Electrometric studies on molecular complexes. Part 1. Biamperometric study of some molecular complexes of iodine

1986 ◽  
Vol 64 (12) ◽  
pp. 2371-2375
Author(s):  
Ram Adhar Singh
Keyword(s):  
Recent Literature ◽  
Equilibrium Constants ◽  
Molecular Complexes ◽  
The Other ◽  
Separate Determination ◽  
Simple Method ◽  
Dissociation Equilibrium ◽  
Present Technique ◽  
Good Agreement

A simple method for separate determination of thermodynamic parameters of molecular complexes in solution is reported. It is based on a polyiodide dissociation equilibrium in conjunction with the biamperometry. The equilibrium constants and the enthalpies determined by this method are in good agreement with the recent literature data, lending support for the applicability of the method. The advantages of the present technique over the other have been outlined.

Determination of Small Bone Particles in Meat

1968 ◽  
Vol 51 (6) ◽  
pp. 1175-1177 ◽  
Author(s):  
Robert M Hill ◽  
B D Hites
Keyword(s):  
Carbon Tetrachloride ◽  
Meat Products ◽  
The Other ◽  
Small Particles ◽  
Bone Content ◽  
Bone Particles ◽  
Small Bone ◽  
Good Agreement

Abstract Very small particles of bone can be separated from ground meats and meat products by the following procedure: The bulk of the meat is solubilized by digestion with papain and the bone is separated from the other nondigestible material according to its ability to settle in a carbon tetrachloride: acetone mixture. Turkey samples with widely varying bone content were analyzed, with good agreement between duplicate samples.

Comparison of Sample Preparation Methods for Phosphorus in Grains and Stock Feeds

1968 ◽  
Vol 51 (4) ◽  
pp. 771-773
Author(s):  
Aaron E Rash
Keyword(s):  
Sample Preparation ◽  
Perchloric Acid ◽  
Sodium Molybdate ◽  
The Other ◽  
Acid Digestion ◽  
Preparation Methods ◽  
Commercial Feeds ◽  
Sample Preparation Methods ◽  
Good Agreement

Abstract The nitric-perchloric acid digestion, 22.070(b) and 22.073, for the determination of phosphorus in grains and stock feeds was compared with three other methods of sample preparation (destruction of organic material) : quinoline molybdate precipitation, perchloric-sulfuric-sodium molybdate digestion, and the plant method. The values obtained by the nitric-perchloric acid method were not in good agreement with those obtained by the other methods studied. Six samples of commercial feeds and one barley sample were analyzed. The barley sample gave very poor recoveries by method 22.073.

A simple method for separate determination of the main 17.21-Dihydroxy-20-Ketosteroids

1969 ◽  
Vol 25 (2) ◽  
pp. 243-246 ◽  
Author(s):  
E.W.M.G. Pieterse ◽  
R.J.H. Scholtis ◽  
N.A. Schmidt
Keyword(s):  
Separate Determination ◽  
Simple Method

Atrazine hydrolysis in aqueous suspensions of humic acid at 25.0 °C

1988 ◽  
Vol 66 (10) ◽  
pp. 2605-2617 ◽  
Author(s):  
Donald S. Gamble ◽  
Shahamat U. Khan
Keyword(s):  
Humic Acid ◽  
Rate Constant ◽  
Free Acid ◽  
Equilibrium Constants ◽  
Environmental Research ◽  
Separate Determination ◽  
Sorption Equilibrium ◽  
Catalytic Sites ◽  
Free Acid Form

The acidic properties of a Chernozemic humic acid were determined by equilibrium titration. The number of carboxyl groups is 2.828 (mmol/g) ± 0.5%. The results were used for an investigation of Brönsted acid catalysis of atrazine hydrolysis by a suspension of the humic acid. There is sufficient sorption so that the rates of change of atrazine and product hydroxyatrazine in solution differ both from each other and form the rate of atrazine conversion on the catalytic sites. An important objective of this work was the separate determination of the sorption equilibrium constants for atrazine and hydroxyatrazine, and the rate constant for atrazine conversion on the catalytic sites. All three constants are relevant to environmental research. The apparent rate constants for changes in solution are experimental artifacts however, not useful for such research. Calculated in terms of carboxyl sorption sites in the free acid form, the sorption equilibrium constants were 1.74 × 102, σ = 0.03 × 102 and 8.5 × 102, σ = 2.3 × 102, for atrazine and hydroxyatrazine, respectively. The rate constant for conversion on catalytic sites ranges from 1.8 × 10−1day−1 ± 20% to 2.9 × 10−1day−1 ± 20%, for atrazine coverage of sites from 9.0(μmol/g) to 1.0(μmol/g).

scholarly journals Two particle picking procedures for filamentous proteins: SPHIRE-crYOLO filament mode and SPHIRE-STRIPER

2020 ◽  
Author(s):  
Thorsten Wagner ◽  
Luca Lusnig ◽  
Sabrina Pospich ◽  
Markus Stabrin ◽  
Fabian Schönfeld ◽  
...  
Keyword(s):  
Neural Network ◽  
Deep Neural Network ◽  
Molecular Complexes ◽  
High Accuracy ◽  
The Other ◽  
Line Detection ◽  
Data Sets ◽  
Detection Approach ◽  
Selection Of

AbstractStructure determination of filamentous molecular complexes involves the selection of filaments from cryo-EM micrographs. The automatic selection of helical specimens is particularly difficult and thus many challenging samples with issues such as contamination or aggregation are still manually picked. Here we present two approaches for selecting filamentous complexes: one uses a trained deep neural network to identify the filaments and is integrated in SPHIRE-crYOLO, the other one, called SPHIRE-STRIPER, is based on a classical line detection approach. The advantage of the crYOLO based procedure is that it accurately performs on very challenging data sets and selects filaments with high accuracy. Although STRIPER is less precise, the user benefits from less intervention, since in contrast to crYOLO, STRIPER does not require training. We evaluate the performance of both procedures on tobacco mosaic virus and filamentous F-actin data sets to demonstrate the robustness of each method.

Cefoxitin interferes with the "Clini-Skreen" column method for urinary 17-hydroxycorticosteroids.

1987 ◽  
Vol 33 (7) ◽  
pp. 1219-1222
Author(s):  
M H Kroll ◽  
A J Jackson ◽  
R J Elin
Keyword(s):  
Aqueous Solutions ◽  
Absorption Spectra ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Molar Absorptivity ◽  
The Other ◽  
Absorbance Maximum ◽  
Column Method ◽  
Apparent Concentration

Abstract Cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids. The apparent concentration of hormone is increased from three- to 10-fold in samples from patients receiving cefoxitin when the Amberlite XAD-2 "Clini-Skreen" column is used. To determine the mechanism of interference, we reacted aqueous solutions of cefoxitin, cortisol, cortisone, and 11-deoxycortisol with phenylhydrazine; recorded the adsorption spectra; and determined the molar absorptivities and the equilibrium and rate constants. Also, we recorded the absorption spectra of phenylhydrazine with eight other cepha antibiotics and benzylpenicillin. Cortisol, cortisone, 11-deoxycortisol, and cefoxitin react with phenylhydrazine and absorb light with superimposable spectra and absorption maxima of 410 nm. The other antibiotics react with phenylhydrazine but absorbance maxima of the products vary, none being at 410 nm. Cortisol, cortisone, and 11-deoxycortisol react with phenylhydrazine 35-fold faster, have equilibrium constants ninefold greater, and have molar absorptivities 1.6 times that of cefoxitin. Thus, cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids by forming a chromophore with the same absorbance maximum and with a molar absorptivity similar to cortisol, but much more slowly.

A Simple Method for Separate Determination of Delta4- and Delta1,4-Corticosteroids in Urine

1971 ◽  
Vol 17 (3) ◽  
pp. 161-165 ◽  
Author(s):  
Tetsuo Uete ◽  
Noriko Shimano
Keyword(s):  
Sulfuric Acid ◽  
Ultraviolet Light ◽  
Absorption Maximum ◽  
Methylene Chloride ◽  
Bathochromic Shift ◽  
Ultraviolet Absorption ◽  
Isosbestic Point ◽  
Separate Determination ◽  
Simple Method

Abstract Ethanolic solutions of Δ4- and Δ1,4-3-ketosteroids absorb ultraviolet light most strongly in the region of 240 nm, but, as sulfuric acid is added in increasing concentrations, absorption decreases. With sulfuric acid concentrations greater than 40 ml/100 ml of ethanol, the Δ4-3-ketosteroids show an absorption peak at about 290 nm, giving an isosbestic point in the region of 275 nm. However, Δ1,4-3-ketosteroids develop the absorption maximum at around 260 nm with the isosbestic point in the region of 250 nm. This bathochromic shift in ultraviolet absorption was used to separately determine Δ4- and Δ1,4-corticosteroids in urine. Urine is extracted with chloroform or methylene chloride. The extract is purified by chromatography and dissolved in H2SO4:ethanol(1:1, by volume). Ultraviolet absorption is measured at 220, 260, and 300 nm for Δ1,4-corticosteroids such as prednisolone or prednisone; at 250, 290, and 330 nm for Δ4-corticosteroids. The readings are corrected by Allen’s method [J. Clin. Endocrinol. Metab. 10, 71 (1950)] and the amount of steroid is estimated.

scholarly journals Kinetic Spectrophotometric Method for the Determination of Ranitidine and Nizatidine in Pharmaceuticals

2002 ◽  
Vol 85 (6) ◽  
pp. 1316-1323 ◽  
Author(s):  
Mohamed I Walash ◽  
Fathalla Belal ◽  
Fawzia Ibrahim ◽  
Mohamed Hefnawy ◽  
Manal Eid
Keyword(s):  
Spectrophotometric Method ◽  
Reaction Pathway ◽  
Kinetic Method ◽  
Fixed Time ◽  
Borate Buffer ◽  
The Other ◽  
Average Recovery ◽  
Kinetic Spectrophotometric ◽  
Good Agreement

Abstract An accurate and simple kinetic method is described for the determination of ranitidine and nizatidine in pure form and in pharmaceuticals. The method is based on the reaction of the compounds with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole in pH 7.4 borate buffer at 60°C for a fixed time of 25 min for both compounds. The absorbance of the reaction product is measured at 495 nm for ranitidine and nizatidine. Calibration graphs were linear over the concentration range of 2–20 μg/mL, with limits of detection of 0.13 (3.7 × 10−7M) and 0.25 μg/mL (7.5 × 10−7M) for ranitidine and nizatidine, respectively. The proposed method was applied successfully to the determination of ranitidine in tablets and ampoules with average recoveries of 100.26 ± 0.69 and 100.29 ± 0.59%, respectively, and to the determination of nizatidine in capsules with an average recovery of 104.26 ± 0.44%. The results obtained are in good agreement with those obtained by the other methods used for comparison. A proposal of the reaction pathway is also presented.

Interaction entre les réactifs lanthanidiques et les bases de Lewis: Application à l'analyse conformationnelle d'alcools cyclohexaniques

1979 ◽  
Vol 57 (9) ◽  
pp. 1080-1088 ◽  
Author(s):  
James Bouquant ◽  
Alain Maujean ◽  
Josselin Chuche
Keyword(s):  
Conformational Equilibrium ◽  
Equilibrium Constants ◽  
Intrinsic Parameters ◽  
Tertiary Alcohols ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Physicochemical Methods ◽  
First Time ◽  
Good Agreement

A method for the determination of the intrinsic parameters K and Δ for lanthanide–substrate complexes has been extended to conformationally mobile molecules. These parameters, determined for a series of secondary cyclohexane alcohols (cyclohexanol and 2-methylcyclohexanol) and for tertiary alcohols (1-methylcyclohexanol and 1-ethylcyclohexanol) complexed with Eu(DPM)3 and Yb(DPM)3 lead to the determination of the conformational equilibrium constants between) the free species on one part and the complexed species on the other.The results obtained for the free species are in good agreement with those obtained by other physicochemical methods. For the complexed species an appreciable shift of conformational equilibrium is noted for low values of the association constants.For the first time, the tert-butyl group of Yb(DPM)3 has been used as a conformational probe. [Journal translation]

CORRELATED STUDIES ON PLASMA FREE CORTICOSTERONE AND ON ADRENAL STEROID FORMATION RATE IN VITRO

1960 ◽  
Vol XXXIV (IV) ◽  
pp. 513-523 ◽  
Author(s):  
]. van der Vies ◽  
R. F. M. Bakker ◽  
D. de Wied
Keyword(s):  
Sulfuric Acid ◽  
Environmental Change ◽  
Formation Rate ◽  
Rat Plasma ◽  
Rapid Decline ◽  
Simple Method ◽  
Adrenal Steroid ◽  
Present Technique

ABSTRACT The effects of various stimuli on the rate of formation of adrenal cortical hormones in vitro and on the plasma free corticosterone were studied in rats. First, a simple method for the determination of corticosterone in rat plasma is described which is based on the fluorescence of this steroid in sulfuric acid. In contrast to procedures described by other workers the present technique does not require expensive spectro-fluorometers, but can be performed using a simple fluorometric unit consisting of components which are generally available. The results obtained with the two methods have shown that the steroid formation rate in vitro and the plasma free corticosterone increases after formalin stress, environmental change and injection of corticotrophin. Hypophysectomy leads to a marked and rapid decline of adrenal activity in vitro and of the plasma free corticosterone.

Sign in / Sign up

Export Citation Format

Share Document