Has anyone used monolithic column?
Did it significantly reduce your run time?
Did it improve column efficiency?
Any ideas?

Thanks

I've used the Performance RP-18e quite a bit. It is good for highly-retained compounds and for mixtures with large polarity differences between the components. The one drawback that I've seen is that many compounds show greater peak tailing with this column than they do with regular 5u C-18 particle columns.

When I proposed this topic earlier on, I thought the lack of response was due to deficiencies in the column technology. Well, people are finally looking into the chromolith column.

I recently did some work comparing a Comparator C18, 10cm, 4.6mm id., 3.5um particle vs Chromolith Performance C18, 10cm, 4.6mm id. Here are my observations:
1. Chromolith showed comparable related substance profile to the Comparator
2. Significant reduction in pressure (3X)
3. Significant reduction in run time (1/2) for late eluting compds
4. Can use gradient flow rather than gradient organic to elute late eluting compds even further without compromising resolution.

The chromolith column is excellent for fast method development. The related substance profiles were very reproducible. I plan to purchase some more and look at lot to lot reproducibility. I haven't seen significant peak tailing but I'll will keep it in mine.

How do you do the quantitation in gradient flow?

Very good question. We have done qualitative expt on gradient flow. Obviously, we need to somehow normalize the peak area to compensate for the gradient flow. I will have to get back to you on this one later.