testing presence of impurity at below 100 PPB levels

[maker50]

I have a sample of a HFC (hydrofluorocarbon) refrigerant and need to get it tested to see if it contains a particular impurity. However the two problems are that the levels of the impurity we are talking about are below the 100 PPB (0.1PPM) level, and also the sample does contain other impurities of the same molecular weight as what we are trying to test for, so need to be able to differentiate between them.

I have called several labs but no one seems to be able to test down to these levels.

Anyone know of any labs who can help?

[maker50]

I called some places and they told me I need to find a lab who can test using, electrospray mass spectrometry or negative chemical ionization. Does this make sense to anyone?

Also I called agilent and they told me the two pieces of equipment they make that can perform the test we are looking for are their MS 5975, and their g7000 triple quad or g7000 qqq. Anyone familiar with either of these pieces of equipment?

The impurity we are looking to test for is PFIB http://en.wikipedia.org/wiki/Perfluoroisobutene , it is some nasty stuff, with the problem being that the acceptable levels are so low 0.1ppm. http://www.osha.gov/dts/chemicalsamplin ... 60750.html

But I cannot find any government reports or testing procedures to follow. I think if this can be found then it will make everything much easier.

Though we do not think the sample contains any pfib, we need to be able to find a lab who can definitively test down to these levels and come back and say either that the sample does not contain any trace of pfib, or that it does contain and what the levels it contains are .

Of course to make things more difficult the molecular weight of the pfib is rather common, 4 carbon 8 fluorine. The HFC (sample) manufacturer has verified that they know their product contains other c4f8 molecules (impurities), but all the rest of these are rather safe, one (c318) even being a food spray and refrigerant used in nuclear facilities!

So the testing also needs to be able differentiate between the pfib and the many other c4f8 molecules.

Any help and/or suggestions about any of this, from the equipment, to test method, to recommended lab would be a great help and much appreciated. The lab would receive quite a significant amount of repeat business as this is going to be a highly tested for impurity in the near future, not just from us but from many other companies in the industry, some of them needing testing on a per batch basis.

[bhuvfe]

maker50,

I don't do gasses but a GC-MS with a sample loop or a GC-ECD should be able to help you out.

If you google your target they seem to refer to EPA method 5021.

Good luck.
bhuvfe

[maker50]

maker50,

I don't do gasses but a GC-MS with a sample loop or a GC-ECD should be able to help you out.

If you google your target they seem to refer to EPA method 5021.

Good luck.
bhuvfe

Thanks for the response and information on the gc-ecd. I did see the EPA 5021, but problem is that is for testing soil samples, and we are testing a gaseous refrigerant.

[maker50]

I found this link on nist site that might be of help in testing http://webbook.nist.gov/cgi/cbook.cgi?I ... L&Mask=608

Is that link of any use?

[bhuvfe]

maker50,

I don't do gasses but a GC-MS with a sample loop or a GC-ECD should be able to help you out.

If you google your target they seem to refer to EPA method 5021.

Good luck.
bhuvfe

Thanks for the response and information on the gc-ecd. I did see the EPA 5021, but problem is that is for testing soil samples, and we are testing a gaseous refrigerant.

The method uses headspace. The chromatographic separation you get will not change (normally..) You will simply need a sample loop for your refrigerant sample instead of a syringe.

[JI2002]

Maker50,

Which Freon is the refrigerant? Freon 113,12, 22, 114?
We can test VOCs in air samples by TO15 down to 5 pptV or lower, but because the matrix is a Freon, things are a little bit different and more complicated. If there are potentially many samples to the lab in the future, I like to take the challenge and give it a try if you can pay the cost of the gas standard.