Chiralpak AD column kaput?

[thiazole]

Curious if anyone has any experience with a Chiralpak AD column when it is "spent". I've got one that used to work great, but it seems the last few compounds I've analyzed have taken far less IPA than the literature uses (ie, it isn't retaining as well) and the separation doesn't seem as good as the literature. The thing is, I never seem to analyze the same compound twice, so I can't know for sure unless I dig up an old sample, but curious if this is how they go. Any other signs?

[thiazole]

Turns out the column was bad. A new column was a world of difference. It both retained better and separated the enantiomers better.