Ammonium purpurate

Murexide test. Place about o-i g. of uric acid in a small evaporating-basin and moisten with 2 3 drops of cone. HNO3. Heat very gently to dryness, and then add i drop of aqueous NHj from a glass rod a purple coloration is produced due to the formation of ammonium purpurate or murexide. Now add a drop of NaOH solution the coloration changes to blue. 

Interaction with murexide. The murexide method depends on the formation of a complex between Ca2+ and ammonium purpurate (murexide, M) ... 

The acceptor stream in this instance is limited to distilled water. The actual color development occurs after the alkaline buffer is premixed with the ammonium purpurate indicator and the resultant stream is admitted to the test solution. Since the pH at which color development is recorded is quite critical, the alkaline buffer used is the water soluble organic base, diethylamine, which has been adjusted to a pH of 11.7. 

Wl. Williams, M. B., and Moser, J. H., Colorimetric determination of calcium with ammonium purpurate. Anal. Chem. 26, 1414-1417 (1953). 

Murexide (ammonium purpurate) [3051-09-0] M 284.2, m >300 , S Onm (e 12,000), pKz 9.2, pKa 10.9. The sample may be grossly contaminated with uramil, alloxanthine, etc. Difficult to purify. It is better to synthesise it from pure alloxanthine [Davidson /i4m Chem Soc 58 1821 1936], Crystd from water. 

Various organic reagents are used for direct determination of calcium, such as murexide (ammonium purpurate) (e = 1.4-10 at 500 nm) [2,49], Metalphthalein [50], Calcein [51,52], Chrome Azurol S (in the presence of 1,10-phenanthroline) [53], Alizarin S [54], 8-hydroxyquinoline (extraction into CHCI3 in the presence of n-butylamine or butoxyethanol) [55], and Emodine (l,3,8-trihydroxy-6-methylanthraquinone) [56]. Calcium has been determined as a complex with Emodine, in the presence of Be and Mg, by the derivative spectrophotometry technique. The anionic complexes of calcium with bromo-oxine [57] or HTTA [58] have been extracted into benzene as ion associates with Rhodamine B. Calcium was also determined as a complex with o-cresolphthalein [59-63], or thymolphthalein [64]. 

Ammonium Purpurate (Murexide) Pink to purple Redox 0.5 g in 100 g K2SO4... 

Ammonium purpurate Ammonium salt purpuric acid Ammonium 5-(2,4,6-trioxoperhydropyrimidin-5-ylidene-amino)barbiturate ... 

Murexid—Ammonium purpurate — CeHiiNHANiOa — is produced by oxidation of uric acid, of alloxan, and of a number of other derivatives of uric acid with subsequent contact of ammonium hydroxid. It is supposed to be the ammonium salt of a hypothetical and non-isolated acid. The ammonium salt is of a brilliant, but evanescent purple color. (See p. 350.)... 

The method used involves the fast complexation reaction between transition metal ions Me + [Ni(II), Co(II), Zn(II)] and murexide (ammonium purpurate or Mu ).This reaction in an aqueous medium can be schematically represented by... 

Metal-ion-chelating agents ammonium purpurate a.ot -dipyridyl desferrioxamine B diethylenetriaminopentaacetic acid 2,3-dimercapto-l-propanol 4,5-dihydroxybenzene-l,3-disulphonic acid ethylenediaminetetraacetic acid (EDTA)... 

A test which is used for the detection of uric acid in calculi. It is based on the reaction of uric acid with nitric acid, followed by the addition of ammonium hydroxide to give ammonium purpurate which is coloured purple. 

Spec A = 555 nm of the binary complex sensitized with Triton X-100 (pH = 9.0) Spec determination of lanthanum with ammonium purpurate as a chromogenic reagent... 

Spec determination of scandium with ammonium purpurate as a chromogenic reagent... 

Murexide Ammonium purpurate 5,5 - nitrilodibarbitiuric acid monoammon-ium salt 1776 1818 (1853-1865) Cl 56085 Scheele (1742-1786) W Prout (1785-1850) Uric acid treated with nitric acid and ammonia... 

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