AN IMPROVED METHOD FOR THE DETERMINATION OF PHOSPHATE BY PHOTOELECTRIC COLORIMETRY

1938 ◽  
Vol 16b (3) ◽  
pp. 97-108 ◽  
Author(s):  
W. J. Dyer ◽  
C. L. Wrenshall
Keyword(s):  
Organic Matter ◽  
Accurate Method ◽  
Improved Method ◽  
Color Intensity ◽  
Soil Extracts ◽  
Color Development ◽  
Light Filters ◽  
Photoelectric Colorimeter ◽  
Made In

A sensitive and accurate method for the determination of phosphate, involving the application of the Evelyn photoelectric colorimeter to the ceruleomolybdate reaction, is described. This technique makes it possible to differentiate phosphate phosphorus from other forms of phosphorus.Conditions affecting the rate and extent of color development have been studied. The results show that the maximum color intensity is developed m about five minutes after addition of the reducing agent. The determination may be made in the presence of extraneous color, and soil organic matter does not interfere with the reaction. Under the conditions specified, using light filters, Beer's law applies to the reaction in soil extracts as well as in pure solutions in the range 0.02 to 0.40 parts per million of phosphorus.

Spectrophotometric Determination of Thiabendazole in Feeds

1965 ◽  
Vol 48 (2) ◽  
pp. 288-295
Author(s):  
C R Szalkowski ◽  
J Kanora
Keyword(s):  
Hydrogen Sulfide ◽  
Spectrophotometric Determination ◽  
Coefficient Of Variation ◽  
Zinc Dust ◽  
Improved Method ◽  
Subsequent Oxidation ◽  
Color Development ◽  
Thiazine Dye

Abstract An improved method has been developed for thiabendazole in feeds. Thiabendazole is extracted from the feed with 0.2N HCl in 50% methanol; interfering substances are removed by making the extract alkaline and extracting into chloroform. The thiabendazole is re-extracted with dilute HCl; the solution is reduced with zinc dust in the presence of p-phenylenediamine to form a hydrogen sulfide complex. After subsequent oxidation with ferric solution to form a thiazine dye, the dye is extracted into n-butanol and measured at 605 mμ. More than 30 commercial unmedicated cattle and swine feeds show an apparent thiabendazole content of 0.00006–0.00044%. Recoveries on feeds made to contain 0.0025–10.0% thiabendazole ranged from 97.6 to 106.6%, with a coefficient of variation of 2.44%. In studies of 30 other drugs added to feeds, only nithiazide, Enheptin, and sulfathiazole interfere. Many variables involved in the color development were studied. The method gives the most accurate and reproducible results on solutions containing 0.2–2.0 μg thiabendazole/ml.

PHOTOMETRIC STUDIES ON THE DIAZO REACTION FOR SERUM BILIRUBIN

1952 ◽  
Vol 30 (6) ◽  
pp. 552-560
Author(s):  
F. D. White ◽  
Dorothea Duncan
Keyword(s):  
Sodium Salt ◽  
Calibration Curve ◽  
Serum Bilirubin ◽  
Alcohol Solution ◽  
Color Intensity ◽  
Color Formation ◽  
Color Development ◽  
Beer's Law ◽  
Beer’S Law

Photometric studies on the Malloy-Evelyn procedure for the determination of serum bilirubin have shown that the azobilirubin color intensity obtained when the diazo reagent acts for 30 min. upon a known amount of bilirubin added to serum in the form of the sodium salt is less than when the reaction takes place with the same amount of bilirubin in chloroform-alcohol solution. This suggests that the usual calibration curve prepared from bilirubin in chloroform-alcohol solution, when used as standard for serum bilirubin determinations, may give values which are about 10% less than the true bilirubin content of the serum. It has also been shown that with the 1 : 10 dilution of the Malloy-Evelyn procedure the azobilirubin from icteric sera does not obey Beer’s law beyond a serum bilirubin content of 15 mgm. per 100 ml. Evidence is submitted that the rate of azobilirubin color formation can be markedly accelerated by increasing the strength of the diazo reagent, and a new reagent is proposed by the use of which the time of color development can be reduced from 30 min. to 5 min.

AN ULTRAMICRO METHOD FOR QUANTITATIVE DETERMINATION OF AMINO ACIDS

1952 ◽  
Vol 30 (8) ◽  
pp. 581-591 ◽  
Author(s):  
Eunice F. Wellington
Keyword(s):  
Amino Acids ◽  
Quantitative Method ◽  
Environmental Temperature ◽  
Complete Oxidation ◽  
Two Dimensional ◽  
Color Intensity ◽  
Color Development ◽  
Concentration Time

A simple, quantitative method for determination of amino acids in about 300 µgm. protein is described. The amino acids are separated by two-dimensional paper chromatography. The chromatograms are sprayed with 2% ninhydrin and the color is developed under controlled and standardized conditions. The colored areas are cut out, eluted, and the color intensity is read in a photometer. The following factors have been shown to affect the color reaction of ninhydrin with amino acids on paper chromatograms: the quality of the ninhydrin; its concentration; time of color development; and the environmental temperature and humidity. Complete oxidation of the hydrolyzate is necessary for accurate quantitative determinations of cysteine, cystine, glutamic acid, aspartic acid, methionine, and valine. Strict standardization of the length of the solvent run is also important for reproducibility in the analyses of some amino acids.Bovine serum albumin has been analyzed by this method and the results found to be in excellent agreement with previously published values.

THE DETERMINATION OF NITRATES IN COLORED SOIL EXTRACTS

1949 ◽  
Vol 27b (2) ◽  
pp. 76-80 ◽  
Author(s):  
F. J. Sowden ◽  
H. J. Atkinson
Keyword(s):  
Hydrochloric Acid ◽  
Acid Solution ◽  
Sodium Hydroxide ◽  
Steam Distillation ◽  
Sodium Hydroxide Solution ◽  
Soil Extracts ◽  
Satisfactory Method ◽  
Photoelectric Colorimeter ◽  
Coloring Matter

In highly colored soil extracts, it was found impossible to determine nitrates directly by the phenoldisulphonic acid color reaction. Attempts to remove the coloring matter by oxidation or absorption were not successful. The most satisfactory method was found to be reduction of the nitrate to ammonia with Devarda's alloy in 0.1 N sodium hydroxide solution in the cold after the removal by steam distillation, of any ammonia that might be present in the extract. The ammonia formed from the nitrate was steam distilled into 0.01 N hydrochloric acid solution and determined colorimetrically by Nessler's reagent using a Klett–Summerson photoelectric colorimeter. The recovery of nitrates from the colored solutions and from standards was satisfactory. The aliquot taken for the determination should contain not more than 0.125 mgm. nitrogen as nitrate.

The quantitative comparison of experimental and simulated diffraction contrast images

1995 ◽  
Vol 53 ◽  
pp. 102-103
Author(s):  
Stuart McKernan
Keyword(s):  
Image Processing ◽  
Personal Computer ◽  
Close Agreement ◽  
Quantitative Comparison ◽  
Image Simulation ◽  
Computing Power ◽  
Diffraction Contrast ◽  
Simulated Images ◽  
Made In

For many years the concept of quantitative diffraction contrast experiments might have consisted of the determination of dislocation Burgers vectors using a g.b = 0 criterion from several different 2-beam images. Since the advent of the personal computer revolution, the available computing power for performing image-processing and image-simulation calculations is enormous and ubiquitous. Several programs now exist to perform simulations of diffraction contrast images using various approximations. The most common approximations are the use of only 2-beams or a single systematic row to calculate the image contrast, or calculating the image using a column approximation. The increasing amount of literature showing comparisons of experimental and simulated images shows that it is possible to obtain very close agreement between the two images; although the choice of parameters used, and the assumptions made, in performing the calculation must be properly dealt with. The simulation of the images of defects in materials has, in many cases, therefore become a tractable problem.

Sign in / Sign up

Export Citation Format

Share Document