Chromatography Forum

Currently I am using a YMC Pack Pro C18 column which is stated to be stable within the pH range of 2.0-8.0 and compatible with 100% aqueous phase. And the method I am using involves high percentage (98-100%) of acidic aqueous phase (0.1%-0.5% formic acid) pH about 2.45-2.8.
I remember in some posts, tom jupille mentioned that endcapping comes off very quickly at low pH but C18 is so hydrophobic that under highly aqueous condition, it is likely to stay in position long enough for the bond to reform, which means the loss of bonded phase occurs relatively slowly as long as % phase B is kept low.
In my case, I have to use the column quite often, maybe every other day so I wonder if I can leave the column at such high percentage of acidic phase A without flushing the column with high percentage of B at the end of the day after finishing using it. Does it damage the column or reduce the lifetime of it?
As I am gonna use this column pretty much for all analysis for my graduate research project, would you please give me some advice as to how to maintain the stability and avoid the collapse of the column under such a running conditions?
Thank you!

I would check with YMC for their recommendations on that specific column. In general, you will get the longest column lifetime storing in either 100% organic or 50/50 organic water (opinions vary on that one!). There are two catches to that:
1. It's always dangerous to reason from the general to the specific!
2. You can spend a lot of otherwise useful time flushing the column out and then re-equilibrating the next morning.

In the absence of more specific advice from YMC, I'd go with 100% ACN.

Hi Tom,

Thanks for the response. Actually my normal routine after using every column at the end of the day is to flush it with 70% organic phase. But for this particular column, I have some concern as I run it at highly aqueous acidic phase. Because you mentioned that under that condition the bonded phase C18 comes off very quickly, I am afraid if I flush the column with such a high percent B at the end of the day everyday, those C18 will be washed off, which may soon degrade the column.
So if I have to use it everyday, isn't it better to leave it that way so that I the C18 bonded phase coming off still hangs in there and have more chance for the bond to reform and I don't have to spend too much time equilibrating the column the next morning?

I see what you mean, but actually, the story on hydrophobicity stabilizing C18 at low pH is that it holds the C18 group in place long enough for the broken silyl ether linkage to reform. By that argument, subsequent exposure to 100% organic won't do anything bad.