4307
Conjugated and unconjugated phenylacetic acid and m - and p - hydroxyphenylacetic acid have been determined in the plasma of normal , healthy subjects after fasting , consumption of a meal and ingestion of deuterium labelled amine precursors , by high - resolution gas chromatography - - high resolution mass spectrometry with selected ion monitoring of their trifluoroethyl - pentafluoropropionyl derivatives .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 None