| 摘要 |
<p>A monitor that photo-ionizes trace constituents within a quadrupole ion trap (QIT). The QIT (102) may have a valve (116) that discharges a gas specimen into a trap chamber (106) or a gas line (216) that continuously discharges a gas specimen into the QIT. The trap chamber is surrounded by a ring (104), and an extractor plate (108) that has an orifice (112). The trace molecules within the air may be ionized at the nozzle of the valve by a photo-ionizer (120). Photo-ionizing at the valve nozzle provides a relatively high density of ionized molecules. The photo-ionizer may be either a pulsed light source or a continuous wave light source. The trace molecules are preferably ionized with energy between 8.0 and 11.0 electron volts (eV). The energy is selected to ionize the trace molecules without fragmenting the trace constituents. A radio frequency or other oscillating frequency voltage potential is applied to the ring to trap the ionized trace molecules within the trap chamber. A voltage pulse is applied to the extractor plate to pull the ionized molecules out of the chamber and through the orifice. The extracted ionized molecules are then accelerated (126) to a detector (130). The monitor has a time of flight analyzer (100) to measure the mass of the trace constituents in the specimen.</p> |
