STABILITY 



phase. This is the basis of Peters' formaldehyde-azo test (see page 

 37). When a slightly alkaline solution of aneurine is treated with 

 potassiam ferricyanide solution, thiochrome is formed and the solution 

 acquires a blue fluorescence extractable into isobutyl alcohol. This 

 reaction also forms the basis of a method of estimating aneurine (see 

 page 38). 



Aneurine hydrochloride was included in the Third Addendum 

 (1941) to the British Pharmacopoeia 1932, which laid down tests for 

 identity and purity. Each gram contains 320,000 international units. 

 The monograph was slightly modified in the Seventh Addendum 

 (1945), and revised in the British Pharmacopoeia, 1948. The prophy- 

 lactic and therapeutic doses are given as i to 3 mg. and 10 to 30 mg. 

 daily respectively. Injection of aneurine and tablets of aneurine were 

 made official in 1948. 



References to Section 5 



1. J. D. Bernal and D. Crowfoot, Nature, 1933, ISl, 911. 



2. Armour Research Foundation, Anal. Chem., 1948, 20, 683. 



6. STABILITY OF ANEURINE 



Aneurine hydrochloride is stable in the dry state, and acid solu- 

 tions can be stored for some time without loss of activity. It is 

 unstable in neutral or alkaline solution, however, especially when 

 exposed to air. Gastric juice, which is of course acid, has little or no. 

 effect on aneurine, but when antacids have been used, some destruc- 

 tion may occur.^ Gastric juice from patients with achlorhydria did 

 not cause destruction, but bile and duodenal pancreatic juice, which 

 are slightly alkaline, rapidly destroyed aneurine. 



According to K. T. H. Farrer ^ aneurine is completely destroyed in 

 fifteen minutes at 100° C. at ^H 9, whilst at pH 8, 7, 6, 5, 4, and 3, the 

 proportions destroyed within one hour are 100, 67-8, 53-4, 40-0, 20-3 

 and i6-o % respectively and within three hours 100, 96-4, 86-3, 67-^, 

 44-5, and 29-1 % respectively. No loss of activity occurred in i % 

 hydrochloric acid solution in seven hours. The stability is not solely 

 determined by the ^H of the solution, however, but depends on the 

 nature of the buffer employed, for Beadle et al.^ showed that on heating 

 a solution of aneurine of pK 5-4 for one hour at 100° C, 100 % destruc- 

 tion occurred with a borate buffer, 10 % with an acetate buffer, 3 % 

 with a phosphate buffer and 57 % in an unbuffered solution. In 

 general, the destruction increased as the pH increased. The protective 

 action of the phosphate buffer was confirmed by R. G. Booth,* who 

 showed that less vitamin was lost in phosphate buffer than in phthalate 



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