This paper describes the use of a PID Analyzers Model 102 photoionization analyzer with a long life 11.7 eV lamp to measure chlorinated HC including carbon tetrachloride.
Measurement of chlorinated HC with an 117 PID.pdf gasanalysis.blogspot.com
Measurement of chlorinated HC with an 117...
Still I wouldn't use a PID if I had more than one solvent as it would be extremely difficult to differentiate between them especially if one was a chlorinated hydrocarbon and the other was a non chlorinated solvent. A PID would be useful if you are doing a general survey to determine presence of solvents in an area were you already know qualitatively what exists in the matrix. But then an FID or an FPD would do the same job why use a PID ? A more difficult question is why would you want to do such a survey at all? I have used TO-17 or T0-15 for surveys for years and in my opinion the results much more accurate results albeit you have to wait for the laboratory analysis.
As I said in the beginning of this discussion if you must have immediate results I would use a portable GC-MS . Yes its heavier ,more expensive and difficult to use, but its also more accurate and the results coming from it definitely would stand up in court were as I sincerely doubt if results from a PID scanner would.
see http://www.epa.gov/ttnamti1/airtox.html#compendium for all the ambient methodology when you need to use a Mass spec otherwise http://www.osha.gov/dts/sltc/methods/organic/org007/org007.html or
http://www.cdc.gov/niosh/docs/2003-154/
Although we will never get one opinion in here ,maybe someone from NIOSH or OSHA is listening and could weigh in??
The main advantage of a PID is that it does respond to many compounds so one does not need a specific analyzer for every solvent that they use. The PID has a fast response (90% in 1 second) and can detect very low levels of VOC’s (ppb) so it can be used to find problem areas very quickly. Once an area is mapped, a charcoal tube sample is collected in the “hot” spots and returned to the laboratory for a detailed analysis of the chemicals in the area by various OSHA methods. In fact, the portable PID’s are used by OSHA to determine sampling locations during their surveys of industrial plants. With a PID to determine which problem areas to sample, one would have a more accurate assessment of the site.
I agree with you 100%.
The right tool in the right hand at the right time,
Thanks, this is the good kind of quality discussions we should have here.
Have a nice day
After living thirty years of Industrial Hygiene and Atmospheric Science you
must understand that I have heard many long tales of misuse of equipment
and then had to eat the dust myself. How many times have a heard people
trying to convince a Judge that they measured concentrations with whatever
handheld sensor and that a 3 second measurement was equivalent to a
measurement over 30 minute average period which was required by law???
This discussion started before I was born in 1955 with Leidel and Leidel
when people were trying to prove that you could simulate worker exposure by
setting up and number of sensors in a factory, measuring the time the
worker was in each area, integrating between time and exposure and hockus
pockus you get an exposure value which is supposed to represent reality.
Well in reality this method didn't work in 1955 and it doesn't work now
either.
Then again as you explained very clearly there are advantages to a
screening tool and it always comes down to the right tool in the right hand
at the right time.
Thanks for the opportunity to discuss a real hot potato and for handling it
in a very professional way.
Hope that we will have many more such discussions here.
Best Regards
Gershon Schwartz
sentex weighed over 20 kg and gave me a slipped disc. Then there was the
Photovav gc pid which wasn't very stable in the field. Does anybody know if
there are any portable gc's available today? Seems to me like another great
idea on paper that never worked in the field?
Best regards
Let me check what I can find for your blog.
If you need a good field instrument or something accurate but portable, I'd recommend the Miran SapphIRe - it uses infrared spectroscopy and the XL model has a comprehensive library that calibrates the unit to 150 compounds for unknown identifications and can be customized for whatever you are looking for. (Here's the spec sheet)
It's a whopper to carry around but very helpful in instances where we needed to know the actual concentrations (or as nearly as we could get). The Miran is cheaper than a portable GC-MS (costs around $25K to buy), but with all these detectors, you can rent them from folks like Ashtead or Geotech for a reasonable fee... Lastly, as Gershon mentioned above, TO-15 or TO-17 canister sampling can be done, and if you are in a hurry, there are mobile labs that can do these analyses on-site (such as H&P Mobile Geochemistry and Con-Test) using Tedlar bags and/or Summa canisters.