DETERMINATION OF AMMONIA IN ETHYLENE USING ION MOBILITY SPECTROMETRY

A simple procedure to analyze ammonia in ethylene by ion mobility spec trometry is described. The spectrometer is operated with a silane poly mer membrane, Ni-63 ion source, H+(H2O)(n) reactant ion, and nitrogen drift and source gas. Ethylene containing parts per billion (ppb) (v/v ) concentrations of ammonia is pulled across the membrane and diffuses into the spectrometer. Preconcentration or preseparation is unnecessa ry, because the ethylene in the spectrometer has no noticeable effect on the analytical results. Ethylene does not polymerize in the radioac tive source. Ethylene's flammability is negated by the nitrogen inside the spectrometer. Response to ammonia concentrations between 200 ppb and 1.5 ppm is near linear, and a detection limit of 25 ppb is calcula ted. (C) 1997 Elsevier Science B.V.