaction between Pyronine G and hypophosphite. Under the optimum experimental conditions (6 x 10(-5)M Pyronine G, 0.4M hypophosphite, 0.4 mug/ml Pd(II), pH 2.8, temperature 22.0 +/- 0.2 degrees ), Se can be dete... | 18,965,205 |
Determination of molybdenum by atomic-absorption spectrometry after separation by 5,5'-methylenedisalicylohydroxamic acid extraction and further reaction with thiocyanate and tin (II). | A method is described for the determination of molybdenum down to the microgram level, in samples of soil, steels, fertilizers and pharmaceuticals. After attack with acids, this element is separated from matrix elements by extraction of its 5,5'-methylenedisalicylohydroxamic acid (MEDSHA) complex from 4M hydrochloric a... | 18,965,215 |
Determination of copper at ng levels by in-line preconcentration and flow-injection analysis coupled with flame atomic-absorption spectrometry. | Oxine/formaldehyde/resorcinol and oxine/formaldehyde/hydroquinone resins have been synthesized and their physicochemical properties studied. Conditions were optimized for the preconcentration of copper by batch extraction and column chromatography with the resins. A flow-injection analysis (FIA) manifold was constructe... | 18,965,216 |
A highly sensitive colour reaction for chromium(VI) with the iodide-basic xanthene dye-pva system. | A highly sensitive spectrophotometric method has been developed for determination of chromium(VI), based on oxidation of I(-) to I(-)(3) in acid medium, then formation of a 1:1 ion-association compound of I(-)(3) with a basic xanthene dye in the presence of poly(vinyl alcohol). The molar absorptivity is 1.79 x 10(5) 1.... | 18,965,224 |
Comparative study of a beenakker cavity and a surfatron in combination with electrothermal evaporation from a tungsten coil for microwave plasma optical emission spectrometry (MIP-AES). | Microwave induced plasmas, sustained in a Beenakker resonator and a surfatron, respectively, are used to excite vapours released by electrothermal evaporation of solutions from a tungsten coil. The analytical figures of merit of AES for two easily volatilized elements (Cu, Cd) are compared for argon MIP operated in the... | 18,965,230 |
The determination of lead in total suspended air particulates by x-ray fluorescence spectroscopy. | A method has been developed for the measurement of lead in air particulates collected on glass fiber filter paper with wavelength-dispersive x-ray fluorescence spectroscopy (WDXRF). Analyses conducted by both WDXRF and an EPA-approved procedure that employs acid sonication followed by analysis of the extract by atomic-... | 18,965,250 |
Simultaneous determination of iron(III) and vanadium(V) by use of a kinetic-spectrophotometric and rapid mixing flow system. | The quantitative spectrophotometric determination of V(V) by its catalytic effect on the oxidation of chromotropic acid [the disodium salt of 4,5-dihydroxynaphthalene-2,7-disulphonic acid (CS)] by potassium bromate has been adapted to a flow system employing a rapid sample and reagent introduction manifold, in which va... | 18,965,277 |
Potentiometric determination of trace silver based on the use of a carbon paste electrode. | A carbon paste electrode used as a sensor for silver has been developed and electrode response characteristics have been investigated. The electrode exhibits linear response to the logarithm of the concentration of silver from 5 x 10(-7)M to 1 x 10(-2)M, with a response slope of 63 +/- 2 mV. The detection limit accordi... | 18,965,282 |
Statistical optimisation applied to the spectrophotometric study of the tolmetin-Fe(III) complex. | Tolmetin sodium has been examined and determined from dosage forms as its Fe(III) complex and the method has been optimized by statistical optimization. | 18,965,308 |
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