Murexide test
The murexide test is an analytical technique to identify the presence of caffeine and other purine derivatives in a sample. These compounds do not respond to the common alkaloid identification tests such as Dragendorff's reagent. In this test, crude drugs (to be identified) are mixed with a tiny amount of potassium chlorate and a drop of hydrochloric acid. The sample is then evaporated to dryness and the resulting residue is exposed to ammonia vapour. Purine alkaloids produce a pinkish-purple color in this test[1][2] due to formation of murexide (ammonium purpurate; appears purple in pure state), which the test is named after.[3]
In pure form, murexide appears purple, but when it is produced by reaction of acidified solutions of purines and ammonia, various shades of purple and pink are produced.
Uses[edit]
Murexide test is a color test for uric acid and some other purines. The (solid) sample is first treated with small volume of a concentrated acid such as hydrochloric acid, nitric acid, which is slowly evaporated away; subsequent addition of ammonia (NH3) gives a purple color if uric acid was present, due to formation of murexide, or a yellow color that turns to red on heating if xanthine or its derivatives are present.
References[edit]
- ^ Agarwal O.P. Advanced Practical Organic Chemistry (26th ed.). Meerut, India: GOEL Publishing House. p. 53.
- ^ Nayeem AA, Khatun A, Rahman MS, Rahman M (2011). "Evaluation of phytochemical and pharmacological properties of Mikania cordata (Asteraceae) leaves". Journal of Pharmacognosy and Phytotherapy. 3 (8): 118–123.
- ^ Sharma DC; Sharma. Riyat. Practical Medical Biochemistry. BI Publications Pvt Ltd. p. 36.
