Chromatography Forum

Hi,

I have a C18 column, and i use a buffer (phosphate) pH 7, methanol (99-1%)(v/v) as a mobile phase.

What is the best way to flush this column, and remove buffer, because i am afraid that i can not use ( water-methnol) (99,1%)(v/v).

Thank you.

First (question): if you can use 99% buffer in the column, why can you not use 99% water?

Second (comment): phosphate buffers are reasonably soluble in methanol/water, so unless it is *very* concentrated (I'm talking above 100 mM), I would be surprised to find any precipitation issues with higher Methanol percentages. Just to be safe, try mixing different ratios of your buffer and methanol in a test tube and hold it up to the light to look for "sparklies".

I agree with Tom.
You can flush your column even with 100% water to wash out your Phosphate buffer. Did you had a look on volatile buffers?
Good luck

Thank you ;

Now i am using ACN/H2O ( 70/30 %)(v/v) to flush my column.
I will try to flush the column with 100% water.
And about the volatile buffers , can you give me some examples of volatile buffers used in HPLC.

I'm a big fan of ammonium acetate. It can be used to buffer at pH 3.8-5.8 and 8.2-10.2. My source is "LC/MS: Apractical User's Guide" by Marvin C. McMaster.