title stringlengths 0 1.13k | abstract stringlengths 1 15.7k | PMID int64 22 36.5M |
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Identification of an organic compound leached from a membrane filter. | An organic compound leached from a Millipore HA filter has been identified as the non-ionic surfactant polyoxyethylene nonylphenyl ether with a degree of polymerization of 4-10 for the ethylene oxide unit. It is suggested that the Millipore HA filter should be used only after several rinses with sample or doubly-distilled water. | 18,962,149 |
Contributions to the basic problems of complexometry-XXVII. Influence of magnesium on masking of calcium with fluoride in the determination of manganese. | Determination of manganese in the presence of calcium and magnesium after their masking with ammonium fluoride was reinvestigated. Normally such a determination gives low results caused by co-precipitation of manganese with calcium fluoride. It has been found that the co-precipitation is highest when magnesium is absent in the solution. With increasing concentration of magnesium ions co-precipitation of manganese decreases and at the ratio ca:Mg = 0.5-1 is entirely eliminated. An explanation of this phenomenon is discussed. | 18,962,164 |
Determination of acid-soluble and total rhodium on alumina-supported catalysts. | Characterization of alumina-supported catalysts required determination of rhodium by atomic-absorption spectroscopy (AAS). Catalysts were loaded with 0.1-2.0% rhodium chloride and calcined at 400 degrees . Rhodium remaining as the chloride was regarded as the soluble form, while that converted into the oxide or bonded to the alumina was regarded as the bonded form. By selective dissolution procedures, soluble rhodium was leached from the substrate and determined by AAS. Total rhodium was determined after the catalyst had been fused with sodium peroxide. Bonded rhodium can be determined by difference or by analysing leached residue. Optimization of AAS conditions, use of spectroscopic buffer solution and elimination of interelement interferences are discussed. | 18,962,171 |
Extraction and spectrophotometric determination of thallium(III) with thiothenoyltrifluoroacetone. | A procedure is described for the extractive photometric determination of thallium(III) with thiothenoyltrifluoroacetone in carbon tetrachloride. Thallium(III) is extracted quantitatively at pH 4-5 and the bright yellow extract obeys Beer's law over the Tl(III) concentration range 2.5-17.5 mug/ml, at 440 nm. Thallium(III) can be determined in the presence of a large number of cations and anions. | 18,962,181 |
Sensitivity enhancement in flameless atomization systems by use of a rigid tungsten collar. | Sensitivity enhancement was achieved in a flameless atomization system by the insertion of a rigid tungsten "collar" 1 cm long and 0.5 mm thick. With such a collar the electrical and thermal properties of the furnace were essentially those of the original tube, and the existing power pack could be used without modification. A significant improvement in sensitivity was found for the majority of the sixteen elements studied. The system did not appear to suffer from the deformation problems associated with other systems of atomization from metal surfaces. | 18,962,192 |
Quantitative treatment of substituent effects in the polarographic investigations of some potential antineoplastic 2-amino-4-aryl-5-phenylazothiazoles. | Polarographic reduction of 2-amino-4-aryl-5-phenylazothiazoles takes place in a single 2-electron transfer, giving a diffusion-controlled irreversible wave in the pH range 2.0-10.0. Substituents in the 4-position of the thiazole moiety shift the half-wave potential through conjugation of the system. A correlation of E(sol;1 2 ) with the Brown and Hammett substituent constant has also been established. | 18,962,218 |
Assessment of a new method for the differential pulse polarographic determination of silicon in steel. | A procedure is described by which silicon in steel may be determined by differential pulse polarography after removal of iron. Silicomolybdic acid is formed within 20 min by reaction of the silicon with molybdate in the presence of methyl ethyl ketone: subsequent addition of citrate buffer prevents interference from phosphate and excess of molybdate. At the levels present in high-purity iron ( approximately 0.002%) the precision for silicon is better than that usually quoted for the molybdenum blue method. The steel is dissolved by standard procedures but iron must be removed before the silicon is determined. The lower limit imposed by the polarography is about 10(-5)% silicon, but the practical lower limit is probably set by the difficulty of removing the last traces of iron. | 18,962,245 |
[Not Available]. | Acids conjugated to various phenothiazine derivatives are titrated directly with sodium hydroxide, by means of an automatic thermometric titrimeter. The titration curves have sharp breaks, suitable for analytical use, and these are discussed, in the case of promethazine hydrochloride, as functions of various parameters such as pK(a), the solubility of the product and the enthalpy of neutralization (determined in this work). | 18,962,270 |
4-Amino-3-methyl-5-mercapto-1,2,4-triazole as a gravimetric reagent for determination of silver in silver compounds, alloys and complexes. | A simple, convenient and accurate gravimetric method for the determination of silver is presented. 4-Amino-3-methyl-5-mercapto-1,2,4-triazole precipitates silver quantitatively from ammoniacal tartrate medium. The complex is weighed as AgC(3)H(5)N(4)S after drying at 120-30 degrees . Separation of silver from a large number of cations is described. Application of the method for quantitative analysis of alloys and complexes of silver is reported. The average relative error for the range 20-70 mg of silver is +/- 0.25% and the relative standard deviation at the 40-mg level is 0.2%. | 18,962,291 |
Potentiometric determination of the dissociation constants of an asymmetric sorbent containing l-proline, and the stability constants of its Cu(II) complexes. | The dissociation constants of the carboxyl groups (pK(a1) = 2.2, n = 1.8) and amino groups (pK(a2) = 9.5, n(2) = 1.6) of a sorbent prepared by reacting l-proline with a cross-linked chloromethylated styrene polymer have been determined by potentiometric titration. The potentiometrically measured stability constants of the Cu(II) complexes of the resin (logbeta(1) = 6.9 and log beta(2) = 12.4) were found to be close to the values for the Cu(II) complexes of N-benzyl-l-proline. For complexed resins of alpha-amino-acid type the pH-values of decomplexation do not appear to be directly correlated with the stability constants. | 18,962,307 |
Furoin thiosemicarbazone as an analytical reagent for nickel(II), palladium(II) and copper(II). | Furoin thiosemicarbazone (FTS) reacts with Ni(II), Pd(II) and Cu(II) in aqueous medium, giving yellow solutions at pH 9, 6 and 3 respectively. The complexes have absorption maxima at 360 nm for Ni(II) and Pd(II) and 355 nm for Cu(II). At these wavelengths the reagent absorbance is negligible. The molar absorptivities are 1.54 x 10(4) [Ni(FTS)(2)], 1.98 x 10(4) [Pd(FTS)(2)] and 1.45 x 10(4) 1.mole(-1).cm(-1) (CuFTS). Beer's law is valid up to 4, 5 and 3 ppm for Ni, Pd and Cu respectively. The apparent instability constant of the Ni-FTS system is found to be 6.5 x 10(-11), of the Cu-FTS system 7.1 x 10(-7) and of the Pd-FTS system 3 x 10(-12) at the recommended pH values. The effect of various ions is reported. | 18,962,319 |
Gas chromatographic study of volatile oxides and hydroxides of Tc, Re, Ru, Os and Ir-I Investigation by isothermal gas chromatography. | Traces of radioactive elements were produced by the irradiation of uranium foils (93% (235)U) with thermal neutrons, and of gold foils with 600-MeV protons. They were volatilized as oxides and hydroxides by heating at 1500 degrees in an O(2) or O(2)/H(2)O stream and separated by adsorption chromatography on quartz granules. Compounds in the effluent gas were detected with a Ge(Li) detector and the elements identified by gamma-spectrometry. | 18,962,322 |
Analytical applications of a liquid anion-exchanger for the separation of uranium(IV) in malonate solution. | Uranium was quantitatively extracted with 4% Amberlite LA-1 in xylene at pH 2.5-4.0 from 0.001 M malonic acid. It was stripped from the organic phase with 0.01 M sodium hydroxide and determined spectrophotometrically at 530 nm as its complex with 4-(2-pyridylazo) resorcinol. Of various liquid anion-exchangers tested, Amberlite LA-1 was found to be best. Uranium was separated from alkali and alkaline earth metal ions, thallium(I), iron(II), silver, arsenic(III) and tin(IV) by selective extraction, and from zinc, cadmium, nickel, copper(II), cobalt(II), chromium(III), aluminium, iron(III), lead, bismuth, antimony(III) and yttrium by selective stripping. The separation from scandium, zirconium, thorium and vanadium(V) was done by exploiting differences in the stability of chloro-complexes. | 18,962,334 |
[Not Available]. | The determinations are based on potentiometric titration data (volume of reagent, potential). To avoid any systematic error, the acidity constants are refined together with every other significant parameter (initial protolyte concentration, concentration of impurities, electrode chain characteristics ...) with the program MUPROT. Comparison of the multiparametrically adjusted results with those obtained by the usual methods reveals noticeable discrepancies. Particular attention is paid to carbonate as impurity; to take it into account, modified expressions for the titrant volume are established. The current of nitrogen used in the classical methods shifts the liquid-gas equilibrium of carbonic acid; in that case, only the approximate equations are to be considered. Working with a closed system is proposed as a more rigorous procedure. | 18,962,339 |
Spectrophotometric determination of bismuth with diethylenetriaminepenta-acetic acid. | Diethylenetriaminepenta-acetic acid is used for spectrophotometric determination of bismuth (at 270 nm) in 1.6 M perchloric acid. The system obeys Beer's law in the range 1-40 mug/ml. The method has been tested for the determination of bismuth in pure lead and polymetallic ores. | 18,962,348 |
Benzohydroxamic acid as a reductometric titrant determination of manganese in ores and alloys. | Benzohydroxamic acid has been employed as a reductometric titrant for the determination of manganese in various ores and alloys. The determination is based on the fact that benzohydroxamic acid reduces Mn(VII) quantitatively to Mn(II) in 1.5N sulphuric acid. | 18,962,356 |
Spectrophotometric determination of micro amounts of hydrazine and hydroxylamine alone and in the presence of each other. | Hydrazine and hydroxylamine alone or in the presence of each other are determined at concentrations of 1-10 microg/25 ml with a relative precision of 3-0.8% by using iron(III) in the presence of Ferrozine. | 18,962,372 |
[Remarques sur le microdosage du bore et du germanium dans les composes organiques et mineraux]. | A wet destruction in a Kjeldahl flask followed by spectrophotometric measurement with azomethine H as reagent, combustion in oxygen in a Parr bomb, and destruction by heating with sodium peroxide followed by acidimetric titration of the mannitol-boric acid complex have been tested for the microdetermination of boron in organic and inorganic compounds and compared with the Schöniger-flask method, which fails to give good results in the case of inorganic compounds; the wet-combustion method is the most useful. Similar techniques, combined with the acidimetric titration of the mannitol-germanic acid complex, or spectrophotometric measurement using phenylfluorone as a complexing reagent, or gravimetric determination as GeO(2), have been tested for the microdetermination of germanium, but none of them is entirely satisfactory, for reasons of lack of either universality or precision. | 18,962,382 |
Automated continuous-flow determinations of serum proteins by pulse polarography. | A new flow-through cell is described for application of the dropping mercury electrode to the determination of serum proteins in an automated continuous-flow system. By using differential pulse polarography with short controlled drop times, it is possible to run a rapid automated system at sampling rates of up to 120 per hour with approximately +/- 1% precision and less than 3% carry-over. With the Brdicka reagent, hexa-amminecobalt(III) chloride, various serum proteins can be determined in the range 5-50 mug/ml. The method therefore offers a rapid and sensitive automated procedure for determination of serum proteins. | 18,962,388 |
Influence of the solvent medium on formation of Cu(II), Zn(II) and Ni(II) hexacyanocobaltates. | Investigations on precipitation of metal hexacyanocobaltates from mixed solvent media have confirmed the earlier interpretation of the mechanism and provided further insight into it. | 18,962,402 |
Autoprotolysis constants and acid-base properties of propylene glycol mixtures. | The autoprotolysis constants of propylene glycol and its mixtures with water, acetone, propan-2-ol and chloroform have been determined potentiometrically. In the same solvent mixtures the protolysis constants of the phthalic acid-hydrogen phthalate system have been evaluated and indicate that the solvent is more acidic than water, but less acidic than ethylene glycol. | 18,962,406 |
Electrothermal atomic-absorption spectrometry of antimony by use of a molybdenum micro-tube atomizer. | Electrothermal atomization of antimony has been investigated to clarify the atomization characteristics and interferences from diverse elements, for accurate determination of traces of antimony. Thiourea served to lower the atomization temperature of antimony and to improve the sensitivity. Germanium and phosphoric acid were found to have a pronounced effect on atomization of antimony. The interference of various elements was suppressed in the presence of thiourea. A method involving extraction for determining antimony in metallurgical and geological samples is described. | 18,962,417 |
Anion-exchange behaviour and separation of metal ions on deae-cellulose in oxalic acid media. | The anion-exchange behaviour of 30 metal ions on a weakly basic ion-exchanger (DEAE-cellulose) has been investigated in aqueous oxalic acid media over the concentration range 0.0010-0.50 M. There are marked differences in adsorbability between ter- and quadrivalent metal and bivalent metal groups; the system offers good prospects for group separations. The adsorptions are moderate, generally a few orders of magnitude lower than those on Dowex 1 (a strongly basic resin). Procedures for the separations Se(IV)Se(VI); As(III)As(V); multicomponent separations Mn(II)Co(II)Cu(II)Ti(IV)Zr(IV) and Cd(II)Zn(II)Cu(II), are given to demonstrate the versatility of the system. | 18,962,418 |
Spot-test detection of aryl hydrazines, hydrazones, osazones, oximes and aromatic amines. | Arylhydrazines are detected by oxidation with N-bromosuccinimide and coupling with resorcinol to form azo-dyes which are intensely coloured in alkaline media. Hydrazones and osazones are hydrolysed to form the arylhydrazines, which are then tested for 4-Nitro- and 2,4-dinitrophenylhydrazines are tested for by forming their hydrazone with salicylaldehyde and adding alkali to produce a violet colour. The hydroxylamine formed by the hydrolysis of oximes is oxidized by iodine monochloride in the presence of sulphanilic acid; coupling with 8-hydroxyquinoline forms a dye that is red in alkali. Intense colours are immediately produced when primary, secondary and tertiary aromatic amines are mixed with diacetoxyiodobenzene. All the tests are sensitive and appear to be specific. | 18,962,427 |
Comparison of experimental and calculated relative sensitivity coefficients for spark-source mass-spectrometry of metals. | Sensitivity calibration has been performed for the spark-source mass-spectrometric analysis of iron, copper and aluminium matrices, with standard reference materials. The experimental relative sensitivity coefficients, corrected for discrimination effects in the mass spectrometer, are compared with values obtained with various empirical approaches to calculate relative sensitivity coefficients for an r.f. spark. The best correlation found is only of the order of 50%. | 18,962,433 |
Unusual complexing properties of 2-(2'-pyridyl)- and 2-hydrazino-8-hydroxyquinoline. | The ligands 2-(2'-pyridyl)- and 2-hydrazino-8-hydroxyquinoline form terdentate complexes with a 5,5-bicyclic ring system, the stabilities being greater than those of the corresponding 8-hydroxyquinolinates. This study affords a more complete picture of the behaviour of terdentate 2-substituted 8-hydroxyquinolines. Solutions of these ligands and metal ions are complicated by formation of the protonated species MHL(2+), M(HL)(2+)(2) and MLHL(+). The existence of the protonated species is dependent not only on pH and ligand:metal-ion molar ratio but also on the nature of the metal ion itself. | 18,962,435 |
New chromogens of the ferroin type-IX 2-pyridyl and pyrazinylhydrazones of some pyridyl, pyrazinyl and pyridazinyl ketones and of isatin and phenylglyoxal. | Chromogenic properties of 22 new hydrazones, all ferroin-type compounds, have been evaluated with respect to iron(II), copper(I), cobalt(II) and nickel(II). Some show promise as sensitive reagents for the determination of trace amounts of these metal ions. Stoichiometric ratios were determined for the iron(II) chelates and interpreted to distinguish between syn- and anti-isomers. | 18,962,451 |
A method for removal of chloride interference in determination of aluminium by atomic-absorption spectrometry with a graphite furnace. | Methods for removal of the chloride interferences in determination of aluminium by atomic-absorption spectrometry with a graphite furnace have been investigated. Two mechanisms of chloride interference have been established. The first arises from co-ordination of the chloride to aluminium. This interference can be removed by preventing the co-ordination. The other is due to co-existing chloride salts remaining until the atomization step. This interference can be removed by volatilizing the chloride or by converting it and/or aluminium chloride into another substance such as the oxides before the atomization step. The tetra-ammonium salt of EDTA is very suitable as an additive to overcome chloride interference because of its ability to co-ordinate aluminium and other cations, and also its effect when heated. | 18,962,452 |
Titration of some thiazine dyes with TiCl3 at room temperature. | Methylene Blue and some other thiazine dyes are titrated at room temperature visually and potentiometrically in presence of 0.005-0.1N oxalic acid. The effect of oxalic acid on the conditional potentials of the Ti(IV)/Ti(III) couple is presented. | 18,962,457 |
Study on Semi-Glycinecresol Red complexes with bivalent metal ions. | Semi-Glycinecresol Red (SGCR or H(3)SGCR) was purified by means of chromatography on cellulose and by cation-exchange. A potentiometric, spectrophotometric and ESR study on the complex formation equilibria of several bivalent metal ions with SGCR was performed. The acid-base and metal-ligand stoichiometries were determined, and the formation constants, lambda(max) and absorptivities of the visible-region absorption spectra of the corresponding proton and metal complexes were determined. The copper complexes were examined by ESR spectroscopy. Each metal ion was found to form the 1:1 and 1:2 (metal:ligand) complex species, MSGCR(-) and M(SGCR)(4-)(2), in alkaline solution. However, only Cu(II) was found to form the protonated complexes, CuHSGCR and Cu(HSGCR)(2-)(2), in weakly acidic media. SGCR is suitable as an indicator for Cu(II) in a weakly acidic solution and for Cu(II), Zn(II) and Pb(II) in alkaline solution. | 18,962,471 |
Multiparametric curve fitting-IV Computer-assisted estimation of successive dissociation constants and of molar absorptivities from absorbance-pH curves by the DCLET program. | The program DCLET evaluates the dissociation (or protonation) constants and molar absorptivities (HjL) of all light-absorbing species (HjL), (j = 0,..., J) of a polyprotic acid (HjL) by a non linear regression of the function A = f(pH; pK (a), (HjL)), i.e., by multiparametric curve fitting. The three specific subroutines DATADC, UBBEDC, SKRDC described form part of the general program ABLET. The goodness of fit is tested by statistical examination of the residuals. Heuristic or algorithmic strategies of minimization may be used, and experimental or synthetic data may be processed. By examining the effects on the results of varying the density and distribution of points of a synthetic data set, it is possible to improve the planning of experiments, and by introducing parametric weight, to improve the sensitivity of a particular parameter in a model. | 18,962,488 |
Determination of small concentrations of HCl by derivative formation-a problem and how it might be solved. | In the investigation of methods for the determination of chloride three reactions for making derivatives of HCl have been developed. The individual problems which arise for the different methods are discussed. The reactions are reaction of CrO(3) with HCl to give CrO(2)Cl(2), reaction of epoxides with HCl to produce alpha-chloro-alcohols and reaction of C(6)H(5)HgNO(3) with HCl to form C(6)H(5)HgCl. The detection methods used are gamma-spectrometric measurement of (51)Cr-labelled CrO(2)Cl(2), gas-chromatographic determination of alpha-chloro-alcohols with flame-ionization, electron-capture or electrolytic-conductivity detectors and the determination of C(6)H(5)HgCl by AAS. | 18,962,512 |
Correlation between flame geometry and the absorbance of some elements in the presence of organic solvents. | The correlation between the changes in flame geometry and the sensitivity of atomic-absorption determination of silver, copper, iron and lead in the presence of various solvents (water, ethanol, n-propanol, methyl acetate, ethyl acetate and acetone) has been investigated. The flame geometry was studied by the Schlieren technique. Organic solvents, allowing a greater rate of introduction of solution, enable a greater sensitivity to be achieved. However, owing to the expansion of the reaction zone, the increase in sensitivity is not as great as expected from the amount of sample introduced into the flame. | 18,962,525 |
[Not Available]. | The authors describe the identification by infrared microtechniques (multi attenuated total reflexion) of the residues of eleven substituted ureas used as herbicides, after separation by thin-layer chromatography. The limitations of the method and the interferences from extracts of natural waters are discussed. In the most favourable cases the detection limit is 40 ppM (40 mug/l). | 18,962,532 |
Precipitation of uranium from low-level liquid wastes. | A method for the recovery of uranium from low-level liquid wastes is described. Uranium(VI) is reduced to uranium(IV) in sulphuric-phosphoric acid solution with iron(II). The uranium(IV) is precipitated as the double duoride with sodium. The uranium content of the filtrate is in the low ppm range. Possible modifications to the procedure are discussed. | 18,962,538 |
Photometric reagents for alkali metal ions, based on crown-ether complex formation--III. 4'-picrylaminobenzo-15-crown-5 derivatives. | An extraction study of alkali metal cations has been made with crown-ether reagents, 4'-picrylaminobenzo-15-crown-5 derivatives (HL). On dissociation in alkaline medium, the orange HL gives the blood-red anion L(-) and extracts alkali metal ions into chloroform as coloured complexes of composition ML.HL or ML. The ease of extraction decreases in the order, K(+) > Rb(+) > Cs(+) > Na(+) >> Li(+). The extracted complexes are ML.HL for K(+) and Rb(+), and both ML.HL and ML for Na(+). The Li(+) complex is not extracted. The photometric determination of 10-800 ppm of K(+) is possible in the presence of other alkali and alkaline earth metal ions. | 18,962,544 |
An investigation of a flameless atomic-absorption method for determination of aluminium, calcium, iron and magnesium in sewage sludge. | The methods currently used for the determination of aluminium, calcium, iron and magnesium in sewage sludge are time-consuming. A rapid flameless atomic-absorption procedure, utilizing homogenization of diluted samples as the only pretreatment, has been compared with wet and dry analytical methods followed by flame atomic-absorption analysis, in a statistically designed experiment. Low-sensitivity (secondary absorption) lines have been used for the flameless analysis. The flameless atomic-absorption method described is better than all the other methods tested, with the exception of the nitric-perchloric-hydrofluoric acid digestion procedure. The time saved is substantial and the method could be used advantageously for routine analysis. | 18,962,545 |
Dual-wavelength spectrophotometric determination of cadmium with cadion. | Cadmium has been determined by dual-wavelength spectrophotometry with cadion, p-nitrobenzenediazoaminobenzene-p-azobenzene, and a non-ionic surfactant, Triton X-100. Cadion and its cadmium chelate are dissolved in a micellar solution of the surfactant. The absorbance difference at the wavelength of maximum absorption of the cadmium chelate (477 nm) and that of cadion (566 nm) is measured. A combination of triethanolamine, iminodiacetate and citrate is very effective for masking other ions. Cadmium in zinc metal can be determined without prior separation. | 18,962,550 |
Determination of sulphur by electrolytic hydrogenation. | Certain sulphur compounds such as thiosulphuric acid, polythionic acids, thiocyanic acid, thioureas, thioamides and 2-mercapto-acids are readily electrolytically hydrogenated in 1N sulphuric acid to form hydrogen sulphide which is absorbed in potassium hydroxide solution and titrated with o-hydroxymercuribenzoic acid in the presence of dithizone as indicator. The electrolytic cell consists of a lead anode in 5N sulphuric acid, a porous ceramic tube as diaphragm, and a cathode made of soft iron. The first-order rate-constants of hydrogenation and the results of determination of sulphur in some sulphur compounds are presented. The limit of determination is 0.1 ppm. | 18,962,557 |
Polarographic determination of ampicillin in capsules and tablets. | A new polarographic method is used for quantitative analysis of ampicillin dosage forms. The electroactive product is formed by acidic hydrolysis of ampicillin. It gives a well-developed reduction wave with half-wave potential of -0.91 V vs. SCE. The proposed method has good precision. A major advantage is the selectivity, which makes the determination of ampicillin possible without prior separation of the excipient. | 18,962,573 |
Hydroxide complexes of lanthanides--II: samarium(III) in perchlorate medium. | From the precipitation borderline in the pM'-pH diagram, determined experimentally under CO(2)-free conditions, the stability constants of the mononuclear and polynuclear species of samarium hydroxide have been established. The values found are log beta(1) = -7.5, log beta(2) = -15.0, log beta(3) = -22.7, log beta(4, 3) = -19.5 and log K(s0) = 17.5. They refer to fresh precipitates, prepared at room temperature in sodium perchlorate medium with an ionic strength of 1. | 18,962,586 |
[Acidites et complexes des acides (alkyl-et aminoalkyl-) phosphoniques-IV: acides aminoalkylphosphoniques R(1)R(2)N(CH(2))(n)CR(3)R(4)PO(3)H(2)]. | The acids under study differed from one another in length of the carbon chain [N + H(3)(CH(2))(n)PO(3)H(-) for n = 1, 2, 3], substitution on the nitrogen atom [R(1)R(2)N + HCH(2)PO(3)H(-) for R(1) = H; R(2) = Me, Et and R(1) = R(2)= Me, Et] or extent of branching on the carbon atom adjacent to functional groups [N + H(3)CR(3)R(4)PO(3)H(-) for R(3) = H; R(4) = Me, Et, nPr, iPr, nBu and R(3) = R(4) = Me]. Acidity constants and overall stability constants of complexes formed with Ca(II), Mg(II), Co(II), Ni(II), Cu(II), Zn(II) were obtained with the multiparametric refinement programs MUPROT and MUCOMP, applied to potentiometric data, obtained at 25 degrees , in a 0.1M potassium nitrate medium. In the most general case, the existing species are MHA(+), MA, M(OH)A(-), MH(2)A(2), MHA(-)(2) and MA(2-)(2), where A(2-) stands for the fully ionized ligand; preliminary examination of results points out some predominant microscopic forms. | 18,962,590 |
The influence of pH and complex formation on the ASV peaks of Pb, Cu and Cd. | The effects of pH, electrolyte composition and complex formation on the size and position of the ASV peaks of Pb, Cu and Cd have been systematically evaluated, with an instrument equipped with a mercury thin-film electrode and by applying a linear ramp voltage scan. The peak heights change with pH and the magnitude of the pH effect varies with base electrolyte composition. Anions such as chloride and acetate reduce the signal, as does the presence of excess of ligands such as 2,2'-bipyridyl, NTA and EDTA. Formation of stable chelates (e.g., with EDTA) can lead to total loss of signal, but dissociation of labile complexes can be enhanced by reducing the pH and/or increasing the magnitude of the applied deposition potential, thus producing measurable peaks. The peak potentials vary with pH, and in copper systems there are additional shifts in the presence of citrate, 2,2'-bipyridyl and chloride. With the last two, double peaks are formed and these are attributed to the formation of both Cu(I) and Cu(II) oxidation products. The varied response, particularly in the case of copper, which can follow changes in the base electrolyte composition, supports the need for careful control of the chemical environment in quantitative determination, and raises some queries about the feasibility of using direct ASV for speciation purposes. | 18,962,604 |
Investigations on the usefulness of tiron in separation of metal ions on the macroporous anion-exchanger amberlyst A-26. | The possibility of application of a sulpho-derivative of an aromatic organic complexing agent-tiron-for separation of cations on the macroporous anion-exchanger Amberlyst A-26 has been investigated. Comparative results obtained with Amberlite IRA 400 have proved the macroporous exchanger to be the more useful. The dependence of retention on pH obtained has been established by the batch method for: Ag, Ni, Co(II), Mn(II), Zn, Cd, Pb, Cr(III), Fe(III), Ga, Al, In, Bi, Ti(IV), V(V) By taking advantage of selectivity differences, the following mixtures have been separated: AlGa, AlTi(IV), Ti(IV)Ni, NiFe(III), NiFe(III)Ti(IV). | 18,962,605 |
Titration of phosphonic acid derivatives in mixtures. | An analytical procedure is described for the determination of the weak acids phosphonomethyliminodiacetic acid and phosphonomethyliminoacetic acid in their mixtures, and the dissociation constants of phosphonomethyliminoacetic acid are reported. | 18,962,615 |
Electrochemical detectors for flowing liquid systems. | A review of the theory, applications, and advantages and disadvantages of the major types of electrochemical detectors in flowing systems is presented in this report. | 18,962,627 |
Determination of thallium and lead in cadmium salts by anodic stripping voltammetry with addition of surfactants to suppress the cadmium peaks. | Conditions have been found which make possible the determination of thallium and/or lead in cadmium and its salts without preliminary separation. The electrochemical activity of the cadmium, which usually interferes in the determination of thallium, is inhibited by the addition of 0.01% of polyethylene glycol of M.W. 4000. Thallium is determined by electrolysis at -0.74 V vs. SCE, in 0.1M EDTA solution: 10(-1)M thallium can be determined in the presence of 0.1M cadmium, while copper and lead at 10(-2)M and 10(-5)M respectively do not interfere. Lead is determined in 0.1M acetic acid containing 0.1% cetyltrimethylammonium bromide (CTAB). The addition of CTAB shifts the cadmium peak, as well as the optimum deposition potential for cadmium, to more negative values, making it possible to determine lead in the presence of cadmium as long as the deposition potential lies in the range between -0.50 and -0.56 V vs. SCE. Lead can be determined in the presence of ten times as much thallium. | 18,962,633 |
Using orthogonal array to obtain gradient liquid chromatography conditions of enhanced peak intensity to determine geniposide and genipin with electrospray tandem mass spectrometry. | The conditions to determine geniposide and genipin using gradient liquid chromatography-tandem mass spectrometry (LC-MS/MS) via electrospray ionization were obtained using fractional factorial experimental design approaches, guided with Taguchi orthogonal arrays to enhance peak intensity. Geniposide, the major iridoid glycoside component of Gardenia herbs, which has been recognized to have choleretic effects, is transformed to genipin in animals. In this paper, the gradient establishment times, ionization source temperatures, and the concentrations of volatile additive ammonium acetate were investigated under the guidance of experimental designs to obtain LC-MS/MS signals of the highest peak intensity. Using geniposide and genipin standards, the methods are validated at the concentration ranges of 0.5-1000ng/mL and 10-5000ng/mL using ammonium adducts. The correlation coefficients of geniposide and genipin standard curves are greater than 0.999. Compared with the sensitivities of previously published LC-MS/MS methods, the methods developed in this work provide 6-fold sensitivity improvement. The lowest concentrations of geniposide and genipin, 0.19 and 2ng/mL, respectively, to generate detectable LC-MS/MS signal peaks are one order of magnitude lower than the repoered values in previous publications. The measurement accuracy and precision of geniposide are within 23% and 15%, respectively. The accuracy and precision of genipin are within 16% and 12.5%, respectively. When the validated calibration curves of geniposide and genipin are used to determine spiked control samples in rat blood dialysates, the geniposide determination errors are within 15% accuracy and within 5.8% precision, respectively, and the genipin determination errors are within 23% accuracy and within 3.6% precision, respectively. | 18,962,644 |
Determination of decamethylcyclopentasiloxane in river water and final effluent by headspace gas chromatography/mass spectrometry. | A method is described for the analysis of decamethylcyclopentasiloxane (D(5)) in river water and treated waste water using headspace gas chromatography/mass spectrometry. Internal standard addition to samples and field blanks was carried out in the field to provide both a measure of recovery and to prevent any exposure of samples to laboratory air, which contained background levels of D(5). Measured levels of D(5) were typically in the range <10-29ngL(-1) in the River Great Ouse (UK) with slightly higher levels in the River Nene (UK). The measured concentration of D(5) in treated waste water varied between 31 and 400ngL(-1), depending on the type of treatment process employed. | 18,962,646 |
Conventional and narrow bore short capillary columns with cyclodextrin derivatives as chiral selectors to speed-up enantioselective gas chromatography and enantioselective gas chromatography-mass spectrometry analyses. | The analysis of complex real-world samples of vegetable origin requires rapid and accurate routine methods, enabling laboratories to increase sample throughput and productivity while reducing analysis costs. This study examines shortening enantioselective-GC (ES-GC) analysis time following the approaches used in fast GC. ES-GC separations are due to a weak enantiomer-CD host-guest interaction and the separation is thermodynamically driven and strongly influenced by temperature. As a consequence, fast temperature rates can interfere with enantiomeric discrimination; thus the use of short and/or narrow bore columns is a possible approach to speeding-up ES-GC analyses. The performance of ES-GC with a conventional inner diameter (I.D.) column (25 m length x 0.25 mm I.D., 0.15 microm and 0.25 microm d(f)) coated with 30% of 2,3-di-O-ethyl-6-O-tert-butyldimethylsilyl-beta-cyclodextrin in PS-086 is compared to those of conventional I.D. short column (5m length x 0.25 mm I.D., 0.15 microm d(f)) and of different length narrow bore columns (1, 2, 5 and 10 m long x 0.10 mm I.D., 0.10 microm d(f)) in analysing racemate standards of pesticides and in the flavour and fragrance field and real-world-samples. Short conventional I.D. columns gave shorter analysis time and comparable or lower resolutions with the racemate standards, depending mainly on analyte volatility. Narrow-bore columns were tested under different analysis conditions; they provided shorter analysis time and resolutions comparable to those of conventional I.D. ES columns. The narrow-bore columns offering the most effective compromise between separation efficiency and analysis time are the 5 and 2m columns; in combination with mass spectrometry as detector, applied to lavender and bergamot essential oil analyses, these reduced analysis time by a factor of at least three while separation of chiral markers remained unaltered. | 18,962,648 |
Water analysis by spark-source mass-spectrometry after preconcentration on activated carbon. | For trace analyses of environmental waters, spark-source mass-spectrometry has been combined with a preconcentration procedure involving chelation of the dissolved trace elements with oxine and subsequent adsorption of the oxinates and naturally occurring organic and colloidal metal species onto activated carbon. The activated carbon is filtered off and ashed at low temperature. The residue is dissolved, an internal standard and pure graphite are added and, after drying, the electrodes are prepared. The photographically recorded mass spectrum is evaluated by a suitable computer routine. The error of the procedure is around 30%. While this preconcentration and analysis procedure is capable of measuring about 40 elements quantitatively, in practice 10-25 trace elements are determined simultaneously above the 0.1-mug/l. detection limit, as is illustrated by analyses of drinking water, surface and ground water samples. Although a sophisticated technique, SSMS can be considered for regular panoramic survey analyses. | 18,962,695 |
[Not Available]. | The proton concentration resulting from the dissociation of a moderately strong dibasic acid can be precisely determined by means of an acid-base indicator by differential spectrophotometry. The dissociation constants are then calculated by linear regression of the appropriate function. The method was tested on the first two dissociation constants of protonated O-phosphoserine in aqueous solution (25 degrees , KNO(3) 0.1M): the values found are pK(1) = 0.72 (3sigma = 0.08) and pK(2) = 2.14(6) (3sigma = 0.01). | 18,962,700 |
Silver-reductor method for determination of iron in iron ores and iron-ore sinters. | A new technique for the quick dissolution of iron ore, magnetite and sinter products has been developed. The sample is dissolved with thioglycollic acid and hydrochloric acid, the excess of thioglycollic acid is oxidized, and the iron is reduced in the silver reductor. | 18,962,704 |
Construction of a liquid-membrane type periodate ion-selective electrode and its application to the potentiometric titration of alpha-diols and alpha-amino-alcohols. | The construction of a liquid-membrane type periodate ion-selective electrode and its application to the potentiometric titration of alpha-diols and alpha-amino-alcohols are described. The ion-pair of periodate anion with Capriquat (tri-n-octylmethylammonium chloride), is easily extracted into nitrobenzene, and this extract is employed as a liquid ion-exchange membrane. The calibration curve shows Nernstian response towards periodate ion over the concentration range from 10(-1)M to 10(-7)M with a slope of 60 mV/pIO(-)(4). Selectivity coefficients with respect to various ions were evaluated. The electrode potential was independent of pH in the range 2.5-7.5. Some alpha-diols and monoethanolamine were successfully titrated potentiometrically with the aid of the present electrode. | 18,962,713 |
A new spectrophotometric method for differentiating mononuclear and polynuclear complexes and for determining their extraction constants. | A new spectrophotometric method is proposed for differentiating mononuclear and polynuclear complexes as well as for determining the extraction constant K*(e) of any complex A(m)B(n). The method is based on the effect of dilution on the degree of dissociation of the complex. The precision of log K*(e) is +/- 0.03 when the degree of extraction of the metal is between 20 and 60%. The highest values of log K*(e) determinable by this method are 7, 19, 12 and 18 for 1:1, 2:2, 2:1 and 3:1 complexes, respectively. | 18,962,723 |
Age at onset influences on wide-ranged clinical features of sporadic amyotrophic lateral sclerosis. | To profile the detailed clinical features of sporadic amyotrophic lateral sclerosis (ALS) on large-scale samples in Japan. We assessed the clinical features of sporadic ALS patients in Japan, based on the nationwide registration system of the Ministry of Health, Labor and Welfare of Japan. We described 3,428 new cases registered cases between 2003 and 2006 to analyze initial symptoms and related clinical features, 4,202 cases registered in the single year of 2005 to describe the cross-sectional overview of the ALS patients, and a total of 2,128 cases with tracheostomy positive pressure ventilation (TPPV) from all of the registration data from 2003 to 2006 to describe the features of ALS patients with TPPV. The patients with an older age at onset progressed more rapidly to the TPPV stage than those with a younger age at onset. The subpopulation of patients with long-standing TPPV showed ophthalmoplegia, while its appearance rate was less in the patients with an older age at onset than in those with a younger age at onset. Furthermore, age at onset strongly influenced the frequency of initial symptoms: dysarthria, dysphagia, neck weakness and respiratory disturbance were more frequent in patients with an older age at onset, while upper or lower limb weakness was observed more frequently in patients with a younger age at onset. In addition, those initial symptoms were still the most prominent at the follow-up stage, suggesting that the initial symptoms determine the major clinical features even in advanced illness. Our present study demonstrated that symptomatic features of ALS are strongly influenced by the age at onset by the large scale of samples. | 18,962,725 |
Statistical adjustment of parameters for potentiometric titration data. | The paper deals with the statistical problem of adjusting parameters to the experimental data from potentiometric titrations. The parameters to be refined are, first, the value of the stability constant of the titration reaction, and, second, the equivalence volume. The paper discusses the selection of the error variable and the need for weighting in the optimization procedure. The case where both parameters are refined at the same time is also considered. Special reference is made to linearized titration curves for the determination of the equivalence volume. | 18,962,730 |
Determination of lanthanides with m-toluidinyloxamic acid. | m-Toluidinyloxamic acid is shown to be about as efficient as the para isomer as a gravimetric reagent for La, Pr and Nd. Conditions have been established for the determination of these lanthanides in presence of a number of metal ions. | 18,962,734 |
Estimation of individual thio-salts and sulphate in flotation mill solutions. | This paper presents methods found to be suitable for the determination of thio-salts and sulphate in flotation mill solutions. Thiosulphate, tetrathionate and trithionate are estimated spectrophotometrically after cyanolysis. A modified iodimetric procedure is used for sulphite and a titrimetric method for direct determination of sulphate. The observation that dithionate is not oxidized by hydrogen peroxide but is oxidized to sulphate by potassium chlorate-nitric acid mixture is the basis for estimation of dithionate. | 18,962,735 |
Derivatives of 2-thiohydantoin as spectrophotometric analytical reagents-II Condensation at C-5 with aromatic non-pyridine aldehydes. | The synthesis, characteristics, properties and reactions with metallic ions of six aromatic derivatives of 2-thiohydantoin have been studied. The reagents exhibit two pK values in aqueous solution, and with Pd(II), Au(III), Ag(I) and Hg(I) and (II), especially with the first, form stable complexes with molar absorptivities adequate for spectrophotometric measurements. | 18,962,740 |
Amperometric determination of 2-benzothiazole sulphenamide accelerators. | A simple method for the amperometric estimation of N-cyclohexyl-2-benzothiazole sulphenamide, N-dicyclohexyl-2-benzothiazole sulphenamide, 2-(morpholinothio)benzothiazole and N-tert.-butyl-2-benzothiazole sulphenamide is reported. The results are obtained within 5 min and are correct within +/- 2.0%. | 18,962,755 |
Ion-exchanger colorimetry-VI Microdetermination of nickel in natural water. | Ion-exchanger colorimetry with 1-(2-pyridylazo)2-naphthol (PAN) has been developed for the determination of nickel at the mug/l. level in natural water. With 1 litre of sample the detection limits are 1.3 x 10(-9)Mi.e., 0.077 mug/l. for fresh water and 5.8 x 10(-9)Mi.e., 0.34 mug/l. for sea-water. The distribution ratio is 5 x 10(4). Copper and zinc, which form coloured species with PAN in the resin phase, can be completely eluted with a masking solution composed of EDTA and thioglycollic acid (pH 7.8). Cobalt can be determined simultaneously by measurement at 628 nm. | 18,962,762 |
Properties of cis- and trans-bis(crown ether)s for complexation and extraction of alkali metal picrates. | The properties of cis- and trans-bis(crown ether)s containing benzo-15-crown-5 or benzo-18-crown-6 units as complexants and extractants for alkali metal picrates have been studied. The optical spectra suggest that the cis-bis(crown ether)s can form intramolecular 2:1 crown ether unit/cation complexes with particular metal cations easily, while the trans-bis(crown ether)s can form only 1:1 crown ether unit/cation complexes because of the unfavourable trans configuration for the formation of the 2:1 complexes. It was found that the cis isomer possesses much higher extractive power than the trans isomer for the metal cations, which also reflects their complexing properties. The extraction equilibrium constants and thermodynamic quantities have been also evaluated, and the effect of the stereochemical structure of the bis(crown ether) on the complexing and extractive properties is discussed. | 18,962,783 |
Standardization of EDTA by spectrophotometric titration, with metallic copper as standard. | The standardization of EDTA against electrolytically pure copper is described. The copper is dissolved and titrated spectrophotometrically with EDTA at pH 5.0 without an indicator. A relative standard deviation of 0.009% was achieved. | 18,962,786 |
Photometric determination of copper with N-(dithiocarboxy)sarcosine after preconcentration with amberlite xad-2 resin. | The copper(II) chelate of N-(dithiocarboxy)sarcosine (DTCS) is sorbed on a column of Amberlite XAD-2 resin from a pH-7 phosphate solution (0.1M) and stripped with a pH-9.0 ammonia solution (0.2M) in 60% methanol. The absorbance of the eluted chelate is measured at 432 nm against water. Sodium nitrilotriacetate, sodium tripolyphosphate, and EDTA can be used to mask interfering metal ions other than mercury(II), the resulting complexes not being sorbed on the resin. The mercury(II) chelate of DTCS is also sorbed on and stripped from the column along with the copper chelate, but does not interfere in the photometric determination of copper, because it is colourless. The recovery of copper(II) is quantitative from test solutions (50-500 ml) of any salinity up to that of sea-water. Concentration factors of up to about 20 are obtained. The method is highly selective for copper and can be applied to its determination in sea-water. | 18,962,798 |
The determination of oxygen in powdered tungsten carbide by reducing fusion: Suppression of primary carbon dioxide, selection of working conditions and adsorbed-moisture effects. | A method for the reducing fusion determination of oxygen in powdered tungsten carbide is described. It is shown that, as theory predicts, tungsten carbide may evolve its oxygen content not only as carbon monoxide but also as perceptible quantities of carbon dioxide. An easy suppression of this primary carbon dioxide, and thus of any error associated with it made when computing the sample oxygen content, is obtained by the simple expedient of dropping the samples into the crucible a few seconds after having started the instrument analytical cycle, i.e. when the crucible is already at very high temperature. Criteria followed in the selection of the sample fusion conditions and their possible application to the analysis of massive tungsten carbide samples are discussed. The very large effect of the adsorbed moisture content on the results is made evident, and practical means (preliminary water desorption from samples kept at 200 degrees under high vacuum) to overcome it are suggested. | 18,962,814 |
Laboratory microcomputer system for the development of microcomputer-controlled analytical instrumentation. | Researchers in analytical procedures can acquire greater control over their experimental parameters, procedures and the mathematical operations used to manipulate and evaluate their data, by incorporating microcomputer technology into their laboratory instrumentation. A hybrid microcomputer system has been assembled to aid in the development of microcomputer-controlled analytical instrumentation and to enhance performance of microcomputer-controlled instrumentation through improved logic sequencing. Fundamental hardware modules, including the central processing, memory and input/output are specified. These modules are described in terms of the hardware system features necessary for effective programming capabilities. Included are those dealing with burning of programs on erasable programmable read only memory and with the types and sizes of memories required. Software elements are described in terms of system programming features required for creating and incorporating the desired logic sequencing into analytical instrumentation. Although language selection and installation are not examined in complete detail, some problems encountered in this area are discussed. | 18,962,831 |
Coulometrically generated copper(II) in acetonitrile as an analytical oxidant. | Copper(II) was generated at 100% current efficiency from solutions of copper(I) perchlorate in acetonitrile. Micromole quantities of ferrocene and several alkyl-substituted ferrocenes were determined with high precision and accuracy. Hydroquinone and several thiols, on the other hand, could not be determined because of the lack of an acceptor for the protons produced upon oxidation. | 18,962,837 |
Mixed-ligand complexes of iron and hydroxy-1,10-phenanthrolines. | The half-wave potentials of all of the possible tris-complexes formed between iron(II) and 1,10-phenanthroline (A), 4-hydroxy-1,10-phenanthroline (B), and 4,7-dihydroxy-1,10-phenanthroline (C) have been measured at a rotated platinum electrode. Values on the hydrogen scale are 1.06 V for A(3)Fe(II), 0.78 for A(2)B, 0.58 for A(2)C, 0.60 for AB(2), 0.39 for B(3), 0.39 for ABC, 0.21 for AC(2), 0.22 for B(2)C, 0.06 for BC(2), and -0.10 for C(3) at pH 11.0, 25 degrees , and ionic strength 0.2. Half-wave potentials of the parent binary complexes are constant from pH 9 to 13 and are equal to the conditional reduction potentials. The mixed complexes are stable from pH 10 to 12, and form a redox indicator system with a continuous range of accessible potentials from -0.10 to +1.06 V vs. NHE. | 18,962,841 |
Liquid-liquid extraction of osmium thiocyanate with hexamethylphosphoramide and direct spectrophotometric determination in the organic phase. | The use of hexamethylphosphoramide (HMPA) in the osmium-thiocyanate system makes the method more sensitive and selective. The blue colour formed by osmium(VIII) with thiocyanate in 1.5M hydrochloric acid is intensified in the presence of HMPA and the complex becomes readily extractable into chloroform. The colour system has its absorption maximum at 595 nm and obeys Beer's law over the range 0.5-16 mug of Os per ml. The optimum range is 2-10 mug/ml. The molar absorptivity is 2.09 x 10(4)l.mole(-1).cm(-1). The method is simple, sensitive and free from interference from many metal ions, including ruthenium and other platinum metals. | 18,962,858 |
Effect of cumulus cell coculture and oxygen tension on the in vitro developmental competence of bovine zygotes cultured singly. | The customary practice in bovine in vitro embryo production (IVP) is to handle oocytes and embryos in groups; although there are several reasons for establishing an IVP system for individual embryos that allows for following a single oocyte from retrieval through development to the blastocyst stage. To date, reports of individual IVP are inconsistent, and in most cases, resulted in unsatisfactory blastocyst rates. The objective of this study was to develop an efficient system for routine in vitro culture of individual bovine embryos. Single culture of zygotes in 2 different culture volumes (20 and 500microL) yielded less than 3% blastocysts in experiment 1. In an attempt to improve these results, cumulus cells were added to the culture medium in experiment 2, after which blastocyst rates increased from 2.9 to 21.8% (P<0.05). The third experiment revealed that an atmospheric oxygen tension, which is commonly used with somatic cell coculture, was not beneficial during individual embryo-cumulus cell coculture, because it resulted in lower blastocyst rates (Odds ratio 0.57, P<0.001) and in lower blastocyst cell numbers (P<0.05), when compared to culture in 5% oxygen. Grouped vs. single culture and reduced oxygen tension did not have a significant effect on cleavage and hatching rates. In experiment 4, three different cumulus cell coculture conditions during individual culture were tested and compared with the cleavage, blastocyst and hatching rates, and cell number of group culture (73.2%, 36.4%, 66.7% and, 155.1+/-7.26, respectively). The outcome variables after individual embryo culture on a 5-day-old cumulus cell monolayer (74.1%, 38.2%, 71.9% and 133.4+/-9.16, respectively), and single culture in the presence of added cumulus cells (69.9%, 31.9%, 66.7% and 137.3+/-8.01, respectively) were not significantly different from those obtained after group culture (P<0.05). Though, individual culture in a cumulus cell conditioned medium significantly reduced both the cleavage (59.0%) and blastocyst rates (6.3%). These results demonstrate that single culture of bovine zygotes can be fully sustained by coculture with cumulus cells in a low oxygen environment; implementation of these findings in our IVP system produced blastocysts comparable in quantity and quality to those obtained by group culture. These results were consistently achieved after acquiring experience and expertise in the handling of single zygotes. | 18,962,875 |
Room-temperature phosphorescence and fluorescence of nitrogen heterocyclics adsorbed on silica gel chromatoplates. | The room-temperature phosphorescence of benzof]quinoline and phenanthridine has been enhanced considerably by spotting HBr-ethanol solutions of the compounds onto silica gel chromatoplates. Acridine showed no room-temperature phosphorescence but gave very strong fluorescence on silica gel chromatoplates. The analytical aspects are discussed, and some evidence is provided for the interactions of the compounds with the substrate. | 18,962,881 |
Aquametric submicro determination of water content of biopolymer preparations and its application in deriving hydration isotherms. | A rapid aquametric submicro method is proposed for determining 10-100,mug of bound water in 20-60 mug amounts of biopolymers. This method has been applied in deriving isotherms of water-vapour adsorption by biopolymer preparations (proteins, tRNA), in a dynamic mode requiring only 5 mg of the substance. The BET equation was used to determine the effective capacity (h) of a monolayer in the course of sorption (h --> ) and desorption (h <-- ), corresponding to accessible primary hydration sites on the biopolymer molecule surface. As has been established for proteins with known spatial structure, omega-amide groups of Asn and Gln residues and ion-pair forming groups do not participate in the formation of the BET-monolayer during sorption. Such an interpretation of the isotherms underlies the estimation of the number of surface and screened polar groups in the molecules of biopolymers with a spatial structure not yet established from amino-acid analysis and hydration isotherms. The maximum hydration (H(s)) of globular proteins is much less pronounced than that of tRNA, which can be explained by an irregular arrangement of sterically separated primary hydration sites which do not form a matrix for distribution and ordering of water at great distances. The deficiency of sorption sites because of sterically inaccessible groups is a trait common to biopolymers in general. Therefore, hydration isotherms may characterize certain aspects of the macromolecular structure, such as compactness, degree of screening of the polar groups, regularity of arrangement of the primary hydration sites, and so on. | 18,962,884 |
Short leucine-rich glycoproteins of the extracellular matrix display diverse patterns of complement interaction and activation. | The extracellular matrix consists of structural macromolecules and other proteins with regulatory functions. An important family of the latter class of molecules found in most tissues is the small leucine-rich repeat proteins (SLRPs). We have previously shown that the SLRP fibromodulin binds directly to C1q and activates the classical pathway of complement. In the present study we further examine the interactions between SLRPs and complement. Osteoadherin, like fibromodulin, binds C1q and activates the classical pathway strongly while moderate activation is seen in the terminal pathway. This can be explained by the interaction of fibromodulin and osteoadherin with factor H, a major soluble inhibitor of complement. Also, chondroadherin was found to bind C1q and activate complement, albeit to a lesser extent. Chondroadherin also binds factor H. We confirm published data showing that biglycan and decorin bind C1q but do not activate complement. In this study a similar pattern is seen for lumican although its affinity for C1q is lower than for biglycan and decorin. Furthermore, using electron microscopy and radiolabeled SLRPs, we demonstrate two different classes of SLRP binding sites on C1q, to head and stalk respectively, where only binding to the head appears to be activating. We propose a role for SLRPs in the regulation of complement activation in diseases involving the extracellular matrix, particularly those characterized by chronic inflammation such as rheumatoid arthritis, atherosclerosis, osteoarthritis and chronic obstructive lung disease. | 18,962,898 |
Structural features of T cell receptor variable regions that enhance domain stability and enable expression as single-chain ValphaVbeta fragments. | The variable (V) domains of antibodies and T cell receptors (TCRs) share sequence homology and striking structural similarity. Single-chain antibody V domain constructs (scFv) are routinely expressed in a variety of heterologous systems, both for production of soluble protein as well as for in vitro engineering. In contrast, single-chain T cell receptor V domain constructs (scTCR) are prone to aggregation and misfolding and are refractory to display on phage or yeast in their wild-type form. However, through random mutagenesis and yeast display engineering, it has been possible to isolate scTCR mutants that are properly folded and displayed on the yeast surface. These displayed mutants can serve not only as a scaffold for further engineering but also as scTCR variants that exhibit favorable biophysical properties in Escherichia coli expression. Thus, a more comprehensive understanding of the V domain mutations that allowed display would be beneficial. Our goal here was to identify generalizable patterns of important mutations that can be applied to different TCRs. We compared five different scTCRs, four from mice and one from a human, for yeast surface display. Analysis of a collection of mutants revealed four distinct regions of TCR V domains that were most important for enabling surface expression: the Valpha-Vbeta interface, the HV4 of Vbeta, and the region of the Valpha and Vbeta domains normally apposed against the constant (C) domains. Consistent with the role of the V-C interface in surface display, reconstitution of this interface, by including the constant domains of each chain, allowed V domain display and alphabeta chain association on the yeast surface, thus providing an alternative TCR scaffold. However, the surface levels of TCR achieved with engineered scTCR mutants were superior to that of the ValphaCalpha/VbetaCbeta constructs. Therefore, we describe further optimization of the current strategy for surface display of the single-chain format in order to facilitate yeast display engineering of a broader range of scTCRs. | 18,962,897 |
Fundamental investigation of thermal properties of rare-earth beta-diketonates. | The thermal properties of the rare-earth chelates of Htfa (trifluoroacetylacetone) and Hhfa (hexafluoroacetylacetone) have been investigated. Thermogravimetric curves were obtained by heating samples in the injection chamber of a gas chromatograph, both in an atmosphere of helium, and of helium containing ligand vapour. None of the chelates was completely vaporized in a helium atmosphere at temperatures up to about 240 degrees , but the tfa chelate of Lu and all the hfa chelates were completely vaporized in the atmosphere of helium containing ligand vapour. The vapour pressures and heats of vaporization of these chelates were also measured. | 18,962,924 |
Hydrodynamic modulation voltammetry. | Highly efficient background-correction techniques applicable to voltammetric methods of trace analysis can be developed by modulating the convection rate of the solution at a solid electrode surface. The theoretical aspects, advantages, disadvantages, and analytical applications of the various batch and flow approaches to hydrodynamic modulation voltammetry are discussed, together with trends in future developments. | 18,962,941 |
Silmization of stainless-steel frits for use in trace metal analysis by high performance liquid chromatography. | A simple method has been developed to minimize the interferences related to the metal parts of an analytical system used for trace metal analysis by HPLC. This is accomplished by blocking the exposed metal surfaces with an organosilane. The effect of the silanized stainless steel frits has been demonstrated by injecting diethyldithiocarbamate into columns with and without high metal surface area components. The coating of the silane is quite stable for routine use. | 18,962,951 |
A simple method for the determination of benzo[a]pyrene and benzo[k]fluoranthene in a mixture. | Atmospheric particulate matter is routinely analysed for the concentration of the carcinogen benzo[a]pyrene (BaP). Benzo[k]fluoranthene (BkF) has identical spectral characteristics and interferes in the fluorimetric estimation. A simple method for the determination of BaP in the presence of BkF is described. Based on quenching of the fluorescence of BaP by the addition of small amounts of nitromethane, the method can be used for accurate estimation for wide concentration ratios of BaP to BkF ranging from 0.1 to 10.0. | 18,962,966 |
Indirect method for determining silicon and phosphorus, and analysis of cuban laterites. | A method has been developed for determining silicon and phosphorus in minerals with high iron content, the method being based on the formation, extraction and stripping of molybdenum heteropoly acids and determination of molybdenum after decomposition of the complexes in the aqueous phase from the stripping. | 18,962,977 |
Some aspects of room-temperature phosphorescence in liquid solutions. | Experimental requirements for room-temperature phosphorescence measurements in liquids (RTPL) are discussed. Phosphorescence quantum yields and triplet lifetimes of some brominated naphthalenes and halogenated biphenyls at 77 K in 2-methyltetrahydrofuran and at room temperature in hexane are reported and compared. Surprisingly the naphthalenes show only little loss in quantum yields in going from 77 K to room temperature. Sensitized phosphorescence is discussed as a means of expanding the analytical potential of RTPL. Results with a model system of benzophenone as a donor (analyte) and 1,4-dibromonaphthalene as an acceptor are presented. | 18,962,992 |
Dual-wavelength spectrophotometric determination of copper in sea-water with alpha,beta,gamma, degrees -tetrakis(1-methylpyridinium-4-yl) porphine. | Copper has been determined by dual-wavelength spectrophotometry with alpha,beta,gamma, degrees -tetrakis(1-methylpyridinium-4-yl) porphine (TMPyP). The difference in absorbance at the Soret band of the copper complex (423 nm) and that of TMPyP (446 nm) was measured. Copper in a coastal sea-water sample was preconcentrated with a Chelex-100 separation in which l-cysteine was used as eluent. This combination could determine copper at the ng/ml and sub-ng/ml level. | 18,963,002 |
Indirect spectrophotometric determination of sulphide with the ternary complex system Ag(I)-phen-BPR. | Trace amounts of sulphide can be determined from its effect on the ternary complex system of Ag(+), Bromopyrogallol Red (BPR), and 1,10-phenanthroline (phen). Sulphide in the range 5-120 ng/ml causes a decrease in absorption, that is a linear function of the concentration. Common metal ions such as Na(+), K(+), Ca(2+), Mg(2+), Al(3+), Mn(2+) and anions such as F(-), Cl(-), NO(-)(3), SO(2-)(4), CO(2-)(3), and PO(3-)(4) at the 4 mug/ml level or more do not interfere, but I(-) or CN(-) must be absent. | 18,963,019 |
Hydrophobic indicators for two-phase titrations and their application to the determination of silver and pentachlorophenol. | The hydrophobic dyes tetrabromophenolphthalein ethyl ester and 2,6-dichlorophenolindo-phenol are proposed as visual indicators for two-phase titrations. The aqueous phase is colourless throughout the titration and these indicators make it possible to detect the end-point of the titration by the colour of one or the other phase. The indicators allow the two-phase titration of the silver(I)-1,10-phenanthroline complex with tetraphenylborate and of pentachlorophenol with tetraphenylphosphonium chloride. | 18,963,021 |
Evidence of competitive mechanisms during oxidation of CS(2)N(-)(3) by permanganate ion in alkaline solution. | The oxidation of the 1,2,3,4-thiatriazole-5-thiolate ion, CS(2)N(-)(3), by permanganate ions in alkaline medium has been investigated over a wide range of oxidant concentrations. With a moderate excess of permanganate ion a 17-electron reaction takes place, yielding sulphate, nitrogen and carbon dioxide. With a high permanganate concentration the pseudohalide undergoes a 26-electron reaction yielding sulphate, carbon dioxide and nitrite as final products. These two different stoichiometries arise from the existence of competitive mechanisms and the ratio C(MnO(-)(4))/C(CS(2)N(-)(3)) will determine the course of the reaction. | 18,963,024 |
Arsenic speciation by ion-exchange separation and graphite-furnace atomic-absorption spectrophotometry. | As(III), As(V), monomethylarsenic acid (MMA) and dimethylarsenic acid (DMA) were determined by graphite-furnace atomic-absorption spectrophotometry after separation of the species by ion-exchange chromatography. The detection limits (ng/ml) were DMA 0.02, MMA 2.0, As(V) 0.4 and total arsenic 4.0. As(III) was determined by difference. This system gave better detection limits and/or shorter analysis times than previously reported systems. | 18,963,033 |
[Not Available]. | The reversibility of the determination reaction is the most frequent cause of deviations from linearity of thermometric titration curves. Because of this, determination of the equivalence point by the tangent method is associated with a systematic error. The authors propose a relationship which connects this error quantitatively with the equilibrium constant. The relation, verified experimentally, is deduced from a mathematical study of the thermograms and could probably be generalized to apply to other linear methods of determination. | 18,963,035 |
Non-aqueous cerimetric determination of phenylhydrazides. | A non-aqueous oxidimetric method is described for the determination of some carboxylic acid phenylhydrazides with ammonium hexanitratocerate(IV) in acetonitrile. The end-points have been detected visually with chemical indicators (diphenylamine, diphenylbenzidine, Methyl Red, Malachite Green, Janus Green, Gentian Violet) and potentiometrically. The compounds are smoothly, rapidly and quantitatively oxidized with a two-electron change per hydrazino group. The method is simple, accurate, reliable and widely applicable. | 18,963,039 |
Auditory steady-state responses to bone conduction stimuli in children with hearing loss. | The auditory steady-state response (ASSR) to air-conduction (AC) stimuli has been widely incorporated into audiological test-batteries for the pediatric population. The current understanding of ASSR to bone conduction (BC) stimuli, however, is more limited, especially in the case of infants and children. There are few reports on ASSR thresholds to BC stimuli in infants and young children, and none for infants or children with hearing loss. The objective of this study was to investigate BC ASSR thresholds in young children with normal hearing and various types and degrees of hearing loss. AC and BC ASSR thresholds are reported for 48 young children (mean age+/-SD=2.8+/-1.9 years; age range=0.25-11.5 years; 23 female). Hearing status was classified by assessing all children with a comprehensive test battery including tympanometry, diagnostic distortion-product otoacoustic emissions, click-evoked AC auditory brainstem response, AC and BC ASSR thresholds, and an otologic examination. The subjects were assigned to the categories normal hearing, conductive loss, and sensorineural loss (mild-to-moderate or severe-to-profound), for group analysis. AC and BC ASSR stimuli (carrier frequencies: 0.25-4 kHz; 67-95 Hz modulation rates; 100% amplitude and 10% frequency modulated) were presented using the GSI Audera system. Minimum levels at which spurious BC ASSR occur were established in the group of children with severe-to-profound sensorineural hearing loss (25, 40, 60, 60 and 60 dB for 0.25, 0.5, 1, 2, and 4 kHz, respectively). Children with normal hearing presented mean (1 SD) BC ASSR thresholds of 19 (9), 18 (7), 16 (11), 24 (7), and 26 (8) dB HL at 0.25, 0.5, 1, 2, and 4 kHz, respectively. Significantly lower thresholds (p<0.0001) were obtained for 0.25, 0.5 and 1 kHz than for 2 and 4 kHz. At 0.25 kHz, 39% of thresholds were at the minimum level of spurious response occurrence. More than half (54%) of the BC thresholds in the group with mild-to-moderate sensorineural hearing loss were recorded at or above the minimum levels at which spurious response occurred. In children with conductive hearing loss, the average BC ASSR thresholds corresponded closely to those in the normal hearing group except at 1 kHz and revealed an air-bone gap. Spurious bone conduction ASSR responses limit the intensity range for which the technique may be employed in infants and children, especially at lower frequencies. Consequently, the 0.25 kHz stimulus is not recommended for clinical use. In infants and young children, sensorineural hearing loss of a moderate or greater degree in the high frequencies (1-4 kHz), and of a mild or greater degree in the low frequencies (0.5 kHz), cannot be quantified using BC ASSR. This is due to the presence of the stimulus artifact. In cases of conductive hearing loss, BC ASSR can effectively quantify sensory hearing between 0.5 and 4 kHz, but interpretations must be made cautiously within the limitations of stimulus artifact occurrence across frequencies. | 18,963,045 |
Spectrophotometric study on the reactions of iron(II) and iron(III) with Bromopyrogallol Red and hexadecyltrimethylammonium bromide. | Bromopyrogallol Red (BPR) combines with iron(III) in the presence of hexadecyltrimethylammonium bromide (CTMAB) to form an intensely blue complex having a molar absorptivity of 5.20 x 10(4)l. mole(-1).cm(-1) at 635 nm. The complex contains three molecules of BPR co-ordinated to an iron(III) ion, and two molecules of CTMAB associated with each BPR molecule, giving the overall formula (CTMAB)(6)(BPR)(3)Fe(III). Iron(II) also reacts with BPR and CTMAB in the presence of dissolved oxygen to form the iron(III) complex. No oxidizing or reducing agents are required for the determination of total iron in mixtures of iron(III) and iron(II), and Beer's law is followed from 0.05 to 0.5 ppm iron (1.00-cm cells). Of nine metal ions tested at the 1-ppm level, only manganese(II) and vanadium(V) interfere. Copper(II), cobalt(II), zinc, lead, nickel, aluminium and chromium(III) produce little or no interference when present at 100 ppm concentration. | 18,963,046 |
Addressing, accessing and interfacing peripheral devices to microprocessors. | To utilize the full potential of microprocessors, particularly the small and inexpensive single board systems, for dedicated data acquisition and instrumental system-control functions, it is imperative that researchers have an appreciation of the concepts for addressing, accessing and interfacing peripheral devices to microprocessor systems. These concepts are presented for the Intel 8080, 8085 and Mostek 6502 microprocessors with specific examples for the SDK 80 (8080), SDK 85 (8085) and KIM-1 (6502) single-board microprocessor systems. Features of the control bus architecture are discussed with regard to the movement of data to or from peripheral devices and memory. Utilization of control bus signals and addresses generated from the user program to address and access memory and peripheral devices are discussed and illustrated. The ability of these three microprocessors to handle and service interrupt requests from peripheral devices is discussed. The concepts for interfacing input and output peripheral devices, such as analogue-to-digital and digital-to-analogue converters, to these microprocessors are discussed and illustrated. Software programs suitable for use as subroutines, for input and output of data with these devices are presented and discussed. | 18,963,061 |
Tissue-type plasminogen activator in the ischemic brain: more than a thrombolytic. | Thrombolysis with tissue-type plasminogen activator (tPA) is used for the treatment of patients with acute ischemic stroke. However, a growing body of evidence indicates that, besides the unquestionable benefit from its thrombolytic activity, tPA also has a deleterious effect on the ischemic brain including cytotoxicity and increased permeability of the neurovascular unit with the development of cerebral edema. Because an increasing number of acute stroke patients are treated with tPA, it is important to know the mechanisms of harmful effects of tPA on the ischemic brain. Here, the best studied pathways of tPA neurotoxicity are discussed along with future directions for a safer use of tPA as a thrombolytic agent in the setting of acute ischemic stroke. | 18,963,068 |
Determination of ascorbic acid with o-iodosobenzoate: analysis of mixtures of ascorbic acid with methionine and cysteine or glutathione. | Ascorbic acid has been determined in pure solutions, pharmaceutical preparations, food-stuffs and biological fluids by titration with o-iodosobenzoate, with visual or photometric detection of the end-point, with leuco-2,6-dichlorophenolindophenol plus potassium iodide as indicator. Cysteine and glutathione, which interfere quantitatively, are masked by cyanoethylation; the cyanoethylated product and methionine have been determined with o-iodosobenzoate in the presence of acidified potassium bromide, with Methyl Red as indicator. Procedures are given for the analysis of mixtures of ascorbic acid with sulphur-containing amino-acids. | 18,963,074 |
Analytical reactions of substituted pyrimidines. | Analytical aspects of the chemistry of substituted pyrimidines are reviewed. | 18,963,090 |
Adsorption of the silver ion on soda-glass-I. | A study of the adsorption of silver ions on soda-glass, using a radiochemical technique, has been made, and the effects of time and temperature investigated. A simple kinetic treatment allows estimation of the rate constants for the adsorption and desorption processes. | 18,963,103 |
The total emulation of the intel 8080 instruction set on a mainframe computer. | A software system, ASSIM-8080, has been developed to permit the writing and debugging of Intel 8080 assembly-language programs with the aid of mainframe computers. ASSIM-8080 will assemble, with error checking and error diagnostics, an assembly-language program. If no errors are found in the source code, ASSIM-8080 will then simulate the execution of the assembly program. ASSIM-8080 will recognize a number of special instruction codes designed to simplify programming and debugging. | 18,963,111 |
Diffuse-reflectance spectroscopy in the infrared. | The theory, and the problems encountered in the development of diffuse-reflectance spectroscopy in the infrared region as an analytical technique, are reviewed. The introduction of Fourier-transform infrared spectrometers has eliminated the difficulty of detecting small scattered intensities, and diffuse-reflectance measurement is now a routine method. The first commercial instruments are now available. | 18,963,120 |
Development of a high-resolution inductively-coupled argon plasma apparatus for derivative spectrometry and its application to the determination of hafnium in high-purity zirconium oxide. | A high-resolution apparatus for inductively-coupled plasma emission spectrometry (ICPES) has been developed, based on an echelle spectrometer modified for wavelength modulation with a quartz refractor plate. The selectivity of the technique is thus improved, and small amounts of hafnium in high-purity zirconium oxide can be determined directly without prior separation or preconcentration. A straight-line calibration curve passing through the origin is obtained without any correction for the interference from zirconium which exists in large excess. The detection limit for hafnium is 0.06 microg/ml, and the relative standard deviation (10 replicates) for hafnium at the 1.2 microg/ml level is about 3%. | 18,963,122 |
Observations on 1-phenyl-3-methyl-4-trifluoroacetylpyrazolone-5, a promising extracting agent. | A simple procedure for obtaining 1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5 (HPMTFP), a promising metal extractant, is described. Recrystallization studies reveal that only one tautomer can be isolated, sometimes with one molecule of water of crystallization, contrary to reports that a yellow enol and a white keto tautomer can be obtained from n-hexane and aqueous ethanol respectively. The melting points and colours of some of the metal chelates of HPMTFP are tabulated and in the case of Hg(II) and Cu(II) chelates, differ from those reported by others. Solubility data for some of the metal chelates of HPMTFP are also given. | 18,963,127 |
Determination of tungsten in complex sulphide ore concentrates. | Determination of tungsten as the thiocyanato complex after separation as the alpha-benzoin oximate complex has been satisfactorily applied to a standard steel and a complex sulphide ore concentrate containing tungsten associated with considerable amounts of Mo, Cu, Bi, As, Pb, Zn, Fe and Sn. | 18,963,148 |
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