In thecombomode, theDELCD isoperatedafter theFID. TheFIDsignal isusuallyconnected toChannel1
on thePeakSimpledatasystem. TheDELCDsignalmaybeonChannel2or3. Eachdetectoramplifier is
labeledatthefactorywiththedatachanneltowhichithasbeenconnected. Detectorsignalsmaybeconnected
toanyavailabledatachannelbysimplyattachingthewhiteandblacksignalwirestothescrewterminalsonthe
A/Dboard inside theGC.
1) Set theFIDhydrogenandair flows fornormalFIDoperation. This is typically25ml/minhydrogen
(corresponds to25psi)and250ml/minair(typically6psi). Theexactpressurerequiredforeachflow is
labeledon theGC’srighthandside.
2) Set theDELCD temperaturesetpoint to260using the frontpaneladjustments. Thisnumberactually
represents1000ºC. TheDELCDwillheatup toabout254andstabilize. Thequartzcollectorelectrode
willappearabright redcolordue to the1000C temperature.
3) In theFID/DELCDcombomode, theFID isnormallyoperatedonhighgainoronhi-filteredgain if the
peaksaremore than10secondwideat thebase. Thehi-filteredgainposition is identical to thehighgain
exceptthatextranoisefilteringresultsinaquieterbaseline. TheDELCDamplifierisnormallyoperatedon
lowgain. InthisconfigurationtheFIDandDELCDproduceapproximatelythesameresponsetochlorinated
peakssuchasTCE (samepeakareacounts ). TheFIDwillgenerateapproximately4areacountsper
nanograminjectedoncolumnwhiletheDELCDwillgenerate2-4areacountspernanogramofchlorinated
hydrocarbon. (seeexamplechromatogrambelow).
Operating the FID/DELCD in the Combo mode
DETECTORS
FID/DELCD
TheFIDshows500areacounts for100nanogramsofPerchlorethylene (PCE)
TheDELCDshows250areacounts for100nanogramsofPerchlorethylene (PCE)
