Waters Xevo TQD, Operator'S, Overview And Maintenance Manual, Page: 61 / 250

Combined APPI/APCI source 3-9
4. Unscrew the probe locking ring.
5. Carefully remove the probe from the probe adjuster assembly.
Combined APPI/APCI source
Operate this optional, replacement source enclosure in APPI, APCI, or dual
APPI/APCI mode. Dual-mode APPI/APCI performs rapid switching between
ionization modes.
APPI operation
In atmospheric pressure photoionization (APPI) mode, the source is fitted
with an IonSABRE II probe and the APPI lamp drive assembly is advanced
into the source.
APPI mode:
The IonSABRE II probe introduces vaporized sample into the source where
photons generated by an ultraviolet (UV) lamp (mounted in the APPI lamp
drive assembly) produce sample ions. Direct photoionization of a sample
molecule occurs when the photon energy exceeds the ionization potential of
the sample molecule.
A repeller electrode (mounted on the APPI lamp drive assembly) deflects and
focuses the sample ions toward the sample cone.
IonSABRE II probe
Sample molecules
APPI lamp drive assembly
Repeller electrode UV lamp
Sample ions
Sample cone
Photons from
the UV lamp