in nonhydrolysed urine , monoacetylated hda ( n-acetyl-1,6-hexamethylene diamine ) and hda , were verified as heptafluorobutyric anhydride derivatives by gas chromatography-mass spectrometry ( gc-ms ) , in a chemical ionization mode using isobutane and ammonia as reagent gases .
C0002607
ammonia
C0017110
gases