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Short column lifetime due to sulfuric acid in samples?

Posted: Thu Jan 10, 2019 5:41 pm
by mwijland
Hi all,

at this moment we analyze phenolsulfonic acid (para and ortho) using hplc and a Waters xbridge phenyl column (in a 10 mM ammoniumcarbonate buffered system). At this moment the samples are simply prepared dissolving the samples and neutralizing the remaining sulfuric acid in the samples using sodium hydroxide and filtration of the samples. The column lifetime is very short and I wonder if this could be caused bad sample preparations. Any ideas about this or suggestions?

Regards, Mark

Re: Short column lifetime due to sulfuric acid in samples?

Posted: Thu Jan 10, 2019 9:00 pm
by Rndirk
What kind of samples are you analyzing? How many injections does a column last and what is the symptom of the loss of performance.

Any more details about both the sample preparation and the LC method (injection volume, temperature,..) would be helpful.

Re: Short column lifetime due to sulfuric acid in samples?

Posted: Thu Jan 10, 2019 10:07 pm
by mwijland
Loss of performance is shown by extreme peak tailing. The injection volume is 10ul @ 1ml/min and column temp is 30C. Elution program is 100% buffer for 5 minutes and from 5.01-12 minutes 90-10 acn-buffer. Column lasts only about a hundred sample injections (or in that order of magnitude).

Re: Short column lifetime due to sulfuric acid in samples?

Posted: Thu Jan 10, 2019 11:13 pm
by Consumer Products Guy
I thought you said you neutralized the sulfuric acid in your samples?

Anyway, why not inject like 3µl or 5µl instead if you think your samples are the cause of the short lifetimes; with your stated analytes you should have plenty of sensitivity.

Re: Short column lifetime due to sulfuric acid in samples?

Posted: Fri Jan 11, 2019 11:23 am
by HPLC chemist
Sounds like your column is being 'fouled' by excipients in the sample. What else are you injecting?

Re: Short column lifetime due to sulfuric acid in samples?

Posted: Fri Jan 11, 2019 12:25 pm
by Rndirk
How do you prepare the buffer and what is the final pH ?

Are you sure this buffer is compatible with acetonitrile: could there be precipitation if you mix ~10mL buffer with ~90mL acetonitrile?

Re: Short column lifetime due to sulfuric acid in samples?

Posted: Mon Jan 14, 2019 10:27 pm
by Vlad Orlovsky
I don't think that your problem is related to having sulfuric acid in your sample. Even if you don't neutralize it before injection you are injecting only 10 uL with 1 ml/min buffered mobile phase. May be your pH is too high. There is no reason to run your compound at high pH. You can use pH 2-5 and most likely not lose any retention (you might gain it at lower pH)