Color test for identification

Two identification tests for oxytetracycline hydrochloride are given in the USP 28 [1], one being an ultraviolet absorption test and the other a color test. European Pharmacopoeia [2], British Pharmacopoeia (BP) 2003 [4], International Pharmacopoeia [5], and Pharmacopoeia of the People s Republic of China [6] described a thin-layer chromatography and color tests for identification of oxytetracycline hydrochloride and oxytetracycline dihydrate. For identification of oxytetracycline calcium, USP 28 [1] used Method II under identification of tetracycline <193>, whilst BP 2003 [4] described a TLC, color test, and calcium test as the method of identification. 

Tauber test (analy chem) A color test for identification of pentose sugars the sugars produce a cherry-red color when heated with a solution of benzidine in glacial acetic acid. tau-bor, test ... 

Tests for Identification of Some Synthetic Dyes. Two very simple reactions can confirm the presence of synthetic dyes. In the solvent stripping test, if the ammonia solution is heavily stained and it becomes irreversibly colorless upon the addition of zinc dust even at room temperature, the presence of an azo dye with sulfo group or groups is indicated (an acid or direct dye) (36, 37). The color of the solution in concentrated sulfuric acid can also be an important indication for identifying synthetic dyes. In this test, a few drops of concentrated sulfuric acid are dripped on a small sample of the dyeing, and the color of the sulfuric acid is observed after a few minutes. Intensive magenta red, red-violet, violet, blue, and green solutions indicate the presence of synthetic dyes (36, 37). 

Physical tests for Identification. Specific density, index of refraction, color, viscosity, and melting point tests are used to identify fats and oils. The onset, flow point, and the temperature range over which melting occurs are indicative of specific numbers in fats. They are determined by standardized procedures. 

As mentioned in Section 1.3 this aryne, the first for which a structural formula was drawn, was postulated to rationalize the cine-substitution observed upon treatment of 3-bromobenzofuran (181) with ethanolic KOH or NaOC2H5 [equation (3)]. A more detailed examination of this oft-cited paper reveals that the primary substitution products 182 and 183 were, in fact, never isolated except perhaps as a mixture containing 26% of the starting material (181). Their identification rests on the observation of characteristic color tests for the benzofuranones 184 and 185 formed after treatment of this mixture with gaseous HCl. The only products actually isolated in pure form from the reac-... 

Testing of phthalocyanines includes crystallization (qv), flocculation, and appHcation in paints, plastics (qv), and printing inks (1). The ASTM standard specifications include CuPc in dry powder form for various appHcations (153). The specifications cover color (qv), character or tint, oil absorption, reactions in identification tests, and dispersions and storage stabiUty. Quantitative deterrninations are possible with ceric sulfate (30) or sodium vanadate (154). Identification methods are given (155), including tests for different appHcations. 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

For identification of oxytetracycline in pharmaceutical preparations, USP 28 [1] describes Method II under identification of tetracycline <193> (see Table 1), BP 2003 [4] describes a TLC and color test. 

When a test sample (comprising a single compd or its mixt with other ingredients) is treated with an appropriate reagent, a coloration is produced which is characteristic of the compd tested. The reaction, so produced, is known as a color reaction and it may serve for identification of the sample. A reagent which produces the coloration is known as a color reagent... 

Reaction XVI. Action of certain Oxidising Agents on a- and jS-Naph-thols. (J. R. C. S., 6, 183.)—If to an aqueous solution of a naphthol a few drops of a neutral aqueous solution of ferric chloride be added, a green coloration is produced, and, after a time, a flocculent precipitate of clinaphthol. Performed in this way on the test tube scale, the reaction is very useful for identification purposes. 

Table 1 lists some of the color tests reported for the identification of oxyphenbutazone. 

Critical limitations are those determining the separation and identification of spots. If a spot remains unresolved in three different solvent systems, it may be considered homogeneous. If its position coincides in these solvent systems with that of a known, run simultaneously, its identity is then considered established. These criteria should, however, be buttressed by as many other criteria of identity as are available, such as highly specific color tests, chemical alteration, or better still, where possible, isolation of the material in quantity sufficient to permit employment of classical identification methods. That there is need for these further criteria was shown by Levine and Chargaff,212 who noted that l-amino-2-hydroxypropane and 2-amino-l-hydroxypropane have the same Rf values in five different solvent systems. 

The following two color tests have been recommended for the identification of dipyridamole [2] ... 

Identification Cautiously dissolve 250 mg of sample in 5 mL of glacial acetic acid, and add a few drops of a saturated solution of potassium iodide. Iodine is liberated. Add 20 mL of water and sufficient sodium thiosulfate TS to remove the iodine color. The resulting solution gives positive tests for Calcium, Appendix IIIA. 

However, despite many attempts,it is only within the last few years that progress has been made toward the successful cyclization of hexose derivatives to inositol derivatives. Ferndndez, Izquierdo and Martinez " have reported the presence of a cyclase in the leaves of Lactuca virosa L. which converts D-glucose to a material giving the Scherer test for inositol. Since this color test is general for the inositols a definite statement regarding the nature of the product will have to await its isolation and identification. 

Add 10 mL of distilled water to the reaction flask, grasp this with a clamp, swirl the mixture over a free flame to dissolve all the product, and cool under the tap. Remove a drop of the solution on a stirring rod, add it to 0.5 mL of a 0.3% solution of ninhydrin in water, and heat to boiling. If any unacetylated DL-alanine is present a purple color will develop and should be noted. Pour the solution into a 20 x 150-mm test tube and rinse the flask with a little water. Add 1.5 mL of concentrated ammonia solution, stir to mix, check the pH with Hydrion paper, and, if necessary, adjust to pH 8 by addition of more ammonia with a Pasteur pipette. Add 10 mg of commercial acylase powder, or 2 mL of fresh acylase solution, mix with a stirring rod, rinse the rod with distilled water, and make up the volume until the tube is about half full. Then stopper the tube, mark it for identification (Fig. 3), and let the mixture stand at room temperature overnight, or at 37°C for 4 h. 

Liquid oral preparations are usually contained in PET or PETG containers. PETG has a different polymeric composition than PET as discussed under Types of Packaging Materials. Physical characteristics are listed in the USP and 21 C.F.R. specifies their composition. Identification of PET and PETG shows that these plastics are distinct and distinguishable from one another by IR spectrum, but the two compounds are similar as evaluated by thermal analysis.f " This type of plastic should be tested for colorant extraction as previously discussed. " ... 

Extrahepatic biliary atresia may involve all or part of the extrahepatic bifiary tree. The gallbladder is usually absent. Involvement of the hepatic or common duct leads to the characteristic syndrome of severe cholestatic jaundice. It occurs in 1 in 10,000 births, with females more commonly affected than males. Jaundice and pruritus usually appear in the first week. Stools are pale and the urine is tea colored. Jaundice is deep, but the aminotransferases are only mildly elevated. If jaundice persists beyond 14 days of age, a direct or conjugated bilirubin measurement must be performed to exclude biliary atresia. If it is elevated, the urine should be tested for bile and the stool color inspected if the color is not green or yellow, biliary atresia is likely. Early identification of this condition is essential if these infants are to benefit fi"om the operation of portoenterostomy, which should be performed no later than 60 days after birth. If portoenterostomy is not successful, liver transplantation is the treatment of choice. Children rarely live beyond 3 years unless the lesion is surgically correctable. 

In addition to instrumental methods of identification, an analyst may make use of some method of microchemical testing. An excellent discussion of the latter is available5. This work is a systematic study of precipitate tests, color tests, and crystal formation for modern analgesics. Through manipulation of the various testing parameters, Clarke identified a large number of analgesics. Even with the sophisticated instrumentation now available, "wet" methods of identification are still very useful. 

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