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The
Nitrogen Phosphorus Detector ( NPD ) is similar in design to the FID, except
that the hydrogen flow rate is reduced to about 3 ml/min and an electrically
heated thermionic bead ( NPD bead ) is
positioned near
the jet orifice. Nitrogen or phosphorus containing molecules exiting
the column
collide with
the hot bead and undergo a catalytic surface chemistry reaction.
The ions created in this reaction are attracted to a collector electrode,
amplified, and output to the data system. The NPD is commonly used
to detect pesticides, herbicides, and drugs of abuse because it responds
to N-P compounds about 100,000 stronger than normal hydrocarbons, making
it very selective. When
combined with
the chlorine/bromine selective DELCD, the combined detector is ideal for
pesticide screening since the NPD selectively detects the organo-phosphate
pesticides, while the DELCD
detects only
the chlorinated species. Together all pesticides can be detected,
and the relative
responses can
help to identify pesticide species. The SRI ceramic NPD bead is exceptionally
rugged and long-lasting, offering service from 100-1000 hours depending
on operating conditions.
8690-0015 Nitrogen-Phosphorus detector
( NPD )
Includes: one NPD bead
$2,995.00
8690-2615 NPD/DELCD combination detector
Includes: one NPD bead and
two DELCD
detector assemblies
$5,995.00 |
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