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4. Chemical Evaluation, Determination of the active constituent in a drug by chemical, , tests is referred to as chemical evaluation., , The following are various methods of chemical evaluation, , Instrumental methods, Chemical tests, Individual constituent chemical tests, , Micro chemical tests

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1.Instrumental methods: They make use of various instruments for, , evaluation like colorimetry, flourimetry spectrophotometry etc., , 2.Chemical constants tests: These are like acid value, iodine value and, , ester value etc are used for the identification of fixed oils and fats., 3.Individual chemical tests: These are the tests which are used for, identifying particular drugs., 4.Microchemical tests: These are the tests which are carried on slides., Example: Euginol in clove oil is precipitated as potassium euginate, , crystals.

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6.Biological Evaluation, , > It is employed when the drug cannot be evaluated satisfactorily, by chemical and physical methods., , > In this method, the response produced by the test drug on a, living system is compared with that of the stranded, preparation., , > Such an activity is represented in units as International Units, (1.U).Dose is termed as International units IU, , * Digitalis 11U=76mg of standard, , * Vit-A 11U=0.344 of standard, « Vit-D 11U=0.025of standard

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Indication of Biological Evaluation, When the chemical nature of the drug is not known but is has, an biological action., When chemical methods are not available., , When the quantity of the drug is small and so it cannot be, , evaluated chemically., , Drugs which have different chemical composition but same, , biological activity., Example: Cardiac glycosides arte evaluated by this method on, , cats, frogs or pigeons.

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SIGNIFICANCE, 1.The method is generally used when standardization is not done, satisfactory by chemical or physical methods, 2.When the quantity of the drug /sample are very less then the, drugs are evaluated by biological methods., 3.These methods are performed on living animals, isolating living, , organ and tissue, animal preparation, and micro-organism (, , Bioassay)