Several instruments have been developed to measure low concentrations of hydrazine but none are completely satisfactory. A brief review is presented of current instruments such as the electrochemical cell, the ion mobility spectrometer, the mass spectrometer, the gas chromatograph, and the electronic nose.

Hydrazine (HZ) and monomethylhydrazine (MMH) in air were monitored continuously using a hand-held ion mobility spectrometer equipped with membrane inlet, ssNi ion source, acetone reagent gas, and ambient temperature drift tube. Response characteristics included detection limit, 6 ppb; linear range, 10-600 ppb; saturated response, >2 ppmj and stable response after 15-30 min. Ammonia interfered in hydrazines detection through a product ion with the same drift time as that for MMH and HZ. Acetone reagent gas was replaced with 5-nonanone to alter drift times of product ions and separate ammonia from MMH and HZ. Patterns in mobility spectra, ion identifications from mass spectra, and fragmentation cross-sections from collisional-induced dissociations suggest that drift times are governed by ioncluster equilibria in the drift region of the mobility spectrometer. Practical aspects including calibration, stability, and reproducibility are reported from the use of a hand-held mobility spectrometer on the space shuttle Atlantisduring mission STS- 37.

The development of hand-held, ambient-temperature instruments that utilize ion mobility spectrometry (IMS) in the detection of hydrazine and monomethylhydrazine is reviewed. A development effort to eliminate ammonia interference through altering the ionization chemistry, based on adding 5-nonanone as dopant in the ionization region of the IMS, is presented. Calibration of this instrument conducted before and after STS-37 revealed no more than a 5 percent difference between calibration curves, without any appreciable loss of equipment function.