1) Asshown in thechromatogramabove, theDELCDpeak forPCEoccursat thesame timeas theFID
peakforPCE. Notice that theDELCDpeakexhibitsa littlebitof tailingcompared to theFIDresponse.
2) IntheFID/DELCDcombomode,theminimumdetectableamountisapproximately1nanogram. Assuming
a1microliter injection, this translates intoapproximately1ppm. Theexactdetection limitwilldependon
theanalytemolecule(howmuchchlorine/bromineinthecompound)andthechromatographicconditions.
Asharppeak isalwaysmoredetectable thanashort fatpeak.
3) Thedetectionlimitwillbeworsewhenusingthebuilt-inaircompressorforFID/DELCDflamecombustion
insteadofcleandry tankair. While thebuilt-inaircompressor isusefulandconvenient, low levelsof
halogenatedcompoundsintheambientair(evenlevelsbelow1ppm)causetheDELCDtolosesensitivity,
andfluctuations in the leveloforganics in theambientairmaycauseadditionalbaselinenoise.
4) In theFID/DELCDmode theDELCD response isuseable from1 to1000nanogramswithaslightly
quadraticcalibrationcurve. EPAandotherregulationsallowtheuseofdetectorswithnon-linearresponse
as longas theoperatorcalibrates
with sufficient data points to
accurately model the detector
responsecurve. Wherea5point
calibrationwould normally be
required, the DELCD may
demanda6pointcalibration.
Operating the FID/DELCD in the Combo mode
TheDELCDcalibrationcurveshownat
right illustrates thequadratic response
from1–1000nanogramsofTCE injected
DELCDpeakoverlaidonFIDpeak forPCE, thenexpanded forclarity. Thesmallerpeak is theDELCD response.
DETECTORS
FID/DELCD
