Guanidinoacetic Acid is an important marker for renal failure, in kidney transplantation, and for the renal metabolic activity.
Recrystallise it from 15 parts of hot H2O, or by dissolving it in slightly more than the calculated amount of 2N HCl and precipitating it by adding an equivalent of 2N NaOH, filtering, washing with cold H2O and drying first in vacuo, then at 60o in vacuo. The hydrochloride has m 200o(dec) after recrystallisation from aqueous HCl as plates. The picrate forms needles from hot H2O with m 210o(dec). [Brand & Brand Org Synth Coll Vol III 440 1955, Failey & Brand J Biol Chem 102 768 1933, King J Chem Soc 2375 1930, Beilstein 4 H 359, 4 I 477, 4 II 793, 4 III 1165.]
