Of color tests

Kuznetsov (Ref 5) used Na azidodithiocarbonate and its derivs to increase the sharpness of color tests for example, in neutral soln the anhyd Na salt gives a yel color in the presence of Cu. Hofman-Bang (Ref 6) found that dil solns of Ij NaN2 were catalyzed by Na azidodithiocarbonate and proposed a chain reaction mechanism. The Na salt is used primarily to prepare the heavy... 

Determination.—Analytical methods for determination of D-glucuronic acid have been discussed recently by Artz and Osman.6 Decarboxylation is the most accurate method, and is generally used for determination of D-glucuronic acid from plant sources. Some modifications have been introduced recently for small quantities.26 Other methods, such as reduction, measurement of optical rotation, and an array of color tests,27 are of limited value. Levvy28 has applied a cerimetric method using a Conway burette. 

The evaluation of alkaloids content may be effected on the basis of color tests by the Van Urk reaction (Pharm. Weekbled 66, 1929, p. 473) after extraction as follows the culture broth is alkalinized to pH 8 and extracted first with chloroform and then re-extracted with the aqueous acidic solution (e.g., 1% H2S04 or 2% tartaric acid) which is used for the colorimetric analysis of alkaloids. 

In addition to melting point measurements, there are other methods to evaluate or prove the achieved progress in purification. These are gas chromatography, density measurements, or the different types of color tests. 

This paper explains how to use statistical tools to evaluate the reproducibility of color testing. Several pigment chemistries combined with several test methods were evaluated in hopes of establishing a test that both the statistician and color technician would endorse. 

It is often customary to date the emergence of histochemistry from the publication in 1936 of Lison s Histochimie animale. Rapid advances in the qualitative chemistry of organic compounds during the early decades of this century made the 1930 s ripe for the application of color tests and allied methods to tissue sections for the localization of known compounds or at least their functional groups. As early as 1850, however, histologists were attempting to identify specific substances, initially metals, in situ (Pearse, 1951). 

Thus the evidence to date indicates that there might be a scarcely significant relationship between diet and behavior, but the food additive controversy is not yet settled as pointed out in an editorial by Bberman and Furukawa (1978). The antioxidants butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT) have been added to the list of agents which should be avoided, but there is no evidence that they can influence behavior. The amount of color tested is often 100 mg, which usually exceeds the daily intake, especially when taken repeatedly. One should also differentiate between azo dyes and other chemical types of dye. An excellent review of these problems has recently been published by Lipton et al. (1979). 

Advantages and disadvantages of presumptive tests Most presumptive tests are carried out on porcelain tiles. There are a number of clear advantages to tests of this nature they are cheap, quick, and easy to use. They also have the advantage of being portable if required and various road side test kits have been developed on the basis of color tests. 

Some controversy and dd)ate surround the use of microcrystals (ayslal tests) in drug anal) is, but this shouldn t be the case. Properly employed, crystal tests are powerful extensions of color tests. Specificity is derived chiefly from appearance and behavior of crystals under polarized light The catch— and there usually is one— is the user s ability to identify crystal forms. However, there is a subjective element in all judging colors in all color tests, which is addressed by controls, literature validation, experimentation, and experience. The same is true of crystal tests. In fact, prior to the wide availability of instrumentation, crystal tests were considered to be one of the most specific and selective tests available for many drugs. 

Unlike the situation noted for marijuana, the morphology of mushrooms and peyote is normally not used as part of their identification, due to the more complex botanical challenge. The plant-matter matrix of peyote and psilocin mushrooms makes the use of color tests impractical, unless the tests are apphed to the extract. In most cases, ethanol or methanol is the extraction solvent of choice for dried plant matter. Some laboratories heat the methanol prior to extraction. The peyote button, and sometimes mushrooms, must be grotmd with coffee grinders or similar equipment or must be macerated prior to extraction. Cleaning these appliances between uses is crucial to prevent cross-contamination. The extracts are then amenable to TLC and instrumental confirmation by GCMS. 

In addition to the precipitation reagents, a large variety of color-tests is in use for the detection of proteins. (A) In Millon s Reaction, the material is treated with nitric acid, in which a small... 

A wide range of color tests of -arying degrees of aensithity and specificily ha e been reported for the detection of formaldehyde in addition to the two authenticated methods already described. These tests involve the use of phenols, aromatic amine. , alkaloids, and other miscellaneous reagents. 

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