Chromatography Forum

Hello,
I am using a poroshell c18 column (50 x 4.6 mm, 2.7 μm). The problem is that it gives very high pressure in short time. The first one that I used had been broken in about a month and the second just in 3 days. I am filtering the samples and my mobile phase is A) 2.4 g NaH2PO4 in 1 L H2O, pH 5 with NaOH 0.1 M B) MeOH and C) MeCN, Inj. volume: 7 μL. All are according to its manual so I can not understand if I am doing something wrong. Do you have any idea?

There is a diagnostic test you can run to establish whether a column problem is caused by the sample or the mobile phase. It's described on our web site: http://www.lcresources.com/resources/TSWiz/hs390.htm

if it's coming from the mobile phase, an in-line filter may help. If something in your samples is precipitating or sticking the the column, you may have to change the sample prep.

Thanks a lot!

I assume that this is the Agilent column? I got one for test, and it broke down very quickly (using friendly conditions). The system was blocked after the column, and it appeared as column material was leaking from the outlet of the column (a white slurry came from the outlet).

I got a replacement column, but I have not tested it yet. It could be a design flaw?

I really don't know, because after the second column I communicated with the supplier and they told me that they would replace it without giving me any explanation about the column behavior. Until now I haven't received the new one to known if there was a batch problem.

If it turns out to be a persistent problem for you, you can get the similar products from other manufacturers, such as HALO C18 (AMT), Kinetex C18 (Phenomenex), and Accucore C18 (Thermo).

What is the content of organic solvent in the final eluent?
Phosphate has very limmited solubility at high concentrations of organic solvent (the problem is accentuated if you mix the eluent on-line.)

It starts with 5% of methanol to 50% acetonitrile and drops again to 5 % of methanol for equilibration.