VOLATILE ORGANIC-COMPOUND ANALYSIS BY AN INERTIAL SPRAY EXTRACTION INTERFACE COUPLED TO AN ION-TRAP MASS-SPECTROMETER

A new interface has been developed for direct analysis of volatile org anic compounds (VOCs) from aqueous solutions without prior sample trea tment. The device consists of a nozzle directed vertically downward in a spray chamber, which is in turn coupled through a helium jet separa tor to an ion trap mass spectrometer. The nozzle reduces the liquid to an aerosol with the help of a helium carrier gas and rapid sample inj ection. The large surface area of the aerosol permits a rapid equilibr ation of the VOCs between the gas and liquid phases, The aerosol dropl ets impinge by their inertia on the floor of the spray chamber, where they coalesce for subsequent removal from the interface, The VOCs are carried from the interface by the helium flowing countercurrent to the spray, The combined VOC-helium mixture passes through a jet separator , which removes most of the carrier gas, and the concentrated VOCs are then analyzed by an ion trap mass spectrometer. This inertial spray e xtraction mass spectrometry method is very sensitive and has detection limits of < 1 ppb for most compounds analyzed (e.g., benzene is detec ted at 90 ppt). Using this system, we have analyzed halothane in blood from an anesthetized pig. Excellent correlations are obtained between this interface and conventional headspace gas chromatography for the analysis of toluene and xylene in blood from rats exposed to these com pounds and for spiked human blood.