Chromatography Forum

our API is free acid. We are using Ascentis RP-amide column at pH9. I notice this column is good 2-7.5. Are there any other RP-amide columns that are suitable at pH9?

what is an amide column good for?

Can I just use normal C18?

Thanks a lot

I recommande to use a column which is very stable at low pH for your application. I recommande SiliaChrom SB C18 wich is very stable at low pH as 1.0 without any bleeding and degradation. More powerful for your application
Charles

A column with stability from pH 2 to pH 12 is the XBridge Shield RP18, with an embedded carbamate group.

"what is an amide column good for?"
just a type of column with stronger retention of polar analytes than C18

if it says up to 7.5 why do you use it at 9.0?
there are columns stable at higher pH similar to one you use, XBrige which was mentioned is an example of such

don't ask if you can use it - just do it - try and learn
i would suggest using acidic mobile phase - so your acid is neutral and not deprotonated which is the case when running under high pH
when it is neutral it's retention will probably increase and you will get it away from the dead time which is desirable I think, unless of course you already have sufficient retention

but this is only suggestion, i don't know your case, you must decide for your own

I am so annoyed with the name of this column. I love the Tosoh amide column for HILIC of sugars etc. The new Waters amide column is also excellent. I bought the Ascentis amide column thinking that it would be fantastic only to learn it is a reversed phase column with embedded amide groups.

Consequently I can say with authority that the Supeclo Ascentis amide column is ABSOLUTELY the worst HILIC column you could ever hope to waste money on.

Consequently I can say with authority that the Supeclo Ascentis amide column is ABSOLUTELY the worst HILIC column you could ever hope to waste money on.

I would disagree. A C18 column would probably be worse for HILIC.

First, "amide" columns are just that: a reversed phase column with an amide functionality in the hydrocarbon chain. It is not a HILIC column and I do not believe that it is marketed that way.

Amide columns are particularly retentive of acids, relative to a standard reversed phase column. However, to take advantage of this effect, you must have your acid in the neutral form. As suggested, make your mobile phase acidic. I have used this column successfully with several different mobile phases, including 0.1% phosphoric acid and 0.1% sulfuric acid.

I ran more than 500 injections at very high acidic condition more than 1.5% of TFA and phosphoric acid. No modification for my mixture after many days (15 days). My column is SiliaChrom SB C18. Does anybody have better column for that kind of mobile phase. It is so great to analyse acid compound (non-ionized analyte)