50
GCDetectors
PID - Photo IonizationDetector
• Responds tomoleculeswithcarbondouble
bonds andaromatics
• Sensitive (down to10ppb) and
nondestructive
• Mandated in several EPAMethods
• Extremely long lamp life!
This PIDchromatogramshows a separationof a
100ppmBTEXplus sample using a 0.53, 15meter
capillary column andheliumcarrier gas.
Use of the Photo IonizationDetector ismandated in
several EPA methods (8021, TO-14, etc.) because
of its sensitivity and selectivity. Detection limits
for aromatics are in the low picogram (ppb) range.
Because it is nondestructive, the PID is often run in
serieswithotherdetectors—typically theFID/DELCD
combination detector—for multiple chromatograms
from a single injection.ThePID is also able to run on
air carrier,whichcanbeuseful insituationswhereno
gas isavailable,or forstreammonitoringapplications
where no column is used to separate compounds.
UnlikeotherPIDdesigns, the lampon theSRIPIDcanbeeasily removed,without tools, forperiodiccleaning
of the lampwindow toavoid interference fromcolumnbleedbuild-up. Lamps can last yearson theSRI PID
because only the lampwindow is heated, not the entirebody of the lamp.
The SRI design uses the
industry standard 10.6eV
PIDlampinaspring-loaded
mount, which allows the
lamptoberemoved, cleaned
and reinstalled in seconds
without tools.
The SRI PID consists of an industry standard UV lamp mounted on a thermostatted, low-volume, low-
through cell. The temperature is adjustable from ambient to 250°C. The 10.6 electron volt UV lamp emits
energy at awavelength of 120 nanometers, which is suficient to ionizemost aromatics (benzene, toluene,
xylene, etc.) andmany other molecules (H
2
S, hexane, ethanol) whose ionization potential is below 10.6eV.
Methanol andwater, for instance, have ionizationpotentialsgreater than10.6eVanddonot respondon the
PID.
8690-0040
PIDdetector
