The chemical evaluation includes qualitative chemical tests, quantitative chemical tests, chemical assays, and instrumental analysis. The isolation, purification, and identification of active constituents are chemical methods of evaluation. Qualitative chemical tests include identification tests for various phytoconstituents like alkaloids, glycosides, tannins, etc.
CHEMICAL EVALUATION
The chemical evaluation includes qualitative chemical tests,
quantitative chemical tests, chemical assays, and instrumen-tal analysis. The
isolation, purification, and identification of active constituents are chemical
methods of evaluation. Qualitative chemical tests include identification tests
for various phytoconstituents like alkaloids, glycosides, tannins, etc. The
procedures for the identification tests of various phytoconstituents are given
under their respective chapters in the text, where it could be referred.
Examples of identification of constituents are: copper acetate used in the
detection of colophony present as an adulterant for resins, balsams, and waxes;
Holphen’s test for cottonseed oil and Baudouin’s test for sesame oil in olive
oil; the test with acetic and nitric acids for Gurjun balsam in copaiba; Van
Urk’s reagent for ergot; Vitali’s morins reaction for tropane alkaloids; iodine
for starch; murexide test for purine bases, etc. are examples of this
evaluation.
Quantitative chemical tests such as acid value (resins,
balsams), saponification value (balsams), ester value (balsams, volatile oils),
acetyl value (volatile oils), etc. are also useful in evaluation of a drug by
means of chemical treatment.
Chemical assays include assays for alkaloid, resin, volatile
oil, glycoside, vitamins, or other constituent. Few examples are the assay of
total alkaloid in belladonna herb, the total alkaloid and nonphenolic alkaloid
in ipecacuanha, the alkaloid strychnine in nux vomica, the resin in jalap, and
the vitamins in cod-liver oil. The results obtained can conclude the presence
of inferior or exhausted drug and, by proving absence of the assayed
constituent, it will suggest complete substitution of a worthless article.
Instrumental analyses are used to analyse the chemical
groups of phytoconstituents using chromatographic and spectroscopic methods.
Chromatographic methods include paper chromatography, thin-layer
chromatography, gas chromatography, high-performance liquid chromatography,
and high-performance thin-layer chromatography. Spectroscopic methods include
ultraviolet and visible spectroscopy, infrared spectroscopy, mass spectroscopy,
and nuclear magnetic spectroscopy.
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