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post-column obstruction

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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Dear all,
I am doing LC/MS analyses using capillary LC. I use 50 um ID Peeksil tubing. Most of the time this works fine. However, I sometimes get post-column obstructions. I find it difficult to find an explanation for these post-column obstructions. I can imagine getting pre-column obstruction, for instance due to sample impurities. Is there anyone that has an explanation for this phenomenon? My system setup is the following: Mobile phase A, 5 mM ammium acetate, mobile phase B, 97.5 % acetonitrile, 2.5 % water, 5 mM ammonium actetate. I run gradients from 10%B to 100% B. The flow rate is approximately 20 ul/min (I am using a flow splitter to get these low flow rates).

I hope someone has an explanation for this so I can change my setup and prevent these sometimes annoying obstructions.

Koen
Only speculation, but ammonium acetate is a pretty fair nutrient. Any chance you have some microbial contamination *inside* the column? I have no idea how you would confirm this, though. :(
-- Tom Jupille
LC Resources / Separation Science Associates
tjupille@lcresources.com
+ 1 (925) 297-5374
2 posts Page 1 of 1

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