[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 performance liquid chromatography (HPLC) with a cation exchange mode and colorimetry. The known degradation compounds, allantoic acid and glyoxylic acid, were simultaneously determined by ion chromatography. Urea was determined by HPLC with an ion pair mode. In the stability studies 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 1H, 15N and 13C-NMR spectra revealed that they were condensates of allantoin and glyoxylic acid, which also reacted positively in phenylhydrazine colorimetry. The amounts of these compounds were calculated from the determination results of other allantoin related compounds in the buffer solutions and were estimated as the biggest amount among all other compound. As they were found to be stable in an alkaline solution, conditions for hydrolysis in the colorimetric determination of allantoin were further examined. It was found that the longer hydrolysis gave more than 90% recovery in the colorimetry.
Yamamoto
S
S
Analytical Research Group, Shiseido Research and Development Headquarters, Yokohama, Japan.
Ohtomo
M
M
Komatsu
K
K
Takamatsu
T
T
Matsuoka
M
M
D000481:Allantoin / Q000032:analysis*; D002021:Buffers; D002851:Chromatography, High Pressure Liquid; D003124:Colorimetry; D004355:Drug Stability; D006038:Glyoxylates / Q000032:analysis; D006863:Hydrogen-Ion Concentration
D002021:Buffers; D006038:Glyoxylates; D000481:Allantoin; C031150:glyoxylic acid