title stringlengths 0 1.13k | abstract stringlengths 1 15.7k | PMID int64 22 36.5M |
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Determination of indium by hydride generation and atomic-absorption spectrometry. | Conditions are presented for the determination of indium by atomic-absorption spectrometry following hydride generation. Indium hydride produced by addition of sodium borohydride to a solution of indium in 3M hydrochloric acid is flushed with argon into an electrically heated silica tube. The mass of indium giving 1 % ... | 18,963,177 |
Effect of cationic surfactant on the formation of ferron complexes. | In the spectrophotometric determination of aluminium and iron with ferron (7-iodo-8-quinolinol-5-sulphonic acid, H(2)L), the addition of cationic surfactants greatly improves the linearity of the calibration curve and widens the useful pH range. The effect of cetyltrimethylammonium chloride (CTMAC) on the stepwise stab... | 18,963,188 |
Determination of molybdenum by extraction of its thiocyanate into ethyl methyl ketone. | A simple, sensitive and selective spectrophotometric method for determination of molybdenum is described. A solution containing 100 mug of Mo in 2.5M hydrochloric acid is treated with ascorbic acid and ammonium thiocyanate and after standing for 8 min is shaken with an equal volume of ethyl methyl ketone for 30 sec. Th... | 18,963,196 |
Selective extraction of metal ions associated with humic acids. | The ability of a range of electrolyte solutions to release metal ions (Cu, Pb, Cd, Zn) presorbed on two samples of humic acid has been investigated. Though treatment with mineral acid or a chelating agent released a high proportion of the retained metal ion, recoveries were never total. Concentrated salt solutions disp... | 18,963,227 |
Validation of the sulphur concentration of selected iron-base NBS standard reference materials by isotope-dilution spark-source mass-spectrometry. | An isotope-dilution spark-source mass-spectrometric procedure has been developed for the accurate determination of sulphur in iron-base alloys. Dissolution in a sealed tube is used to prevent volatilization losses and to effect isotope equilibration. Application of this technique to the re-analysis of existing NBS Stan... | 18,963,243 |
Biacetyl monoxime glycinimine as a selective reagent for palladium and nickel. | Biacetyl monoxime glycinimine is proposed as a new reagent for the selective gravimetric and extractive photometric determination of Pd(II) and Ni(II). The reagent forms yellow and rose-red water-insoluble complexes with Pd (pH 0.5-5.5) and Ni (pH 5.0-11.2) respectively. The complexes can be used for direct gravimetric... | 18,963,268 |
Purification of analytical reagents. | Considerable progress in the purification of reagent chemicals has been made during the past decade. Improved or newly developed methods and their application for producing analytical reagents of highest purity are described. Various techniques are evaluated critically with respect to convenience and efficiency of use ... | 18,963,277 |
[Not Available]. | This paper describes a low-cost 6809 microprocessor-based system designed for the acquisition, analysis, preprocessing and recording of electrochemical kinetic data. Determination of second-order rate constants involves a preliminary calculation of a characteristic parameter of the electro-chemical system investigated,... | 18,963,289 |
Elution and spectrophotometric determination of gold after its separation from non-volatile platinum metals by column extraction chromatography. | Mixtures of gold(III) and iridium(IV) were separated by column extraction chromatography on silica treated with a tri-n-octylamine (TOA) salt. A mixture 2.25M in hydrochloric acid and 5M in nitric acid was used for elution of iridium. Gold was eluted together with the TOA salt by acetone, and after evaporation of the a... | 18,963,301 |
Iodometric standardization and biamperometric determination of iridium(IV). | Ir(IV) in the concentration range 0.4-0.8 g/l. can be easily determined iodometrically with 0.01M thiosulphate (starch as indicator). The relative standard deviation is 0.2-0.3%. When other coloured ions are present, biamperometric detection is recommended. | 18,963,305 |
Silica gel with adsorbed Adogen 464 as an analytical sampling tool for anions. | A solid extractant made with the liquid anion-exchanger Adogen 464 supported on silica gel has been prepared and its potential as a resin-like exchange material has been evaluated. In acid media it furnishes a ready available, inexpensive tool for recovery of anionic metal complexes as well as simple anions and for eli... | 18,963,310 |
An algorithm for reducing storage requirements in computer calculation of chemical equilibria. | An algorithm for storage of stoichiometric coefficients of the possible complexes and solids in a multi-component system of metals and ligands is described, along with FORTRAN code for its implementation. The proposed algorithm results in considerable saving in storage over the conventional use of a two-dimensional arr... | 18,963,319 |
Determination of silicon by an indirect atomic-absorption method using carbon-rod electrothermal atomization. | An indirect procedure has been developed for the determination of trace amounts of silicon by atomic-absorption with carbon-rod electrothermal atomization. After dissolution, the silicon is extracted as silicomolybdic acid into a mixture of diethyl ether and pentan-1-ol (5 + 1). The co-extraction of excess of molybdate... | 18,963,328 |
Chemical and instrumental analysis of ferrites. | More than thirty years since the manufacture of the first commercial ferrites, research and development efforts continue to produce ferrites with enhanced performance and new applications. Analytical chemistry has maintained a substantial role in the ferrite industry in the characterization of both raw materials and pr... | 18,963,365 |
Spectrophotometric determination of trace amounts of selenium with 4,5,6-triaminopyrimidine. | 4,5,6-Triaminopyrimidine reacts in acidic aqueous media with selenium (IV) to give a piazselenol which has an absorption maximum at 362 nm with a molar absorptivity of 1.72 x 10(4) 1.mole(-1).cm(-1). The compound is stable but not extractable into non-polar solvents. The calibration graph is linear up to 10 ppm of sele... | 18,963,385 |
Application of cellulose anion-exchangers to separation of palladium from platinum or iridium with glycine as complexing agent and atomic-absorption spectrometry for detection. | The use of glycine as complexing agent for chromatographie separation of palladium from platinum, or palladium from iridium, on cellulose anion-exchangers has been investigated and found possible over a wide range of concentration ratios. The method can be used for analysis of Pd-Ir alloys. The nature of the complexes ... | 18,963,400 |
Titrimetric microdetermination of uric acid and thioglycollic acid by amplification reactions. | A simple amplification method for determination of 0.05-2 mg of uric acid or thioglycollic acid has been worked out. It depends on iodine oxidation of the uric acid or thioglycollic acid solutions, removal of the excess of iodine, oxidation of the resulting iodide with bromine, and iodometric titration of the resulting... | 18,963,429 |
Selective complexometric determination of mercury with thiocyanate as masking agent. | A method is proposed for selective complexometrie determination of mercury, thiocyanate being used as masking agent. An excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate, Xylenol Orange or Methylthymol Blue being used as indicator. Thiocyanate is then added to decompose the mercury-ED... | 18,963,430 |
Rapid and selective chelatometric titration of zinc in non-ferrous alloys. | A rapid titrimetric method for the determination of Zn (5%) in zinc, aluminium and copper alloys is proposed. It is based on the chelation of Zn(II) with HEDTA as titrant in an ethanolic aqueous medium. The end-point is detected with hydrazidazol, a new indicator developed in China. Up to at least 6% Mn in the alloy do... | 18,963,480 |
Solid-state halide ion-selective electrodes: studies of quaternary ammonium halide solutions and determination of surfactants. | The feasibility of using homogeneous membrane-type halide ion-selective electrodes in solutions containing cationic surfactant compounds was examined. The results established the applicability of these electrodes for monitoring halide ions in solution without interference by the surfactants. The data also provided a ba... | 18,963,482 |
Determination of thallium in lead salts by differential pulse anodic-stripping voltammetry. | The determination of trace levels of thallium in lead and lead salts by differential pulse anodic-stripping voltammetry has been made possible by using a surfactant as an electrochemical masking agent in addition to a complexing agent. In 0.2M EDTA at pH 4.5 as supporting electrolyte without surfactant, lead at concent... | 18,963,486 |
Critical examination of some common reagents for reducing selenium species in chemical analysis. | In an attempt to resolve apparently conflicting statements in the literature, a study has been made of the action of various reductants on selenium(VI) and selenium(IV). Chloride in hot non-oxidizing acid medium will reduce Se(VI) to Se(IV) but not further. Sulphur dioxide will reduce Se(IV) to Se, but has no effect on... | 18,963,515 |
Determination by hplc of trifluoroacetate levels in plasma and urine of patients anaesthetized with halothane. | A new method is described for determination of trifluoroacetic acid (TFA) in biological fluids. Optimum extraction is achieved by addition of 18-crown-6 ether and acidification of the sample. The 4-bromomethyl-7-methoxycoumarin derivatives of the carboxylic acid are prepared and a sample is subjected to HPLC. A linear ... | 18,963,555 |
Ion-pair extractions with 12-crown-4 and its analogues. | The complexing abilities of 12-crown-4 and its analogues have been investigated by using ion-pair extractions. A relationship exists between the type of substitution on the 12-crown-4 and the complexing ability and selectivity. Additionally, the selectivities vary according to the reagent concentrations. The compound 1... | 18,963,560 |
Study of high-voltage breakdown and material consumption in spark-source mass spectrometry and their significance in analytical applications. | The breakdown voltage has been found to be dependent on the gap width between the electrodes and on the melting point of the sample elements in spark-source mass-spectrometry (SSMS). The number of discharges per pulse train and the time required to reach the first discharge depend only on the chosen breakdown voltage. ... | 18,963,563 |
Investigation of the use of thermometric titrimetry for the determination of acidic substances in wine. | The use of thermometric titrimetry in the determination of acidic substances in red wine is described. The titration curve obtained in the thermometric titration of red wine with strong base presents two inflections. The stoichiometry corresponding to the first inflection presents good agreement with the so-called "tot... | 18,963,573 |
Binary data acquisition from instrumentation with BCD-coded output: a hardware converter and an example of the relative software control. | Simple hardware for conversion from BCD into binary code is described. The device is of low cost, performs a 16-bit conversion in a maximum time of 400 nsec, and is able to output the converted number to either an 8-bit or a 16-bit data bus. An example of the software necessary to perform data acquisition from a digita... | 18,963,586 |
Application of the deford and hume method modified for quasi-reversible and irreversible processes to the chelates of Bi(III) with azomethine derivatives of 2-benzoylpyridine. | The polarographic behaviour of the bismuth complexes of the oxime, hydrazone and thiosemicarbazone of 2-benzoylpyridine has been studied by differential pulse polarography. The DeFord and Hume method, modified for use with quasi-reversible and irreversible processes, has been applied for the calculation of the formatio... | 18,963,615 |
Background-current subtraction in voltammetric detection for flow-injection analysis. | A new approach for background-current subtraction for flow-injection systems using potential-scanning voltammetric detection is described. The method is based on recording voltamperograms while the sample and carrier solutions flow through the cell, and taking the difference as the net response for the sample. Backgrou... | 18,963,616 |
Extraction of catechol violet, chrome azurol S and eriochrome cyanine R with chloroform solutions of liquid anion-exchangers. | The extraction of Catechol Violet, Chrome Azurol S and Eriochrome Cyanine R with chloroform solutions of tri-n-octylamine (TOA), TOA hydrochloride and Aliquat 336 has been investigated. From the extraction isotherms, absorption spectra of the organic phases and dependence of the extraction coefficients on extractant co... | 18,963,620 |
Exchange equilibria between bicarbonate, carbonate, chloride and bromide on dowex 1 x 8. | The exchange reaction 2R(+)HCO(3)(2-) + CO(3)(2-) right harpoon over left harpoon R(2)(+) CO(3)(2-) + 2HCO(3)(2-) has been studied on Dowex 1 x 8 in the presence of bicarbonate solution in equilibrium with atmospheric carbon dioxide (open system). The experiments showed, as theory predicts, that the composition of the ... | 18,963,640 |
Spectrophotometric studies on ion-pair extraction equilibria of the iron(ii) and iron(III) complexes with 4-(2-pyridylazo)resorcinol. | The ion-pair extraction equilibria of the iron(II) and iron(III) chelates of 4-(2-pyridylazo)resorcinol (PAR, H(2)L) are described. The anionic chelates were extracted into chloroform with benzyldimethyltetradecylammonium chloride (QC1) as counter-ion. The extraction constants were estimated to be K(ex1)(Fe(II)) = [Q{F... | 18,963,641 |
Extraction of potassium p-nitrophenoxide with macrocyclic crown ethers and cryptands from aqueous medium into diverse organic solvents: a systematic evaluation. | A systematic study has been made of the extraction of potassium p-nitrophenoxide from aqueous medium into a number of organic solvents that are immiscible or partly miscible with water, in the presence of several macrocyclic crown ether and cryptand complexing agents. The efficiency of extraction varies extremely widel... | 18,963,655 |
Studies on extraction of indium by tributyl phosphate from thiocyanate solutions. | Indium can be quantitatively separated from a large number of elements which are usually associated with it, by extraction with 15% tributyl phosphate solution in kerosene from hydrochloric acid (pH 1)/0.5M potassium thiocyanate medium and stripping with 6M nitric acid. The equilibration takes 20 min. | 18,963,666 |
Determination of poly(oxyethylene) non-ionic surfactants by two-phase titration. | The solvent extraction of non-ionic surfactants with sodium hydroxide and tetraphenylborate has been studied, and a method developed for the determination of non-ionic surfactants by two-phase titration. A hydrophobic indicator system was used. The method is valid only when the concentration of anionic surfactant in th... | 18,963,667 |
Use of ammonium molybdate in the colorimetric assay of cephalosporins. | A colorimetric method for the determination of five cephalosporins (cefoxitin sodium, cefotaxime sodium, cephapirin sodium, cephalothin sodium and cephaloridine), based on the blue colour formed by reaction of the cephalosporins with ammonium molybdate, is described. The effects of reagent concentration and reaction co... | 18,963,668 |
Stable-isotope ratio analysis based on atomic hyperfine structure and optogalvanic spectroscopy. | Atomic hyperfine structures were measured for the Cu I transition at 5782 A by optogalvanic spectroscopy at high resolution, with a cw dye laser. Samples were electro-deposited on the demountable cathode of a home-made hollow-cathode lamp. By spectral deconvolution, the relative isotopic abundances of (63)Cu and (65)Cu... | 18,963,676 |
Influence of volatile hydride-forming elements on antimony determination by atomic-absorption spectrometry with hydride-generation. | A study was undertaken to determine the interfering effects of arsenic, bismuth, germanium, lead, selenium, tin and tellurium on trace determination of antimony by atomic-absorption spectrometry with hydride-generation. A 1% NaBH(4) solution was used as reductant and a small amount of oxygen was added to the hydrogen p... | 18,963,683 |
Determination of micro amounts of uranium by a molybdenum blue method. | A new and highly sensitive spectrophotometric method has been developed for the determination of micro amounts of uranium by a molybdenum blue method. The method is based on the observation that at low acidities uranium(IV) reduces ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the am... | 18,963,698 |
Determination of cerium in silicate rocks by electrothermal atomization in a furnace lined with tantalum foil Application to 19 international geological reference materials. | A 40-fold increase in sensitivity obtained by using a tantalum foil lining in a pyrolytically-coated graphite furnace permitted determination of low ppm levels of cerium in most silicate rocks. A preliminary preconcentration by oxalate and hydroxide co-precipitations was used before determination by use of a Varian GTA... | 18,963,724 |
Zinc and nickel ferrocyanides: preparation, composition and structure. | A review is given of work on nickel and zinc ferrocyanides during the period 1922-1983 with an emphasis on their compositions and structures in relation to the methods of preparation. | 18,963,739 |
Alkali-metal ion complexation with lariat ethers possessing a chromogenic group. | The extraction and complexation abilities of chromogenic alkyl crown-ether reagents were compared with those of their chromogenic benzo crown ether analogues. Improvements in the extraction efficiency and stability of the complexes were observed, and can be attributed to various factors such as increased lipophilic cha... | 18,963,740 |
Dissolution of geological material with orthophosphoric acid for major-element determination by flame atomic-absorption spectroscopy and inductively-coupled plasma atomic-emission spectroscopy. | An analytical procedure has been developed for the determination of major elements in geological material by both flame atomic-absorption spectrometry and inductively-coupled plasma atomic-emission spectrometry. Condensed phosphoric acid was used for the decomposition of 70 natural minerals containing sulphide, oxide, ... | 18,963,741 |
Spectrophotometric determination of zinc with phenylfluorone in the presence of hexadecylpyridinium bromide and pyridine. | Phenylfluorone reacts with zinc in the presence of hexadecylpyridinium bromide and pyridine to form a water-soluble red chelate. The absorption maximum of the chelate is at 585 nm and its absorbance is constant in the pH range 7.7-8.2. At this wavelength, Beer's law is obeyed up to 1.53 x 10(-5)M zinc. The sensitivity ... | 18,963,754 |
Determination of hormones by time-resolved fluoroimmunoassay. | Immunoassays based on europium labels and time-resolved fluorescence as the detection method, have been developed. The specific activity of the label is several orders of magnitude higher than that of radioactive labels. Consequently, the technique provides great potential, especially in the determination of analytes w... | 18,963,767 |
Immunoassays in aqueous two-phase systems. | Aqueous two-phase systems provide a novel and convenient method for separating bound from free fractions in a binding assay. The ease of automation of this type of procedure makes it particularly attractive for separations based on immobilized ligands or binders or on adsorbents. | 18,963,768 |
Perturbation of laboratory test results by analytical interferences and drug effects. | An account is given of ways in which drug treatment can influence the results of laboratory tests for certain species of clinical importance, and of methods of detecting such interferences or effects. | 18,963,771 |
Determination of the rare earths, yttrium and scandium in silicate rocks and four new geological reference materials by electrothermal atomization from graphite and tantalum surfaces. | An improved graphite furnace atomic-absorption method has been developed for the determination of Sc, Y and the rare-earth elements in silicate rocks and related materials. The method, which involves the separation of the lanthanides by ion-exchange followed by their determination by electrothermal atomization, with us... | 18,963,773 |
Computer control of microprocessor-based instruments by keypad emulation. | A keypad emulation method for controlling microprocessor-based instruments by laboratory microcomputers is presented. It is applicable to instruments that use "polled" keypad arrays; the instrument can be controlled by the laboratory computer or operated independently by manual keypad entry. To illustrate the approach,... | 18,963,782 |
Characteristics of industrial di(alkylphenyl)dithiophosphoric acids. | Instrumental and classical methods have been used to characterize some industrial di(alkylphenyl)dithiophosphoric acids. The (31)P-NMR chemical shifts of di(nonylphenyl)dithiophosphoric acid and its derivatives are summarized. | 18,963,798 |
Occurrence of consistent nM levels of phosphate in doubly demineralized and demineralized-distilled water. | A double demineralization system and a demineralization-distillation system operated over several months consistently delivered water that was approximately 30 nM in phosphate, as determined by a molybdenum blue spectrophotometric method. Silicate and hydrolysed polyphosphate in the water, and contaminants in the analy... | 18,963,799 |
Complexometric determination of citric acid with copper. | A method is presented in which citrate is determined by complexation with excess of copper(II), followed by back-titration with EDTA. Small amounts of citrate can be determined by this method in the presence of large amounts of most organic acids present in natural products. Interfering reductants are removed by treatm... | 18,963,814 |
[Not Available]. | The basic computer program MICMAC has been developed to fit equilibrium constants to various types of experimental data with a microcomputer. The program uses the very efficient Gauss-Newton-Marquardt algorithm for non-linear least-squares multiparametric refinement. Highly interactive, convenient to use and of modular... | 18,963,839 |
Sensitive flotation-spectrophotometric determination of gold, based on the gold(I)-iodide-methylene blue system. | The gold(I)-iodide-Methylene Blue (MB) system is suitable for flotation separation and spectrophotometric determination of gold. Under the optimum conditions [(MB(+))(AuI(2)(-))].3[(MB(+))(I(3)(-))] is formed, and floated with cyclohexane. The product is dissolved in methanol and its absorbance measured. The molar abso... | 18,963,845 |
Determination of sulpha-drugs with ion-selective membrane electrodes--II. | Two liquid-membrane electrodes, one sensitive to Cu(2+) and the other to Ag(+), were used for the determination of various sulpha-drugs with pK(a) > or = 6 (as the sodium salts) by potentiometric titration with CuSO(4) and AgNO(3). The construction and basic characteristics of these two electrodes are discussed. | 18,963,846 |
Spectrophotometric determination of silicon in silicates by flow-injection analysis. | A flow-injection spectrophotometric method has been developed for the accurate, continuous determination of silicon in silicate rocks. A rock sample solution is prepared by fusion with a 1:1 mixture of lithium carbonate and boric acid and subsequent dissolution of the cake in 1 M hydrochloric acid. The preparation tech... | 18,963,859 |
Etude par spectroscopie raman du chlorhydrate de cocaine. | Raman spectra of cocaine hydrochloride in the polycrystalline state and in saturated aqueous solutions have been recorded at room temperature from 0 to 4000 cm(-1) and at 9 K from 0 to 200 cm(-1) (only for the polycrystalline state). They show that cocaine can be characterized by the following proposed assignments. For... | 18,963,861 |
Contributions to the theory of catalytic titrations-II Precipitation and redox catalytic titrations. | Precipitation and redox catalytic titration curves, obtained by both volumetric and coulometric addition of the titrant, have been simulated, taking into account the equilibrium concentration of the catalyst during the titration. The influence of several factors on the shape of the simulated catalytic titration curves ... | 18,963,897 |
Geographic approaches to quantifying the risk environment: drug-related law enforcement and access to syringe exchange programmes. | The concept of the "risk environment"--defined as the "space ... [where] factors exogenous to the individual interact to increase the chances of HIV transmission"--draws together the disciplines of public health and geography. Researchers have increasingly turned to geographic methods to quantify dimensions of the risk... | 18,963,907 |
The behaviour of two types of copper ion-selective electrodes in different copper(II)-ligand systems. | The behaviour of two types of solid-state homogeneous sensors for copper(II), one based on pressed pellets of ternary CuAgSe and the other on thin-layer electroplated Cu(2-x)Se, in 12 different copper(II)-ligand systems, has been thoroughly investigated. Both electrodes exhibit anomalous behaviour when the ligands are ... | 18,963,923 |
Use of methyliminodiacetic acid bound to cellulose for preconcentration and determination of trace-metal cations. | Methyliminodiacetic acid immobilized on a cellulose support can be conveniently utilized for trace-metal uptake. Capacities and uptake yields as a function of pH have been evaluated for Pb(II), Cu(II), Mg(II), Ca(II), Cd(II), Zn(II), Co(II), Ni(II) and Hg(II) and the results compared with those predicted from the stabi... | 18,963,927 |
Multiparametric curve fitting--VIII: The reliability of dissociation constants estimated by analysis of absorbance-pH curves. | The program SPOPT estimates stability constants beta(pqr) and molar absorptivities epsilon(pqr) of all light-absorbing species M(p)L(q)H(r) by analysis of the absorbance-concentration (or absorbance-pH) curve. The program DCMINUIT estimates dissociation constants and molar absorptivities of protonated species. Both pro... | 18,963,929 |
N-chlorophthalimide as a new oxidant for direct titrations in aqueous acetic acid medium. | A stable new oxidimetric titrant, N-chlorophthalimide in anhydrous acetic acid, is proposed for direct titrations of a variety of simple and complex reductants such as As(III), Sb(III), Fe(II), ferrocyanide, iodide, ascorbic acid, hydroquinone, hydrazine, phenylhydrazine, benzhydrazide, isonicotinic acid hydrazide, sem... | 18,963,951 |
Analytical properties of 2-oximinodimedone dithiosemicarbazone. | The synthesis and analytical properties of 2-oximinodimedone dithiosemicarbazone are described. | 18,963,954 |
Separation of trans-1,2-cyclohexanediaminetetra-acetic acid chelates of bismuth(III), iron(III) and copper(II) by reversed-phase paired-ion chromatography. | Trans-1,2-cyclohexanediaminetetra-acetic acid (DCTA) chelates of bismuth(III), iron(III) and copper(II) have been separated by two techniques using reversed-phase paired-ion chromatography. In one, the chelates in aqueous solution were separated within 20 min on a 6.0 x 300 mm ERC-ODS column with 10(-2)M tetrabutylammo... | 18,963,960 |
Calculation of equilibrium constants from multiwavelength spectroscopic data-III Model-free analysis of spectrophotometric and ESR titrations. | Factor analysis of spectroscopic data is a well-known tool for the determination of the number of independent absorbing species in a series of mixtures. It has also been used for the reduction of the data-set in the calculation of equilibrium constants from multiwavelength data. The paper presents a new application of ... | 18,963,968 |
Spectrofluorimetric assay of tetracycline and anhydrotetracycline in combination. | Spectrofluorimetric methods are described for the assay of tetracycline (TC) and anhydrotetracycline (ATC) in combination, without prior separation. The interference from ATC in the TC assay has been corrected for by forming the aluminium complexes of both drugs and measuring the difference in fluorescence at 475 and 4... | 18,963,972 |
Minipol, a desk-computer program for refinement of protonation constants from differential-pulse polarographic data. | The program MINIPOL, designed to run on a desk-computer with 32 kbytes of memory, can calculate the optimum values of overall protonation constants and molar intensities of up to 8 species with composition H(XXX)L(rho), from differential-pulse polarographic data. | 18,963,974 |
Colorimetric determination of two fenamates in capsule dosage form. | The colorimetric determination of mefenamic acid and flufenamic acid with potassium ferricyanide in sodium hydroxide medium is described. The orange product is measured at 464 nm. The molar absorptivities are 1.9 x 10(3) and 2.9 x 10(3) 1.mole(-1).cm(-1) for mefenamic acid and flufenamic acid, respectively. The method ... | 18,963,983 |
Effect of cyclodextrin cavity size on sensitization of room-temperature phosphorescence of biacetyl. | The triplet-triplet energy-transfer reactions of several polynuclear aromatic compounds are enhanced to different degrees in alpha -,beta and gamma-cyclodextrin (CD) media when biacetyl is used as the acceptor species. The phosphorescence intensity of biacetyl increases as the size of the CD cavity increases. The CD ca... | 18,963,988 |
Postural and gait performance in children with attention deficit/hyperactivity disorder. | Up to 50% of children and adolescents with attention deficit/hyperactivity disorder (ADHD) exhibit motor abnormalities including altered balance. Results from brain imaging studies indicate that these balance deficits could be of cerebellar origin as ADHD children may show atrophy in those regions of the cerebellum ass... | 18,963,991 |
Extraction of manganese(II), iron(II), cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) into 1,2-dichloroethane with 4,7-diphenyl-1, 10-phenanthroline and perchlorate. | The extraction of the ion-association complexes formed by Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)-4,7-diphenyl-1, 10-phenanthroline (BP) chelates and perchlorate ions into 1,2-dichloroethane has been investigated. Extraction equilibrium for Mn(II), Cu(II), Zn(II) and Cd(II) is reached within 1 hr, but... | 18,964,002 |
Liquid-liquid extraction of univalent class b metal ions by the thiacrown compound 4'-picrylaminobenzo-1,4,8,11-tetra-thiacyclopentadec-13-ene. | A new thiacrown compound in which the picrylamino group is introduced as the chromogenic group, 4'-picrylaminobenzo-l,4,8,11-tetrathiacyclopentadec-13-ene (4'-PicNHBz-TTCP), has been successfully synthesized and its characteristics as an extracting and spectrophotometric reagent have been examined. This compound (HL) f... | 18,964,006 |
Reactions of nitrogen bases with nickel chelates of di-o-tolylcarbazone and di-o-tolylthiocarbazone. | The behaviour of nickel di-o-tolylcarbazonate and nickel di-o-tolylthiocarbazonate with organic nitrogen bases has been examined with a view to better understanding of the effect of different donor atoms in adduct formation. The adducts formed vary remarkably in composition and stability, and there are some interesting... | 18,964,009 |
Iridium in sea-water. | Iridium in sea-water has been measured (after isolation from the saline matrix by reduction with magnesium) by neutron bombardment, radiochemical purification and high-resolution gamma-ray spectroscopy. The concentration obtained in a Pacific coastal water was 1.02 +/- 0.26 x 10(-14) g per g of sea-water. At such extre... | 18,964,014 |
Humoral immunity to HIV-1: neutralisation and antibody effector functions. | Several features of HIV have frustrated efforts to develop a vaccine able to induce broadly neutralising antibodies. The enormous genetic diversity of HIV is a major factor, accompanied by the camouflaged nature of the envelope spike, upon which HIV depends for cellular entry and to which antibodies must bind to neutra... | 18,964,020 |
The (political) economics of antiretroviral treatment in developing countries. | Despite unprecedented international mobilisation to support universal provision of highly active antiretroviral therapy (HAART), national governments continue to play the key role in determining access to treatment. Whereas some AIDS-affected countries have performed as well as or better than expected given their level... | 18,964,022 |
Analytical applications of absorption spectroelectrochemistry at grazing incidence. | Analytical applications of spectroelectrochemistry are limited by the short path-length, in the absorbing medium, that can be produced with most light-beam/electrode configurations. This disadvantage is overcome for grazing incidence. A cell fitted with glassy-carbon electrodes and used in a conventional spectrophotome... | 18,964,032 |
Preconcentration of cobalt with N-(dithiocarboxy)sarcosine and amberlite xad-4 resin. | Cobalt reacts with N-(dithiocarboxy)sarcosine (DTCS) to form a 1:3 Co:DTCS complex which is so stable that after its formation no decomposition occurs even in 4M hydrochloric acid. The complex is sorbed on a column of Amberlite XAD-4 copolymer from an acidic solution and eluted with 10 ml of a 1:1:3 v v mixture of 1.0M... | 18,964,053 |
Simultaneous polarographic determination of cadmium and tellurium in electro-deposited cadmium telluride thin films. | A polarographic method has been developed for the simultaneous determination of cadmium and tellurium in thin-film cadmium telluride. The procedure involves dissolution of the film with concentrated nitric acid, which is subsequently removed by evaporation. The Cd(II) and Te(IV) waves are well separated at pH 10, but s... | 18,964,062 |
Trace determination of yttrium and some heavy rare-earths by adsorptive stripping voltammetry. | The interfacial and redox behaviour of rare-earth chelates with Solochrome Violet RS are exploited for developing a sensitive adsorptive stripping procedure. Yttrium and heavy rare earths such as dysprosium, holmium and ytterbrium can thus be measured at ng ml levels and below, by controlled adsorptive accumulation of ... | 18,964,091 |
A new method for the atomic-absorption determination of lead blended as lead alkyls in motor spirit. | The total lead present as tetraethyl-lead (TEL) and tetramethyl-lead (TML) in motor spirit is determined by atomic-absorption spectrometry after decomposition by extraction with a mixture of mercaptoacetic acid and nitrous acid in the presence of hydrochloric acid. | 18,964,099 |
Analytical investigations on cephalosporins--IV: application of Ellman's reagent. | The application of 5,5'-dithiobis(2-nitrobenzoic acid) (Ellman's reagent) for the determination of microgram quantities of various selected cephalosporins in aqueous solution is described. Cephalosporin derivatives (cephalothin sodium, cephacetrile sodium, cefamandole lithium and nafate, cefoperazone sodium and ceftizo... | 18,964,102 |
[Not Available]. | Knowing the values of the equilibrium constants corresponding to the reactions N(2)O(4) right harpoon over left harpoon 2NO(2) and N(2)O(4) right harpoon over left harpoon NO(+) + NO(3)(-) in sulpholane, we have undertaken the electrochemical study of N(2)O(4) by means of linear and cyclic voltammetry at the platinum e... | 18,964,108 |
Adsorption of metal ions on activated carbon from aqueous solutions at pH 1-13. | Adsorption of microgram amounts of 20 metal species on activated carbon powder from aqueous solutions of pH 1-13 was investigated. The species examined were Cs(I), Y(III), Ce(III), Ti(IV), Zr(IV), Cr(III), Cr(VI), Mn(II), Fe(III), Co(II), Ni(II), Ru(III), Cu(II), Ag(I), Zn(II), Cd(II), Al(III), Pb(II), Sb(III) and Bi(I... | 18,964,109 |
Behaviour of some dialkyl- and trialkyl-lead compounds in the hydride-generation procedure using a non-dispersive atomic-fluorescence detector. | The method of generating covalent hydrides by reduction with sodium tetrahydroborate was applied to aqueous solutions containing traces of R(3)Pb(+) and R(2)Pb(2+) compounds (R = methyl, ethyl). For each compound the effects of sample acidity, sodium tetrahydroborate and hydrogen peroxide concentrations, reaction-vesse... | 18,964,111 |
Multiparametric curve fitting-IX Simultaneous regression estimation of stoichiometry and stability constants of complexes. | A chemical model (i.e., the number of complexes, their stoichiometry and stability constants with molar absorptivities) in solution equilibria may be established by (i) the trial-and-error method in which stability constants are estimated for an assumed set of complexes in the mixture and a fitness test is used to reso... | 18,964,117 |
A new reagent for determining trace selenium by gas chromatography: 1,4-dibromo-2,3-diaminonaphthalene. | 1,4-Dibromo-2,3-diaminonaphthalene is proposed as a reagent for conversion of selenium into a piazselenol, for determination by gas chromatography. The limit of detection is 0.03 ng of selenium. | 18,964,118 |
Solvent extraction of zinc with 5,7-dichloro-2-methyl-8-hydroxyquinoline into chloroform. | The distribution equilibria of the zinc complex with 5,7-dichloro-2-methyl-8-hydroxyquinoline in the water-chloroform system have been studied at 25 degrees . The influence of pH, reagent and metal concentrations, and the presence of sodium perchlorate in the aqueous phase has been determined. From quantitative evaluat... | 18,964,125 |
The influence of thiourea on the cation-exchange behaviour of various elements in dilute nitric and hydrochloric acids. | Cation-exchange distribution coefficients for 21 elements between the cation-exchange resin AG50W-X4 and dilute nitric and hydrochloric acid containing up to 2.0M concentration of thiourea are presented. The ion-exchange behaviour of the elements and some possible separations are discussed. Four multi-element elution c... | 18,964,128 |
Fluorimetric determination of boron at microgram level. | The synthesis, characterization and application of 2-(2-hydroxybenzylidenimine)benzene-arsonic acid (HBBA) as a reagent for the fluorimetric determination of boron are described. This reagent reacts with boric acid in 85% w/w sulphuric acid medium to yield a fluorescent compound. The reagent is not fluorescent in those... | 18,964,136 |
Extraction and spectrophotometric determination of titanium(IV) with alizarin and fluoride. | The characteristics of the mixed-ligand titanium(IV)-fluoride-alizarin complex, including the optimum conditions of formation and extraction into methyl isobutyl ketone, are described. A simple and sensitive procedure for spectrophotometric determination of titanium has been developed. At pH 9.5-10.3 titanium reacts wi... | 18,964,146 |
Fluorometric determination of nitrite. | A sensitive, simple and rapid fluorometric procedure for the determination of nitrite is described. It is based on the reaction of nitrite with 2,3-diaminonaphthalene in acidic solution to form 1-[H]-naphthotriazole, a highly fluorescent compound in alkaline medium. The detection limit is approximately 0.5 ng ml in the... | 18,964,160 |
Effect of temperature on the determination of aromatic nitro-compounds by coulometrically generated chromium(II). | The analytical utility of the reaction between aromatic nitro-compounds and electrogenerated chromium(II) can be extended to several previously undeterminable compounds by increasing the temperature of the reaction solution. For some substances the stoichiometry of the reduction is changed; for others the rate of react... | 18,964,192 |
Trace zinc determination by synchronous derivative fluorimetry. | A sensitive and selective synchronous-scanning derivative spectrofluorimetric determination of zinc based on the formation of a fluorescent chelate with 2-furaldehyde 2-pyridylhydrazone (FAPH) is described, and its analytical performance compared with that of the ordinary fluorimetric method. The detection limits lie i... | 18,964,201 |
Electroanalytical determination of vinca alkaloids used in cancer chemotherapy. | A differential pulse polarographic method has been developed for determination of the antineoplastic agents vincristine and vinblastine at ng ml level, in biological fluids such as plasma and urine. The vincristine and vinblastine are extracted from urine with Amberlite XAD-2. Linear calibration plots are obtained for ... | 18,964,202 |
Determination of trace amounts of the flotation collectors ethyl xanthate and diethyl dithiophosphate in aqueous solutions by cathodic stripping voltammetry. | A cathodic stripping method has been devised for determination of low concentrations of the flotation collectors ethyl xanthate, diethyl dixanthogen and diethyl dithiophosphate. The limit of detection for ethyl xanthate was 1 x 10(-8)M by the differential pulse technique and with deposition for 2 min at -0.1 V. Three p... | 18,964,204 |
Determination of traces of EDTA, EGTA and DCTA by adsorptive accumulation of their complexes with hg(ii) followed by cathodic stripping. | The strong adsorption of the Hg(II) complexes of EDTA, DCTA and EGTA on a hanging mercury-drop electrode has been utilized in two procedures for cathodic-stripping determination of these complexing agents in water. The first procedure allows the determination of the free ligands or the total amount of 'available' metal... | 18,964,207 |
Spectrometric analysis of non-metals introduced from a graphite furnace into a microwave-induced plasma. | A low-power helium microwave-induced plasma, sustained in a cylindrical TM(010) cavity, has been used with sample introduction from a graphite furnace. An end-on optical configuration was employed to monitor both atomic and ionic emission from Cl, I, S and P. The operating parameters were optimized with respect to the ... | 18,964,219 |
Studies on fluorescein-III The acid strengths of fluorescein as shown by potentiometric titration. | Potentiometric back-titration of yellow solid fluorescein (H(2)Fl) and of red solid fluorescein in alkali with acid yielded titration curves that were practically identical in shape and position. The end-points at pH 8.5, 5.40 and 3.3 corresponded, respectively, to titration of the excess of standard alkali, and the su... | 18,964,223 |
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