Chromatography Forum

Respected Forum,

I am a newcomer to chromatography, i just would like to know how to avoid tailing using column prtreatment? Is this technique better than using organic modifiers? for routine purposes which of the above technique would be suitable??

Aniket
Nicholas Piramal Research Center,
Mumbai, India

Dear Aniket,

What kind of technique du you have in mind – Reversed Phase, Ion Exchange, Size Exclusion?
Do you experience tailing, or is it just a theoretical question?
If you do have a problem with tailing, please describe your method of analysis and ideally send a chromatogram.
Generally speaking, column pretreatment is seldom viable and should not be considered as a standard procedure.

Best Regards

I strongly recommend to stay away from column pretreatments. Most, if not all, manufacturers go through sufficient pain to produce a reproducible packing. The idea is that you can purchase the same column wiht the same characteristic again. If you do some magical pretreatment of the column yourself, you will have lost any guarantee that you will see a column with the same properties again.

The packings of major manufacturers with a lot of experience are very reproducible. For some packings, the reproducibility that has been achieved is better than the mesuring ability of the average chromatographer. If you do your own pretreatment, you loose all this immediately.

Column Pretreatment is a euphamistic way of saying:
"I developed a method on a column that had its selectivity altered by some ion pairing agent and it's easier to make method users alter their columns than it is for me to redevelop the method."

Dear Forum,

Thank you all for sharing your wisdom. This was just a theoritical question from my side, i dont have any representive chromatogram to show.

I am frequently using Trietyl amine in my mobile phase, i heard that it binds irrevrsibly to the free sillinols. Does that account to alteration of the column from the original properties? How do i remove TEA in my column?

One more question are they any new kind of stationary phases where i do not need to use organic modifiers such as Triethylamine??

Sorry if i am annoying you with some basic questions.

Thanking You,
Aniket

A big Helow to all from India!!

Does that account to alteration of the column from the original properties?

almost certainly, Yes

How do i remove TEA in my column?

you can't, in a reasonable amount of time - consider the column to be "unique"

any new kind of stationary phases where i do not need to use organic modifiers such as Triethylamine??

Look to columns that demonstrate good peak symmetry with basic narcotics or amitriptyline for starters. If you still see too much tailing, there are ionpairing agents other than TEA that may prove helpful without altering your column's selectivity nearly as much. There are others who frequent this board who will almost certainly offer some more specific suggestions.

Following up on DR's lead:
Without question, more modern columns will improve peak shape to the level that you do not need TEA. I have spend the last dozen years or so involved in developing columns that do not need TEA. Starting with Symmetry, and ending up with XBridge. You will be an immediate convert to the idea that modern columns are better, if you use a column with an embedded polar group: SymmetryShield RP18 or XBridge Shield RP18.

Thank you all Respected Chroamtographers for answeing my queries,

So what i follow from your replies is that It is wise to use best column, rather than trying to better a good column.

Currentlly i am using Hypersil BDS c18, Xterra C18 columns, so i just wanted to ask about the difference in say Xterra c18 and Xbridge c18, can you please elaborate on these issues?

Should i switch to these modern columns, or the old colimns which are working ok with TEA?

Please advice me on this
Aniket

XBridge gives sharper peaks than XTerra. In addition, I would recommend the XBridge Shield RP18 as the best overall option (practically no tailing for basic compounds).