53
GCDetectors
FPD - FlamePhotometricDetector
FPD, Dual FPD, FPD/FID, FID/Dual FPD
• BandpassFilters for Sulfur or Phosphorus
• Use theDual FPD for SimultaneousSulfur andPhosphorus
Detection
• DetectsSulfurCompounds to 200ppb, PhosphorusCompounds
down to10ppb
• Use theFPD/FIDorDual FPD/FID for SimultaneousHydrocarbon
Speciation
The Flame Photometric Detector can detect sulfur compounds, such as
H
2
Sor SO
2
, down toabout 200ppbandphosphoruscompounds to10ppb.
While not 100% selective, the FPD is 100,000 times more sensitive to
sulfur and phosphorus compounds than hydrocarbons. The phosphorus
response is linear, and the sulfur response is exponential (twice the sulfur
yields four times thepeak area).
The FPD is similar to the FID except that the detector body is light tight and a second low of hydrogen
purges the optical path between the photomultiplier tube (PMT) and the hydrogen rich lame. A bandpass
ilter (at 393nm for sulfur and525nm for phosphorus)mounts in front of thePMT, soonly theemissions from
sulfur or phosphorusaredetectedwhileotherwavelengthsare rejected. TheDual FPDdetector isequipped
with twoPMTs and ilters for the simultaneous detectionof sulfur andphosphorus.
The twochromatogramsshownat rightwereproducedbyanSRI
GCequippedwithanFPDdetector.The topchromatogramshows
the FPD response to 10ppm H
2
S. The bottom chromatogram
shows the FPD response to 10ppm malathion, a pesticide
containingboth sulfur andphosphorus.
10ppm
malathion
sample
10ppmH
2
S
sample
