Anal. Chem. 1991, 63, 1755-1759
1755
Modulated Photoionization Detection of Hydrazine Compounds in Mixtures without Prior Separation Joseph R. Stetter,* Chen-Xi Shi,’ and G. Jordan Maclay Transducer Research, Inc., 999 Chicago Avenue, Naperville, Illinois 60540
Two modulated photoionizatbndetector (PID) methods have been developed to detect hydrazlne compounds seiectlvely derpne potenthi Interference caused by the presence of hydrocarbons, NH,, Freon, and CO. Wlth approprlate slgnal modulation, the PID can both klentlty and quantlfy hydrazlne compounds wlth exceptlonai selectivlty, even in mlxtures. One modulatlon technique Is based on the different decomposltlon ratios of the chemlcal compounds at different temperatures of a platinum filament, dtuated at the PID sample Inlet and controlled In ON/OFF modes by an electric power switch. I n the second modulation technique, the platinum fhnenl Is replaced by an acetk anhyarclelitter at the sample Inlet, and the chemkal fitter Is switched “In” and “out” of the flow path by a three-way solenoid valve. I n the first case, dgnlflcantly different responses of hydrazine compounds at ON and OFF filament condltlons enables quantltatlve determination of methylhydrazlne (MMH) to a detectlon llmlt of
