Phenol colorimetric method

The CDP is hydrolyzed by sulfuric acid and the gained CD is colored with phenol and the CD content is determined by spectrophotometer. This method is suitable for most of the CDPs except that the substrate is starch or the similar polysaccharides. The detailed operation is as follows  

Different concentration glucose standard solutions (1 mL) is pipetted into the test tube with plug. 1 mL distilled water, 1 mL phenol solution (8%) and 5 mL of sulfuric acid were added respectively, fiiUy mixed, allowed to stand for 10 min and vibrated. Then it was put in water (25°C to 30°C) for 20 min. The solutions shows gradually deepened orange color according to the concentration from low to high. Absorbency value was determined and standard curves were drawn. 

By accurately weighing a certain amount of CDP with the same operation method, we can determine the absorbency value and calculate the CD content according to the standard curve. 

The polymer degree of crosslinking or apparent immobilization quantity can be calculated according to the calculated CD content. 

---

Colorimetric Methods. Numerous colorimetric methods exist for the quantitative determination of carbohydrates as a group (8). Among the most popular of these is the phenol—sulfuric acid method of Dubois (9), which rehes on the color formed when a carbohydrate reacts with phenol in the presence of hot sulfuric acid. The test is sensitive for virtually all classes of carbohydrates. Colorimetric methods are usually employed when a very small concentration of carbohydrate is present, and are often used in clinical situations. The Somogyi method, of which there are many variations, rehes on the reduction of cupric sulfate to cuprous oxide and is appHcable to reducing sugars. 

In the past, the reduction of metallic ions and certain diazotised organic compounds by hindered phenols has served as the basis for colorimetric methods of analysis [112-114],... 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

Emmet [301] developed a colorimetric method involving chlorination of the urea with hypochlorite, followed by condensation with phenol. The limit of detection for this method was 0.2 p,g/l as nitrogen. The method was easily adaptable to automatic analysis. 

The evalnation of phenolic snbstances in wine is a historical topic, and colorimetric methods were developed at hrst for qnality control of wine. Nowadays, it is still performed, and a parameter named optical density is still measnred as an index of color, while other indices have been developed for a rapid evalnation of phenolic componnd content. Moreover, the form of some phenolic compnnds (mono- or diglncoside) is nsed to distingnish between wines obtained by the fermentation of the jnice of Vitis vinifera or Vitis rupestris. 

Being a phenolic compound, isoxsuprine has been determined by a diversity of colorimetric methods. A colorimetric method was described for its determination in dosage forms, based on treatment with the nitrating mixture composed of 1 1 sulfuric and nitric acids [13], This mixture is heated at 100°C for 20 minutes, followed by the addition of acetone and NaOH. The yellow color produced is quantitated on the basis of its absorbance at 384 nm. 

The colorimetric method based on the reagents of Folin and Denis or of Folin and Ciocalteu has been generally preferred over other methods to determine total phenols in complex natural materials such as wines and fruits (1, 2, 3, 4, 5). This method is relatively simple, convenient, reliable, generally applicable, and it is accepted as an official analysis in several countries for total phenols in wines and a number of other products. Although it is a preferred method, it can be even better than is commonly recognized. 

One of the more important areas of use of ultraviolet instruments is the identification and determination of biologically active substances. Many components in body fluids can be determined either directly or through colorimetric methods. Drugs and narcotics can be measured both in the body as well as in formulations. Vitamin assay is another related activity. Nearly all metals and nonmetals can be determined through their ultraviolet absorption or by colorimetric methods. In recent years, ultraviolet instruments have been used extensively for the determination of air and water pollutants, such as aldehydes, phenolics, and ozone ... 

Regarding these uncertainties the agreement of phenol alcohols found in kraft lignin with FeCl3 test and other methods is very reassuring. This colorimetric method is less applicable for M.W.L. preparations in which only a small amount of phenol alcoholic groups can be formed. 

Folin, O., and Denis, W., 1915, A colorimetric method for the determination of phenols (and phenol derivatives) in urine, J. Biol. Chem. 22 305-308. 

The total phenolic compounds in an aqueous sample can be determined by a colorimetric method using 4-aminoantipyrine. This reagent reacts with phenolic compounds at pH 8 in the presence of potassium ferricyanide to form a colored antipyrine dye, the absorbance of which is measured at 500 nm. The antipyrine dye may also be extracted from the aqueous solution by chloroform. The absorbance of the chloroform extract is measured at 460 nm. The sample may be distilled before analysis for the removal of interfering nonvolatile compounds. The above colorimetric method determines only ortho- and meta-substituted phenols and not all phenols. When the pH is properly adjusted, certain para-substituted phenols, which include methoxyl-, halogen-, carboxyl-, and sulfonic acid substituents, may be analyzed too. 

Caillet, S., Salmieri, S., and Lacroix, M. (2006). Evaluation of free radical-scavenging properties of commercial grape phenol extracts by a fast colorimetric method. Food Chem. 95,1-8. 

The progress of the reaction was followed by monitoring the decrease in formaldehyde concentration with time. Previous studies used the hydroxylamine hydrochloride method of analysis (5 -55), but this was avoided in the current study as it requires tedious pH titrations. Instead, a colorimetric method was used that was first developed by Nash (55), involving formation of 3,5-diacetyl-1,4-dihydrolutidine, by reaction of formaldehyde with ammonia and acetyl acetone at neutral pH. The cyclic product absorbs at 412 nm with a molar extinction coefficient of 8,000 (55). Other colorimetric methods cannot be used as they all involve very strongly acidic or basic media (55), which would force the phenol-formaldehyde reaction to completion. 

Halliwell (1978) proposed aromatic hydroxylation as an assay for OH radical production. Hydroxylated products are quantitated using a colorimetric method that measures o-dihyric phenols. The assay has since been improved by Richmond et al. (1981) and has often been used as a simple test tube assay of OH formation (Halliwell et al., 1988) in activated phagoctic cells, isolated hepatocytes, soluble en-... 

DPS and ethanol contents were determined by gas chromatography and the phenol content by a colorimetric method. DPS analysis was done in a column (4 mm x 3 m)... 

To date, both qualitative and quantitative judgments of the individual phenolic compounds in TBV are still unsatisfactory. The phenols in TBV were first studied in terms of their overall content by colorimetric methods and GC-MS techniques by Plessi et al. (2006) and by means of colorimetry alone by Verzelloni et al. (2007). The latter showed that the overall amount of the phenolic compounds is strictly related to the antioxidant properties of TBV. Phenols take part in the polymerization reactions during the TBV aging (Tagliazucchi et al., 2008 Verzelloni et al., 2007) and probably the reactions start during the cooking of the must. 

Anaerobic Metabolism, To examine the extent of anaerobic chloroaromatic metabolism, we undertook a study in which sediments from the upper Hudson River, the lower Hudson River, and the East River were used as inoculum (33, 34). Each monochlorophenol isomer (2-, 3-, and 4-chloro-phenol, CP) and each monochlorobenzoate isomer (2-, 3-, and 4-chloroben-zoate, CB) was used as substrate. Duplicate or triplicate cultures were established under three anaerobic conditions denitrifying, sulfidogenic, and methanogenic. The initial concentration of each of the chloroaromatic compounds was 0.1 mM incubation was at 30 °C in the dark. Substrates were quantified by high-pressure liquid chromatography N2 and CH4 were analyzed by gas chromatography nitrate and sulfate were determined by colorimetric methods or by ion chromatography (33, 34). 

Phenol and the three dihydroxybenzenes (20, 42, 66) in water were determined by LLE with a hydrophilic solvent followed by amperometric titration. LOD was in the ppm range . A dual electrode in a FIA system has been used as detector for total phenols in wastewater. The upstream coulometric electrode has a large surface area and is used to eliminate compounds that cause interference and the second one is an amperometric electrode for oxidative detection of all phenols. Optimal results were found working with a phosphate buffer at pH 6.8, at potentials of +0.35 V and +0.78 V for the coulometric and amperometric electrodes, respectively. A high sample throughput of 60 per hour can be attained with RSD of 0.1-4%. This method is more reliable than the colorimetric method . The concentration of fenobucarb (142) in drinking water was determined after a short alkaline hydrolysis, and oxidation of the resulting 2-s-butylphenol with a GCE at 750 mV, pH 3.5 LOD was 3.6 x 1Q- M, RSD 3.74% for 1 x IQ- M (n = 11, p = 0.05)37 . 

To create a fast and simple method for monitoring of human exposure to neuropathic OPs, a principal new approach to NTE activity analysis has been developed in joint study of the Institite of Physiologically Active Compounds Russian Acad. Sci. and Chemical Department of Moscow State University [88,91,92], Recently, a new biosensor for NTE assay was introduced using a tyrosinase carbon-paste electrode to detect phenol produced by the hydrolysis of phenyl valerate. In this type biosensor phenol is quantified by measuring electroreduction of the generated o-quinone on a graphite electrode (Fig. 6) [88,91 ]. The tyrosinase carbon-paste electrode improved the sensitivity of the NTE assay 10-fold compared to the colorimetric method or an earlier amperometric technique based on oxygen detection [92]. Moreover, the new electrode operates in a... 

R3. Rai, K. B., Sharma, K., and Pattabiraman, T. N., A short-duration colorimetric method based on phenol-sulfuric acid reaction for the estimation of glucosylhemoglobin. Bio-chem. Med. 31, 65-72 (1984). 

The product, arbutin, was identified by chromatographic and colorimetric methods. A large variety of di- and tri-phenols (but no monophenols) could substitute for hydroquinones as acceptors in the purified-enzyme system presumably, the enzymes using monophenols as substrates had been lost during purification. 

---