| 摘要 |
<p>This invention provides methods and apparatus for determining the presence or absence of a specific constituent in a mixture. A thermal desorption unit (10) includes a body providing a desorption chamber, a removable end cap (14) for closing the chamber (18), a desorber heating system (19a, 19b) arranged to heat the desorption chamber (18), a gas inlet (17a, 22b) to the desorption chamber (18), and a gas outlet (24, 26) from the desorption chamber (18). A valve assembly (17b, 22a) can operate in a run mode to direct a carrier gas to the thermal desorption unit gas inlet (17a, 22b), and couple the thermal desorption unit gas outlet (24, 26) to an inlet of a sample analysis instrument. The valve assembly also can operate in a flush mode to direct the carrier gas to the inlet of the gas analysis instrument, direct a flushing gas to the thermal desorption unit gas inlet, and couple the thermal desorption unit gas outlet to an exhaust.</p> |
