Analysis of ppb Levels of Low MW Organics Compounds Using an 11.7 PID-GC

The ionization potential (IP) of low molecular weight saturated organic compounds are > 10.6 eV but < 11.7 eV. This group of compounds (ethane-butane), chloroalkanes (CH3CL. CHCl3, CCl4, CH2CL2, C2H4Cl2 etc.), oxygenates (methanol & formaldehyde) are difficult to do with any single detector except the PID with an 11.7 lamp. The dynamic range of the PID with an 11.7 eV lamp is about 106 with detection limits in the 50-100 ppb range. These detection limits could be improved using thick film capillary columns. A comparison of the range of the 11.7 eV lamp with other GC detectors is shown below.

The response of low MW alkanes C2-C6 for the PID 11.7 is shown in the chromatograph below:
C2-C6 HC with the PID 11.7

Note that the PID 10.6 eV will only respond to C5 & C6 alkanes.
The chromatogram below via PID 117 detects some chlorinated HC including ethylene dichloride (C2H4Cl4). (IP= 11 eV). Of course, the PID 11.7 also detects low ppm levels of MeOH and chloroform as shown below. Note the high sensitivity of the low MW chlorinated hydrocarbon.

The PID 11.7 also has a high sensitivity to formaldehyde, one of the few detectors that respond to formaldehyde at ppb levels without the need for derivitization. A chromatogram of methanol and formaldehyde is given below.

Can I still get my old HNU PI101 fixed?

That was a common question at the AICHE (#AIHA) show in Portland, OR (May 14-20, 2010). We, PID Analyzers, LLC, brought one of the first PI101's (1st portable photoionization analyzer) ever built to the show. I had many people who stopped, looked at the PI101 and said "I used one many years ago but I didn't realize  that you still made them". I said that we stopped making them about ten years ago but we can still fix them,  Several people asked about an 11.7 probe for their 101 and I said "we can still supply one". I even had one industrial hygienist who stopped by who said " I bought my PI101 25 years ago and it still works. I said "you should send it in for a clean and cal, it will probably need one after 25 years".

Some of our competitors build their PID's like cell phones. That is, their lifetime is just over 2 years and spare parts are available only for several years beyond that. We can fix PI101's that were built 35 years ago. The PI101 was the first portable analyzer that was used extensively in reducing exposure to vinyl chloride, solving exposure problems at Love Canal (1st Superfund Site) and written in to the Superfind legislation. Note that Superfund was "the world's largest industrial hygiene program". That is all history now but the PI101 is still around and can still be fixed 35 years later. For more information click here. 

A photo of the PI101 with its successor, the Model DL102, is shown in the photo below:   

                                                                    Model PI101

Multisensor 102+