Ion-Mobility Spectrometric Determination of Hydrazines

Hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine can be detected and measured at concentrations as low as 10 parts per billion in the presence of ammonia at concentrations as high as 10 parts per million (greater than the odor threshold concentration of ammonia, approximately 5 ppm) by modified use of a portable, commercially available ion-mobility spectrometer. The modification consists in the substitution of 5-nonanone for acetone as the ion-forming compound in the drift or source region of the ion-mobility spectrometer. Previously, when acetone was used and ammonia was present in the sampled atmosphere even at ppm levels, chemical reactions between the ammonia and the acetone formed ion adducts that had mobilities comparable to those of monomethylhydrazine and that, consequently, interfered with the detection of hydrazines.