By johnboy on Thursday, October 31, 2002 - 09:10 am:
an analysis a colleague of mine is using is going through a number of cyano columns. brand new columns are apparently showing a strong degree of tailing when chromatographing a compound containing thiazole, pyrimidine and N,N-dialkyl amine groups.
the mobile phase is 50 mM sodium acetate (pH 5.1 with acetic acid) with an acetonitrile gradient formed by on-line mixing in a 2695 Alliance.
it's a bit concerning reading the column log which shows a handful of entries followed by "returned to manufacturer".
everyone else have such bad luck with this phase?
By johnboy on Thursday, October 31, 2002 - 09:32 am:
sorry it should read something like "brand new columns soon start to show a strong degree of tailing..." that is, brand new columns do not tail on the first analysis.
By dm on Friday, November 1, 2002 - 04:09 am:
CN phases simply are not stable. The only one tat is close is the Zorbax StableBond. With all others you are unfortunately wasting your time if long-term stability is a criteria. Another much easier option is to try another ligand.
The shorter the ligand, the less stable the stationary phase.
By Gerhard Kratz on Saturday, November 2, 2002 - 01:31 am:
Johnboy, as dm already mentioned, CN phases are not very stable, no matter who is manufacturing them. You have 3 possibilities: go for the cheapest CN column on the market, and life with returning most of them, but you will waste time. Or you can try other stationary phases, like RP with embedded polar groups, or better HILIC columns. Also CN is a kind of HILIC phase, but not stable. Other modifications are more stable. For your compounds I would recommend a stationary phase modified with an Amide structure, like Carbamoyl. Please feel free to check out our webside www.tosohbiosep.de and have a look on Amide-80 column. Very useful information on such phases you can get also from Uwe Neue's book. Good luck.
By Anonymous on Wednesday, November 6, 2002 - 11:14 pm:
WHAT THE HELL IS GOING ON HERE???
Please Mr. Moderator, can you block this "genius" Baldasso???
Mr. Baldasso, I must admit...a very nice work of diligence, but unfortunately no work of intelligence...
By Moderator on Thursday, November 7, 2002 - 10:18 am:
Regarding the previous comment by Anonymous: We removed Mr. Baldasso's entry. Our users have been extremely helpful in keeping the Chromatography Forum discussion group professional and respectful.
Moderator
By Einar Pontén - SeQuant AB on Tuesday, November 12, 2002 - 02:42 pm:
Dear Johnboy, I agree with Mr Kratz that HILIC could be an alternative. Although, you use a quite mild mobile phase, still the CN phases are not stable in your application. We are currently testing the ZIC™-HILIC column, having a covalently bound zwitterionic functional group on silica, for the separation of some N-alkyl pyridines. We use mobile phases similar to the one you mention and would be pleased to send you application data later on (send us an e-mail). Einar Pontén, http://www.sequant.com
By Anonymous on Tuesday, November 12, 2002 - 04:37 pm:
Mr Sequant: do you have any data comparing the stability of your packing to the stability of a CN, or any reason why your column should be better than a CN?
By Einar Pontén - SeQuant AB on Wednesday, November 13, 2002 - 01:12 pm:
Stability ZIC-phase
As indicated the method development for the separation of N-alkyl pyridines by ZIC-HILIC is in preparation. We have not made a comparision with CN-phases, so I have no comment on their stability.
According to our data on the ZIC phase (presented at PrepTech 2002) it was not significantly affected after one month when kept in a buffer solution between pH 2 to 8 at 50 °C.
One could suspect that a highly hydrophilic support like this would degrade due to access by nucleophiles. This is not the case. The "50 mM sodium acetate (pH 5.1 with acetic acid)" should not cause any problem.