1-4 Dioxane Purge and trap

[msbonner]

The EPA Volatile Organics Method for (CLP) laboratories includes 1-4 Dioxane as one of the analytes. This compound does not purge well under the conditions that work best all the other analytes. EPA requires a response factor of 0.006 we have not been able to routinely achieve an 0.006 RF and at the same time have the gaseous compounds pass the method criteria. We can increase the purge temperature and add a dry purge to get dioxane to pass but we then lose the gaseous compounds. Has anyone solved this problem?
Thanks

[carl.nott]

I've run 1,4-Dioxane at a non-CLP lab. We did not use Purge and Trap as we ran into the same issues you were having. We had a 5971 GC/MS + FID that was set up for clients who requested Gx+BTEX by 8260 (how exactly Chemstation was set up for this configuration escapes me). We also used it for analysis of 1,4-Dioxane by adding a 7673 autosampler and performing an isotopic extraction of 1,4-Dioxane with 1,4-Dioxane-d8 in methylene chloride with direct injection of the extract, using the BTEX volatiles-range column and a solvent delay so the DCM peak didn't blow up the MS. This worked well enough, though it was somewhat fiddly switching between PaT and direct injection, but we didn't have that high of a demand for samples. I rather wish we'd tried a hexane exchange on the extract and seen how that performed, but we never did.

If you need full list 8260 + 1,4-Dioxane in the same run that may be impossible to achieve with your specified RF with a traditional PaT. Dynamic headspace may have a shot but a CLP lab may not have that as an option.

[Ron]

There are EPA methods out there that expect the impossible, I don't know how they could ever have generated legitimate supporting data to put some things in methods. I have seen things where a basic knowledge of chemistry tells you the analysis will simply not meet the criteria. I think this is one of those examples.

What purge and trap system and trap are you using? That information may help but you may be fighting partition coefficients and purge efficiency.

My favorite sentence in an EPA method was in a method for monitoring aqueous effueunt from pharmaceutical manufacturing facilities. This isn't an exact quote, but it basically said to remove all the rocks, sticks, and small pebbles from the sample before proceeding with the analysis. The method is no longer useed because it simply didn't work. It involved purging polar compounds with non-polar internal standards. Sound familiar?

[LindseyPyron]

Based upon your email I assume you are running OI Concentrators with a #10 trap. This will cause serious moisture issues and peak resolution problems with the gasses.

[Ron]

That is true, if you run an OI with a dry purge and desorb preheat like a Tekmar uses the peak shape of the gases tends to be bad. If you run without the dry purge and desorb preheat, and with the trap starting temperature set low the gases should look fine.

[JI2002]

If you use 1,4-dioxane-D8 as the IS for 1,4-dioxane only, RRF should be around 1.

[msbonner]

Yes we are using a #10 trap. With a dry purge we can get a 0.01 RRf. but the gases do not work. Without the dry purge it is consistently below 0.006 RRf. Is there a better trap option for this application?

The method will not allow D8 dioxane for an IS it must be used for the Surrogate.

[Ron]

The dry purge does not remove much water and methanol from a number 10 trap, but it will affec the gases if the dry purge time is too long. A number 11 can be dry purged more efficiently.

[msbonner]

Thanks I will try the #11

[JI2002]

The method will not allow D8 dioxane for an IS it must be used for the Surrogate.

How about acetone-d6 as IS and 1,4-dioxane as SS?