The direct determination of creatine in pathological urine / by G.S. Walpole.

  • Walpole, George Stanley.
Date:
[1911?]
Catalogue details

Licence: Public Domain Mark

Credit: The direct determination of creatine in pathological urine / by G.S. Walpole. Source: Wellcome Collection.

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    to the creatine-diacetyl reaction were less when the creatine was contained in urine than when it was contained in water. This is apparently due to two causes. The presence of ammonium salts interferes with the reaction, and experiments were made in which the free ammonia in the urines examined was determined by Folin’s method1. Corresponding amounts of ammonia were added to some determinations of creatine in water, using, as usual, 2 c.c. of saturated sodium carbonate solution, diacetyl and water to 6 c.c. It was found in each case that the colour obtained was materially diminished by the ammonia added. To a number of samples of normal urine giving no indication, by this method, that creatine was present, known amounts of creatine were added. They were compared one with another by the method given, and it was found roughly that those with the highest free ammonia content gave the least increase of colour with diacetyl and alkali under standard conditions, and vice-versa. The accord was not perfect, and this led me to seek for the disturbing factor. From some normal urine phosphates were removed by baryta, and free ammonia by adding sodium carbonate and the passing air for some hours2. It was found that creatine added to the resulting solution still gave slightly less colour than it did in water. The second substance having the same effect as free ammonia is, together with urinary pigment, removed from urine by animal charcoal. It is not extracted by ether, and in this respect differs from the substance recently found in urine by Buckmaster3, which inhibits the pseudo-peroxydase reaction for blood. Removal of albumen. Protein gives the pink colour with diacetyl and alkali. To remove it I found trichloracetic acid satisfactor}7. It does not effect the reaction except in so far as it neutralises the sodium carbonate present. It should be added equally, of course, to all the tubes to which diacetyl is added. Comparison of results obtained by the Folin method and the diacetyl method above described. The method universally adopted is that of Folin4, in which the total creatinine before and after acid hydrolysis is estimated by the technique elaborated by him. Although this pro¬ cedure postulates several debateable points, and is a determination involving the small difference of two measured quantities, it proves in practice to be satisfactory. The original method described by Folin 1 Folin. Ztsch.f. Physiol. Chem. xli. p. 223. 1904. 2 Matthew Steel. Journ. Biol. Chevi. viii. p. 365. 1910. 3 Buckmaster. Proc. Physiol. Soc. p. xi. 1908 (This Journ. xxxvii.). 4 loc. cit.