Chromatography Forum

Hello! I'm wondering if anyone has had experience with diethylene glycol dibenzoate contamination. I have a large peak from this compound that's causing problems with quantification of a co-eluting PAH peak in some dichloromethane particulate matter extracts.

As I originally thought that this peak was just from a garden-variety phthalate plasticizer, I've checked everything I can think of in the lab (pipet tips, syringe filters, gloves, Parafilm, my atmospheric sampling set-up, etc., etc.) but have found absolutely nothing.

Any ideas of other sources? There is also the possibility that this is actually coming from my samples themselves, but I haven't found any field measurements of this particular plasticizer, so it's hard to say.

Thanks very much,
Sarah

1. I don't know where this could be from.

2. Can you saponify to degrade the DEG dibenzoate and assay the PAH?

3. Since you appear to know that the interference is really DEG dibenzoate, I'm assuming that you are using GCMS. Is there an ion in the PAH that is not present in the DEG dibenzoate? If so, you could use extracted ion or SIM.

4. What about HPLC?

Hi! Thanks so much for the reply!

Unfortunately, LCMS isn't great for these samples, and even in SIM, the DEG dibenzoate peak is so huge by comparison (TIC is 6.5e7!) that the peak comes out a jagged mess.

However, I've managed to find the source of contamination: offgassing (I believe) from the lids of the amber bottles I was using for sample storage. The frustrating/weird thing about this is that the offgassing varies a lot between bottle lids AND that my blank samples, which were stored in identical bottles, didn't have the same contamination. I'm attributing this to the fact that the environmental samples had a film of particulate/organic matter into which the offgassed plasticizer could partition.

Anyway, here's the product information, in case anyone else finds this useful in future:

REDI-PAK WIDE-MOUTH BOTTLES
AMBER, 125ML
Z263133-1PAK

The offgassing appears to be coming from the actual lids, too, rather than the vinyl (in retrospect, a bad decision, although inconsequential, as it turns out) liners, so that's something to look out for, for sure.

Thanks again!
-Sarah