150 mM sodium phosphate

In the SDS for the column Agilent Bio SEC-3 column you have stated to clean the column 150 mM of sodium phosphate at pH 7 is used. I was wondering how you made that 150 mM of sodium phosphate

  • Hello,


    To clarify, we don't recommend cleaning the column with 150 mM phosphate buffer.  150 mM phosphate buffer at pH 7 is a common mobile phase for analyzing samples, but not for cleaning.  Suggested cleaning solutions can be found on page 2 of the user guide.


    The phosphate buffer used for sample analysis is made from a mixture of monobasic and dibasic sodium phosphate (NaH2PO4 and Na2HPO4) so that the total phosphate concentration 150 mM and the pH is 7.  Exactly how much to weigh out depends on whether you have anhydrous or hydrated sodium phosphate salts. 


    I typically use our Buffer Advisor software to calculate exactly how much salt to weigh out.  For example to make 1 L of 150 mM phosphate buffer at pH 7 would be:

    16.559 g sodium phosphate monobasic monohydrate (NaH2PO4 * H2O)

    31.231 g sodium phosphate dibasic, anhydrous (Na2HPO4)

    in 1 L of water


    Again, those weights will be different with different hydrated forms of sodium phosphate.


    I'd recommend stopping a few mL short of 1 L, measuring the pH to double check it, adjusting it if needed, and then once the pH is at 7, filling up to exactly 1 L.



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