STABILITY OF ALLANTOIN AND IDENTIFICATION OF ITS DEGRADATION COMPOUNDS

The stability of allantoin was studied in pH 3.0, 6.0, and 8.0 buffer solutions at 50-degrees-C for 55 d. Allantoin was determined by high p erformance liquid chromatography (HPLC) with a cation exchange mode an d colorimetry. The known degradation compounds, allantoic acid and gly oxylic acid, were simultaneously determined by ion chromatography. Ure a was determined by HPLC with an ion pair mode. In the stability studi es on pH 6.0 and 8.0 solutions, new degradation compounds of allantoin were identified as two growing unknown peaks in the HPLC chromatogram . Isolation of these compounds by preparative HPLC and H-1, N-15 and C -13-NMR spectra revealed that they were condensates of allantoin and g lyoxylic acid, which also reacted positively in phenylhydrazine colori metry. The amounts of these compounds were calculated from the determi nation results of other allantoin related compounds in the buffer solu tions and were estimated as the biggest amount among all other compoun d. As they were found to be stable in an alkaline solution, conditions for hydrolysis in the colorimetric determination of allantoin were fu rther examined. It was found that the longer hydrolysis gave more than 90% recovery in the colorimetry.