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Detector Systems
Nitrogen-phosphorus detector (NPD)
129
Nitrogen-phosphorus detector (NPD)
NPD Collector
Assembly
Air Inlet
H
2
Inlet
NPD Collector
Active Element
Jet
Nitrogen-Phosphorus Detector (NPD)
Figure 7-3
The nitrogen•phosphorusdetector uses a jet and collector similar to the
FID; however, the collector contains a small alumina cylinder coated with
a rubidium salt (the active element) which is heated electrically. In the
presence of this thermionic source, nitrogen•and phosphorus•containing
organic molecules are efficiently ionized. Ions are collected, and the
resulting current is measured.