Colorimetric estimation

Bismuth standard solution (quantitative color test for Bi) dissolve 1 g of bismuth in a mixture of 3 mL of concentrated HNO3 and 2.8 mL of H2O and make up to 100 mL with glycerol. Also dissolve 5 g of KI in 5 mL of water and make up to 100 mL with glycerol. The two solutions are used together in the colorimetric estimation of Bi. 

Oil can be deterrnined by extracting the residue using carbon tetrachloride and then evaporating the CCl. Sediment such as iron is deterrnined by dissolving in hydrochloric acid followed by colorimetric estimation. Dissolved noncondensable gases are deterrnined by analysing the atmosphere above the liquid ammonia. 

In all cases where the chemical properties of these preparations have been studied the active material appears to be predominantly carbohydrate in nature, containing in the case of the A factor 50-70% of reducing sugar, 5.7% nitrogen and giving by colorimetric estimations 25-30% of glucosamine on hydrolysis. 

Total flavonoid content. Quantitative analysis of flavonoids depends on the objective of the study. Colorimetric estimation of total flavonoid content is measured by the aluminum chloride colorimetric assay (Jia and others 1999 Chang and others 2002). The total flavonoid content measured in this way is normally expressed in equivalent values of a standard flavonoid, often catechin or quercetin equivalents. Not all subgroups of flavonoids can be quantified by colorimetric methods however, total anthocyanin content is determined using the pH-differentiation method (Boyles and others 1993). 

Strongly basic antibiotics may be precipitated by formation of the coloured reineckate salt which may then be determined spectrophotometri-cally 65. Bickfordl66 dissolved the precipitated neomycin reineckate in acetone and has successfully used this procedure to assay neomycin extracted from topical formulations. Roushdi et al 73 preferred to oxidise the precipitate with potassium permanganate and then colorimetrically estimate the chromate produced with diphenylcarbazide. 

Allen, R. J. L. (1940). Micro-determination of phosphorus. (Colorimetric estimation molybdate blue.) Biochem. J. 34, 858. Bellamy, L. J. (1954). Infra-red Spectra of Complex Molecules. Methuen and Co. 

Burton K (1956) A study of the conditions and mechanism of the diphenylamine reaction for the colorimetric estimation of deoxyribonucleic acid. Biochem. 62 315-323. 

A colorimetric estimation of inserted PEG-phospholipids was developed based on the two-phase system used to quantify phospholipids (49). The formation of a complex between the phospholipids and Fe(SCN)3 transfers the chromophore Fe(SCN)3 to the organic phase, allowing quantification of the phospholipids present in the solution. This system was applied to PEG-phospholipids (50). It is quite sensitive but obviously limited to PEG-phospholipids. The PEG-lipids, which bear no phosphate group, cannot be quantified by this method. 

Nag A, Mitra G, Ghosh P. A colorimetric estimation of polyethyleneglycol-con-jugated phospholipid in stealth liposomes. Anal Biochem 1997 250 35. 

In the colorimetric estimation of p-phenethylbiguanide the plot of readings against concentration is found ipIO) to be a straight line at concentrations less than 10 W. Above this concentration, p-phenethylbi-guanide in solution deviates sharply from Beer s Law. It may be concluded that in the low concentration range over which Beers Law is valid, the compound exists in the monomeric state in aqueous solution. 

Paludrine is cleaved by zinc amalgam and acid to a primary amine (675), which may be diazotised in situ and coupled to 3ueld a dye a colorimetric estimation of Paludrine is based on this reaction sequence. 

O. M. Friedman and E. Boger, Colorimetric estimation of nitrogen mustards in aqueous media. Hydrolytic behavior of bis(2-chloroethyl)amine, nor-HN2. Analytical Chemistry, 1961,33,906-910. 

Selected entries from Methods in Enzymology [vol, page(s)] Colorimetric estimation of vitamin A with trichloroacetic acid, 67,... 

West, P. W., and G. C. Gaeke, Fixation of Sulfur Dioxide as Disulfitomercurate(II) and Subsequent Colorimetric Estimation, Anal. Chem., 28, 1816-1819 (1956). 

The phosphorus content can be determined by wet oxidation of the starch with sulfuric (or nitric) acid and hydrogen peroxide followed by colorimetric estimation of the phosphomolybdate complex. A detailed procedure for gravimetric determination can be found in AACC method 40-57 (AACC, 2000). However, large sample sizes (2-5 g) are required in this method. 

Krisman CR (1962) A method for the colorimetric estimation of glycogen with iodine. Anal Biochem 4 17-23... 

Phosphorus analysis is usually best accomplished via oxidative acid digestion (H2S04/ HC104) of the samples, followed by colorimetric estimation of the phosphorus as phos-phomolybdovanadate.8... 

The total content of RNA + DNA in tissues may be estimated from the phosphorus content or by color reactions of the sugars.37 545 These reactions depend upon dehydration to furfural or deoxyfurfural by concentrated sulfuric acid or HC1 (Eq. 4-4). Furfural formed from RNA reacts with orcinol (3,5-dihydroxy-toluene) and ferric chloride to produce a green color useful in colorimetric estimation of RNA. A similar reaction of DNA with diphenylamine yields a blue color. 

If a drop of 0-02N aqueous sodium sulphide is added to a drop of a solution containing arsenate or phosphate on a filter paper and a drop of aqueous ammonium molybdate acidified with sulphuric acid also added, a blue colour develops 2 ferro- and ferri-cyanides and thiocyanate should be absent. The formation of molybdenum blue is used in the colorimetric estimation of arsenic (see p. 321). 

Recently, in seeking a colorimetric method more sensitive than the Elson-Morgan test (20y), Dische and Borenfreund88 have developed a technique needing only 5y of the amino sugar. The method is based on the deamination of the hexosamine to give the corresponding 2,5-anhydro-hexose with Walden inversion at C2. The anhydro derivatives yield stable characteristic colors when treated with indole in dilute hydrochloric acid, well suited to quantitative colorimetric estimation. 

Maren TH (1967) Carbonic anhydrase Chemistry, physiology, and inhibition. Physiol Rev 47 595-781 Philpot FJ, Philpot JSL (1936) A modified colorimetric estimation of carbonic anhydrase. Biochem J 30 2191-2193 Wistrand PJ, Knuuttila K-G (1980) Bovine lens carbonic anhydrases Purification and properties. Exp Eye Res 30 277-290... 

When an alcoholic solution of diphenylcarbazide, containing a little acetic acid, is added to a very dilute solution of chromic acid, a violet coloration is produced. This has been made the basis of a colorimetric estimation. With more concentrated solutions the reaction gives a reddish-brown colour, and finally a brown precipitate containing about 18 per cent, of chromium. 

West, P.W. and Gaeke, G.C., 1956. Fixation of sulphur dioxide as disulfito-mercurate (II) and subsequent colorimetric estimation. Anal. Chem., 28 1816-1819. 

This is the oldest test, but is still widely used. It depends upon the colorimetric estimation of traces of nitrous acid or nitric peroxide by test papers prepared with potasuum iodide and starch. The explosive is contained in a test tube which is heated to a constant teiT >orature, the test paper being suspended over the explosive. 

Colorimetric Estimation of Phenylalanine in Some Biological Products. 

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