Chromatography Forum

Hi all,

I'm developing a HPLC-MS assay for a couple of quaternary ammonium herbicides and am trying to steer clear of ion-pairing agents (TFA,HFBA) by using a HILIC column to separate them.

I've got a bare silica HILIC column and am able to separate both of my compounds but need to use a fairly high concentration of ammonium formate buffer (100mM) to get a decent peak shape and even then there is still pretty bad tailing (posible due to ion-exchange intereactions with silanols??).

I noticed that the ZIC-HILIC column has a different stationary phase with an attached zwitterion and was wondering if anyone had experience separating quats on this type of column.

Thanks

Stephen

An alternative to "HILIC" mode is RP + IEX. Below is an application for organophosphorous pesticides
and quaternary ammonium herbicides on Scherzo SM-C18 (C18 + anion + cation ligands):

http://www.imtaktusa.com/site_media/fil ... TI555E.pdf

Here a dual gradient was used - increase in organic and salt with time.

Here is an ISOCRATIC method for paraquat and diquat which was validated in two agricultural companies in US and Europe:
http://www.sielc.com/application_180.html
You can use 50-100 mm column and analyze these quats in 5-6 minutes

Also this approach is used in Australian company (can provide you a name in a private message)