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Reagent

About: Reagent is a research topic. Over the lifetime, 60091 publications have been published within this topic receiving 1234928 citations. The topic is also known as: reagens.


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Journal ArticleDOI
TL;DR: The chemistry of the Folin-Ciocalteu is described and two Folin assays (single and dual reagent) are described for the assay of phenols and polyphenols with respect to experimental detail and critically evaluated for pure compounds and for mixtures.
Abstract: Summary of Manual Dual Reagent Procedure [2] Up to100 µL of properly diluted sample in an organic water-mis-cible solvent with at least 6 mL of water + 0.5 mL of F-C reagent (Sigma); wait between 1 - 8 min, add 1.5 mL of Na 2 CO 3 ; mix and bring to 10 mL total volume with water; then measure absorbance The volume can be scaled down to conserve reagents. Abstract The chemistry of the Folin-Ciocalteu is described and two Folin assays (single and dual reagent) are described for the assay of phenols and polyphenols with respect to experimental detail and critically evaluated for pure compounds and for mixtures (plant extracts). The single rea-gent method was found to be more precise and sensitive. The problem of interferences in the Folin assay was evaluated for both methods. Interferences for the dual reagent methodology can be eliminated by a solid phase removal of phenols using a commercial resin (Oasys HLB) or polyvinylpyrrolidone resin (Polyclar AT). A new basic/acid hydrolysis combed with the Polyclar AT was used to measure the total phenols in a sample as previous methods measured only the phenolic groups not bound as ether or ester groups. A semi-automated method, microplate reader, is described as to the experimental procedure and applicability. Miscellaneous uses of the Folin assay including flow injection,urine analysis and a mixed standard are briefly described.

127 citations

Journal ArticleDOI
TL;DR: The Letters to the Editor section is subdivided into four categories: Communications, Notes, Comments, and Errata as discussed by the authors, and the textual material of each Letter is limited to 1200 words minus the following: (a) 200 words for a square figure one column wide.
Abstract: The Letters to the Editor section is subdivided into four categories entitled Communications, Notes, Comments and Errata. The textual material of each Letter is limited to 1200 words minus the following: (a) 200 words for a square figure one-column wide. Larger figures are scaled in proportion to their area. (b) 50 words for each displaved equation; (c) 7 words for each line of table including headings and horizontal rulings. Proof will be sent to authors. See the issue of 1 JulV 1978 for a fuller description of Letters to the Editor.

127 citations

Journal ArticleDOI
TL;DR: In the presence of zinc-dust and titanium tetrachloride, yielding the 1-alkenyl ethers (III) with predominance of the Z-isomers.
Abstract: The esters (I) reacts with the 1,1-dibromoalkanes (II) in the presence of zinc-dust and titanium tetrachloride, yielding the 1-alkenyl ethers (III) with predominance of the Z-isomers.

127 citations

Journal ArticleDOI
TL;DR: Macrolactonization of 3,5- O -(3,4-dimethoxybenzylidene)-9,11-O -(2,4,6-trimethylbenzo-idene)(9 S )-9-dihydroerythronolide A seco-acid (4 ) was reexamined under various conditions and found to proceed rapidly only by treatment of 4 with Yamaguchi's reagent, 2.4, 6-trichlorobenzoyl chloride, in the presence

127 citations

Journal ArticleDOI
TL;DR: The method appears especially suitable for adaptation to discrete mechanical analyzers either of the single channel or the multi-channel type, and can be lowered by a factor of 2.2 by replacing phenol by dihalogen phenols.
Abstract: A fully enzymatic method to determine total cholesterol in serum is described. The method appears especially suitable for adaptation to discrete mechanical analyzers either of the single channel or the multi-channel type. The method uses the enzymes cholesterol esterase (EC 3.1.1.13), cholesterol oxidase (EC 1.1.3.6) and peroxidase (EC 1.11.1.7) with 4-aminophenazone and phenol as substrates in the indicator reaction. The method was adapted to the Greiner Selective Analyzer GSA-II. For this purpose the critical parameters of the reaction were intensively examined. The complete reagent is stable within the GSA II dispenser at 4 degrees C for at least 1 week. By omitting cholesterol oxidase in the blank reagent a sample bland and a partial reagent blank are obtained. Within a range up to 10.4 mmol/1 (4.0 g/l) the maximum colour is developed within 6 minutes. The calibration factor was stable for 4 months. The method allows absolute measurements. At concentrations between 2 and 4 mmol/1 within-batch precision ranged from 0.5 to 1.4%. Precision from day to day for the same control sera amounted to 2.8; 2.0; 2.7 and 2.0% for a period of 3 months. Examination of accuracy yielded satisfying results. Ascorbic acid in the physiological range did not alter results to a significant extent. Catalase or novaminesulfone added in vitro did not interfere. Optical interferences by bilirubin, hemoglobin or turbidity are compensated by a sample blank. A comparison of results with the enzymatic method of Roeschlau et al. (Z. Klin. Chem. Klin. Biochem. 12, 226 (1974)) yielded satisfactory agreement. The limits of detection of the present method can be lowered by a factor of 2.2 by replacing phenol by dihalogen phenols.

127 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20232,117
20224,093
2021785
20201,317
20191,860
20182,158