Microcolorimetric Determination Research Articles

High-Resolution, Two-Dimensional Measurement of Dissolved Reactive Phosphorus in Sediments Using the Diffusive Gradients in Thin Films Technique in Combination with a Routine Procedure

Dissolved reactive phosphorus (DRP) is the most available P form in sediments and often directly controls phytoplankton blooms in aquatic systems. In this study, a novel procedure was developed for two-dimensional (2D) measurement of DRP in sediments at a spatial resolution of 0.45 mm using the diffusive gradients in thin films (DGT) technique with a revised high-capacity binding phase (Zr oxide gel). This procedure involves DGT uptake of P in sediments, 2D slicing of the binding gel on a 0.45 × 0.45-mm grid system, elution of P from each gel square with 1 M NaOH, and microcolorimetric determination of DRP in each eluted solution using 384-microwell plates. Measurements of DRP via this procedure were tested in homogeneous solutions and sediments and produced an acceptable error (<20% relative standard deviation) for the analysis once the accumulated mass of P in each gel square reached 1.2 μg cm(-2). This method was successfully applied to produce 2D images of the DRP distribution in sediments with and without the influence of tubificid worm bioturbation, revealing a much more pronounced and localized impact from tubificid worms than that found using a one-dimensional measurement of pore water DRP concentrations at 1-cm resolution.

Micro-colorimetric determination of cholinesterase activity of motor end plates in the rat diaphragm

Abstract A spectrophotometric method is described for the determination of total cholinesterase activity in groups of 3–30 end plates, after staining with copper thiocholine and dissecting from the rat diaphragm, by continuous recording of the yellow colour (412 mμ) produced by reaction between dithiobisnitrobenzoate (1mm) and thiol groups liberated enzymatically from acetylthiocholine (5mm) at pH 7·0. Cholinesterase activity of end plates after correction for muscle ranged from 3·3–22·3 times 10−11m/end plate/hr and muscle cholinesterase activity ranged from 8·8–29·4 times 10−11 μg/hr. 2·9–26·7% of measured end plate cholinesterase activity was attributable to muscle. The results for end plate cholinesterase agreed with those obtained by other workers using microgasometric techniques. It was calculated that there were approximately 3·6 times 106 cholinesterase active sites/end plate which compared closely with 6 times 106 molecules acetylcholine released/ nerve ending/impulse and 2·6 times 106 cholinergic receptors/end plate given in the literature. It is suggested that each acetylcholine molecule after liberation from a nerve ending may interact with one receptor and be destroyed by one cholinesterase active site.

Micro-colorimetric determination of adenosinetriphosphatase activity in freeze-dried sections of rat diaphragm muscle.

Abstract A technique is described for determination of ATPase activity in 3–30 μg samples dissected from freeze-dried sections of rat diaphragm muscle. Tissue samples are incubated at room temperature with optimal concentrations of ATP (10 mM) and MgSO4 (5 mM) in 0·1 M tris/HCl buffer at pH 7·4. Inorganic phosphate is measured spectrophotometrically. Mean activity for 20 rats was 0·22 ± 0·06 (s.d.) mole-Pi/kg/wet tissue/15 min. Results did not depend on plane of section or section thickness. 5 mM Mg2+, 10 mM Ca2+ and 1 mM 2, 4-dinitrophenol produced maximal ATPase activation and inhibition was obtained with p-chloromercuribenzoic acid (pI503·9) but not chlorpromazine (0·01–0·1 mM). There was no significant evidence of Na+ plus K+ activated ATPase or inhibition with ouabain (5 mM). ATPase activity was uncharacterized and relative contributions of specified muscle ATPase systems were unknown. As an insoluble enzyme system was involved and photomicrographs showed characteristic muscle features in freeze-dried sections, ATPase activity appeared due to enzymic function in situ. Results are discussed in relation to mutual availability of enzymic sites and reagents.

A rapid, quantitative determination of total and free cholesterol with anthrone reagent

A simple, rapid microcolorimetric determination for total and free 3β-hydroxy sterols in serum and tissues has been described. Following extraction of total sterols and saponification of the esterified fraction by established procedures, the sterol is precipitated in 15 min at 45°C as the digitonide using 10% aluminum chloride. The isolated sterol digitonide is purified by twice recrystallizing from methanol-10% aluminum chloride (1 : 1), each step requiring 20 min at 45°C. The precipitate is washed with acetone and suspended in glacial acetic acid, and the digitonin moiety is determined with a stable anthrone reagent. Multiple analyses of sterol concentrations as low as 15–20 μg are routinely determined with an accuracy comparable to the method of Sperry and Webb, and with a greater sensitivity and precision than obtained with the latter method.

Microcolorimetric determination of antimony in organic antimony compounds: Y. Kinoshita, Yakugaku Zasshi, 78, 315-18 (1958)

Microcolorimetric determination of antimony in organic antimony compounds: Y. Kinoshita, Yakugaku Zasshi, 78, 315-18 (1958)

Microcolorimetric Determination of Organic Sulfur by the Tin(II)-Strong Phosphoric Acid Reduction Method

Abstract A simple and rapid method for the determination of minute amounts of organic sulfur was established by using the oxidizing action of chromium (VI)-strong phosphoric acid and the reducing power of tin (II)-strong phosphoric acid. Organic sulfur was oxidized to sulfate by the former in a test-tube of fused silica and the sulfate was reduced to hydrogen sulfide by the latter in the same vessel. The hydrogen sulfide evolved was absorbed in zinc acetate solution and estimated colorimetrically by the ordinary methylene blue method. The absorbancy of the colored solution was measured at 655 mμ with a photoelectric colorimeter using 1-cm. cells. The sulfur content of the sample was estimated by comparing the absorbancy value with the standard curve prepared with sodium sulfate. Some organic compounds containing sulfur were analyzed by this method and satisfactory results were obtained. However, analysis of the miscellaneous organic substances such as biological specimens has not been undertaken and the problems for this purpose remain to be solved in future.

Microcolorimetric Determination of Sulfate by Reduction to Hydrogen Sulfide with Tin(II)—Strong Phosphoric Acid

Abstract A new reagent, “Tin(II)-strong phosphoric acid” has been prepared to permit a rapid and simple determination of sulfate sulfur by reduction to hydrogen sulfide. The procedure for the determination of semi-micro quantities of sulfate sulfur, previously devised by the authors, has been extended to the microgram scale by adopting the sensitive methylene blue colorimetric method. The rapidity and simplicity of the original method are still retained in this new colorimetric method, by which 1 to 35 micrograms of sulfate sulfur can be estimated. The apparatus is very simple, a test-tube of fused silica being employed as the reaction vessel. The standard calibration curve for colori-metric determination of sulfate sulfur by this method coincides well with that drawn for sodium sulfide by direct coloration with p-amino dimethyl aniline and ferric chloride. Interference of other anions can be kept out of consideration, because the sulfate ion is easily separated by addition of barium chloride solution and coprecipit-ation with ferric hydroxide. Large amounts of ferric hydroxide do not affect the method. Some examples of the determination of sulfate sulfur in ferric chloride reagent and Japanese acid clay are described.

Studies on micro-colorimetric determination of phenylacetic acid in biological materials II

Studies on micro-colorimetric determination of phenylacetic acid in biological materials II

Studies on microcolorimetric determination of phenylacetic acid in biological materials. I

Studies on microcolorimetric determination of phenylacetic acid in biological materials. I

Rapid Microcolorimetric Determination of Dissolved Oxygen

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRapid Microcolorimetric Determination of Dissolved OxygenW. F. LoomisCite this: Anal. Chem. 1954, 26, 2, 402–404Publication Date (Print):February 1, 1954Publication History Published online1 May 2002Published inissue 1 February 1954https://doi.org/10.1021/ac60086a037RIGHTS & PERMISSIONSArticle Views152Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (404 KB) Get e-Alerts Get e-Alerts

Micro-colorimetric determination of potassium with dipicrylamine

Determination of potassium in biological solutions such as, blood, urine, milk, plant saps, and soil solutions has become a pressing problem in recent years due to the most important role played by potassium in biochemical processes. Many workers have tackled this problem from different angles. Various methods have been adopted but these were either gravimetric or volumetric ones and involve many tedious and complicated processes. A few years ago Kolthoff and Bendix 1 described the use of dipicrylamine in the gravimetric, volumetric, and colorimetric determination of potassium. Recently E. Amdur adopted the colorimetric procedure to the determination of potassium in tissues and blood.

乳汁内マグネシユームの微量比色定量法

乳汁内マグネシユームの微量比色定量法

Application of the sodium diethyldithiocarbamate reaction to the micro-colorimetric determination of copper in organic substances

Application of the sodium diethyldithiocarbamate reaction to the micro-colorimetric determination of copper in organic substances