Chromatography Forum

Hi,

I am facing a major issue with the storage of stock solutions of Haloacetic Acids in MTBE, despite we have tried everything available in literature in terms of temperatures, storage vials etc, still we have the standards degrade within 2-3 days and QC failing.

Do you have any recommendation how to handle and store the stock solutions after opening the ampule to avoid this degradation.

The costs are out of the roof, as we have ended up buying and using new standards for every run, in order to be able to catch the QC requirements of the method. (EPA 552.3

Thanks,

We run 1.01995.2500 from millipore and a custom concentration stock from Agilent. If you're going high I'd check the seals on your vials. Low or inconsistent across batches would point me to prep error. PDS works fine.

Thanks for your kind reply,

We are confindent we dont make any mistakes during the prep, as the first time we open the ampule and use the standard, we face no issue at all with the QC.

After 3 days , or even 2, we get inconsistent results without any reasoning (not consistently low or constistently high), while the duplicates match.

After opening first time the stock ampule (I assume then you partition it in other bottles, correct?) how long do you expect it to last?

Six months, it still passes but method says re-prep at that point.

What are you comparing? With 552 you should only have two standards, a first and a second source. All QC and calibration go though the entire extraction process.

Are you getting variability within batches or between batches? 552 methylation is very sensitive to any changes, we extracted a new calibration with every batch.

Hi all,

Thanks to those who’ve shared diagnostic steps and practical fixes!

For anyone else encountering issues with MTBE stock solutions, I wanted to share an article that covers common causes, troubleshooting strategies, and a few workarounds:

Stock Solution Stability in MTBE Solvent: How to Prevent Degradation and Preserve Sample Integrity

Hope it’s helpful for anyone looking to dig a bit deeper.

Best,

Shiama