TheSRINitrogen-PhosphorusDetector (NPD)hasa
linearresponseselective toorganiccompoundscontaining
nitrogenand/or phosphorus.TheNPDalso responds to
normalhydrocarbons,butapproximately100,000timesless
thannitrogenorphosphoruscontainingcompounds.Dueto
itsselectivityandsensitivity,theNPDisoftenusedtodetect
pesticides, herbicides, drugs of abuse, and other trace
compounds.Nitrogen is thecarriergasofchoice for the
NPDdetector,buthelium isoftenused, especiallywhen
otherdetectorsare installedon thesameGCas theNPD.
Overview
TheNPDmaybecombinedwiththeDELCDforpesticide
screening.TheNPDdetectsOrgano-phosphatepesticides
and theDELCDdetects thechlorinatedpesticides.
TheNPD issimilar indesign to theFID, except itusesa
thermionicNPDbead togenerate ions inahydrogenand
airplasma.Like theFID, theNPDusesastainlesssteel jet todeliversample-ladencarriergasandhydrogen
gas to thedetector,andapositivelychargedcollectorelectrode thatalsoservesas thedetectorexhaust.The
NPDbead ispositionedbetween the jetand thecollectorelectrode.The tipof theNPD jet isslightlydifferent
from thatof theFID jet.
The thermionicNPDbead is
coatedwithanalkali salt.
TheNPD issimilar to theFID indesign.
DETECTORS
Nitrogen/Phophorus Detector - NPD
