Adequate chemical methods were needed for determining desoxycholic acid in ox bile in the presence of cholic acid, cholesterol, and fatty acids. Desoxycholic and cholic acids occur in combination, partly with glycine and partly with taurine, as glyco-and taurocholic and glyco-and taurodesoxycholic acids. The linkage between the amino acids and bile acids is of an amide nature.On alkaline hydrolysis the nitrogenous constituents are split off. The liberated desoxycholic acid is extracted from an acid solution with ether and determined colorimetrically with salicylaldehyde. DESOXYCHOLIC acid, Which occurs in ox biles and is made from cholic acid, is used in the synthesis of many important hormones. With the advent of the commercial production of cortisone, it became necessary to have available chemical means of determining desoxycholic acid in various biles and also to control the manufactured and isolated material.The principal bile acids in ox bile are cholic (3,7,12-trihydroxycholanic acid) and desoxycholic acid (3,12-dihydroxycholanic acid) (2). Lithocholic and chenodesoxycholic acids are present in minor amounts. The bile acids are present as the sodium salts conjugated with taurine and glycine, the linkage being of an amide nature. On alkaline hydrolysis the nitrogenous constituents are split off and the desoxycholic acid and cholic acid are liberated {6, 7).
Determination of 2,6-Di-tert-Butyl-4-Hydroxytoluene (BHT): Application to Edible Fats and Oils BHT is a very effective antioxidant for many organic substances such as edible fats and oils. Its wide use either alone or in combination with other antioxidants has indicated a need for a specific and effective method for its quantitative determination to maintain effective control over processing operations and to ensure adherence to regulatory requirements. The method presented is based on separation of BHT from fat or oil by steam distillation and colorimetric determination with a dianisidine-nitrous acid reagent.The method is capable of determining 10 to 200 p.p.m. BHT in the presence of other allowable antioxidants.
An improved method has been developed for thiabendazole in feeds. Thiabendazole is extracted from the feed with 0.2N HCl in 50% methanol; interfering substances are removed by making the extract alkaline and extracting into chloroform. The thiabendazole is re-extracted with dilute HCl; the solution is reduced with zinc dust in the presence of p-phenylenediamine to form a hydrogen sulfide complex. After subsequent oxidation with ferric solution to form a thiazine dye, the dye is extracted into n-butanol and measured at 605 mμ. More than 30 commercial unmedicated cattle and swine feeds show an apparent thiabendazole content of 0.00006–0.00044%. Recoveries on feeds made to contain 0.0025–10.0% thiabendazole ranged from 97.6 to 106.6%, with a coefficient of variation of 2.44%. In studies of 30 other drugs added to feeds, only nithiazide, Enheptin, and sulfathiazole interfere. Many variables involved in the color development were studied. The method gives the most accurate and reproducible results on solutions containing 0.2–2.0 μg thiabendazole/ml.
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