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These notes, from
RAE
Systems, provide advice on using your PID.
Question: Can I measure
trichloroethylene with a standard 10.6 eV PID lamp?
Answer: Trichloroethylene (TCE) can be measured with a 10.6 eV or
even a 9.8 eV lamp, but chlorinated alkanes need an 11.7 eV lamp. Simple
chlorinated alkanes can't be detected with a 10.6 eV lamp. Compounds that
require an 11.7 eV lamp to measure include: methylene chloride (CH2Cl2),
chloroform (CHCl3), carbon tetrachloride (CCl4), 1,1,1-trichloroethane
(1,1,1-TCA) and 1,1,2,2-tetrachloroethane.
Compounds that CAN be detected with a standard 10.6 eV lamp include vinyl
chloride monomer (VCM), dichloroethylene (DCE),trichloroethylene (TCE),
perchloroethylene (PCE), and chlorobenzenes.
PIDs respond by functional group. Even though a standard 10.6 eV PID does
not respond to chlorine groups, other functional groups in the molecule,
such as double bonds, aromatic rings, and carbonyl groups can still give a
response. Sometimes the chlorines actually
enhance the response to such groups. For example, TCE (CF = 0.54) responds
much more strongly than ethylene itself (CF = 10). Chlorobenzene (CF =
0.40) and 1,2,4-trichlorobenzene (CF = 0.46) are slightly more sensitive
than benzene itself (CF = 0.53).
Response to halogenated compounds increases with halogen size:
• Fluorine generally makes sensitivity weaker and usually cannot be
detected.
• Chlorine compounds usually require a 10.6 eV or 11.7 eV lamp
• Bromine compounds are typically measured with a 10.6 eV lamp
• Iodine compounds are among the most sensitive compounds known, even with
a 9.8eV lamp!
For more information, please refer to RAE Technical Note TN-106
here. |
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