After several weeks of studying the effects of tetraethylammonium concentration on the elution of a strongly adhering sample, my retention times have suddenly increased dramatically. The only change during this time period was installing new column frits. Coincidentally (I think), the Rt's increased after the new firts were in and column pressure dropped from 200 bar down to 80 bar. Other info : Zorbax RxC8 column, 100% ACN, 40 deg C. Do quaternary amines such as TEAB "chew up" stationary phases? I've already run a "test mix", and those Rt's are shorter...perhaps indicating loss of C8. Any suggestions?

Since no one else has, I'll take a stab at this one. Disclaimer: I have no direct knowledge of the chemicals or column.

Most, if not all, of the column stability graphs I have seen published show steady degradation when the column is being damaged, as you suggest might be happening. If your RTs SUDDENLY changed after system maintenance, then something other than the column is perhaps at fault. Although you 'changed' the column, maybe the pumping system is acting up, causing these problems.

If your system pressure dropped at the same time the RTs stretched, I would suggest that is not a coincidence. You wouldn't be the first to have bizarre things happen to your system, as this forum has shown time and again. I personally chased drifting RTs for more than a week before finding a column compartment leak that nearly ruined my detector. It was a small leak--just enough to cause trouble, and it slowly kept getting bigger.

If you haven't already done so, go over every inch of your system.

You could see if you can duplicate a recent analysis to see if anything interesting happens. If you believe the column is the problem, then you have to prove that everything else in the system is ok, and that probably means doing a different (but hopefully similar) analysis.

Maybe the cost-effective way is to buy a new column. If ultimately the column is ok, you'll have a known good spare. If the column is bad, you'll need a new one anyway.