TIME PERSISTENCE OF MONOCHLORAMINE IN HUMAN SALIVA AND STOMACH FLUID

On-line membrane introduction mass spectrometry has been used to analyze the time persistence of monochloramine in human saliva and stomach fluid. The decay of monochloramine from a level of 0.7 ppm to levels below the detection limit (100 ppb) in saliva takes approximately 5 min; from a level of 1.8 ppm the decay time is approximately 50 min and at higher monochloramine concentrations (3.6-15 ppm) monochloramine does not react completely. This result, together with the short residence time of water in the mouth, suggests that most ingested monochloramine reaches the stomach intact. In contrast to its reaction with saliva, monochloramine decays rapidly in contact with stomach fluid; at concentrations of 0.7-15 ppm this occurs in approximately 30 s. This study also shows clearly the advantages of membrane introduction mass spectrometry in chloramine analysis. The ability to analyze these toxic and labile compounds directly from aqueous samples without derivatization or isolation at low detection limits is a prerequisite for establishing the biological fate of these compounds.