EPA 515.3 Base Promoted Esterification

[musicdds]

With the shortage of Diazold I am trying to perform EPA 515.3 using tetrabutylammonium hydroxide and methyl idodide. First try was a complete flop. I literally have no peaks except for a small blip for my internal standard. Has anyone had any luck with this procedure? I did not do the florisil clean up step but doubt this would be the problem. Any advise would be greatly appreciated.

Thanks,

Denise

[James_Ball]

I haven't tried this for the 515 method but I did use that procedure a lot back in college doing research on coal and it would methylate almost all of the -OH groups present as that band in the IR spectra would disappear. After 30 years though I can't remember if moisture in a sample would cause it to fail, if it does then you may need to try the solvent before proceeding.

[twranger]

We are looking into this as well, I tried a few LCSs spiked directly into solvent, had excellent recovery except for dinoseb, which is zero. Method says they got 40% recovery, so I will try again.

Has anyone heard a reason from Aldrich for the shortage? All the EPA methods call for its use.

[Jake]

Just throwing things out there: Would it be possible to substitute trimethylsilyl diazomethane for Diazald/diazomethane? Works well as a stable substitute for diazomethane.

(note: read precautions on its use; there have been deaths associated with its use, but my understanding is those were associated with very large scale use or manufacturing)

[Bigbear]

In the past we used diazomethane for months. It is effective when stored at -80C.
We got dinged during an audit as the reference method states 72 hours when stored at 0-5C.
Has anyone asked that they be allowed to use diazomethane for longer than 72 hours?

[Bigbear]

Update.
We asked our auditor if we could use diazomethane beyond the 72 hrs when stored at 180C. The auditor bounced it to Cincinnati and this is what we got.
I spoke with EPA in Cincinnati about your question whether or not the diazomethane solution in EPA 515.4 can be used beyond 72 hours for the esterification of samples. Steve Wendelken, one of the authors of the reference method, explained that the 72 hour period quoted in the method is not a firm expiration and continued to suggest your laboratory document the performance between the diazomethane solution freshly made (<72 hours) and the diazomethane solution held beyond the 72 hours to establish defensible data to back up an extended expiration time. You should review his explanation on how to document such a study and verify whether or not the studies your laboratory performed are sufficient, such as running high standard duplicates. This is what he said:

“The 72 hour period was the rule of thumb used in the lab when the method was developed. We never conducted any storage stability studies beyond 72 hours since it was an unlimited resource then. Since this time does not reflect a point where we know it “goes bad”, I don’t think it would be unreasonable to look at extending the holding time. I would back this up by collecting stability data running duplicates of a high standard (the highest derivitization demand) using the “old stored” vs fresh as they run batches to establish how long it is stable. This would allow them to defensibly extend the hold time and conserve reagent until supplies are restored.”

I have done studies using diazomethane prepared on 10/25/16 compared to "fresh" over 7 months. I extracted 2 extra CCS's with every batch and esterified them with the "old" diazomethane. I'm now "prettying " up my data.
I'll keep you posted as to how Cincinatti likes it.

[palawast]

Fillgoods

[James_Ball]

We are looking into this as well, I tried a few LCSs spiked directly into solvent, had excellent recovery except for dinoseb, which is zero. Method says they got 40% recovery, so I will try again.

Has anyone heard a reason from Aldrich for the shortage? All the EPA methods call for its use.

When contacting Aldrich recently they have discontinued selling Diazald. Apparently there is only one plant in the world that produces it and they have had trouble getting a reliable supply. Diazald is their rebranded name for the actual chemical, but you can purchase it from other vendors under the exact name(which I don't remember off hand, our extraction manager has been ordering it though). Even then we have been waiting sometimes months for delivery, so EPA definitely needs to look into updating a method to work around this problem.

The most simple method would be to use LCMSMS and not need derivitization. Those analytes respond well using MRM. HPLC-UV can also work but not quite as sensitive.