Some papers have suggested to use ortho-phophoric acid, aceonitrile, etc? How do you adjust the mobile phase's pH concentration? Can I adjust it using 1.0 M of H2SO4 or NaOH, respectively? Or must I use the buffer to adjust the pH level? Kindly drop your opinions and comments here. Thank you.
I never analyzed lactic acid, but in general a C18 column should be appropriate for detecting acids.
In general, a buffer 2 pH units above or below the pKa of your analyte should be chosen for a good peak geometry (think of the Henderson-Hasselback equation).
And please adjust your pH with phosphoric acid to avoid having foreign ions in your buffer.
Good luck.
never use H2SO4 or NaOH or any other strong acid or base to adjust pH. it will damage the column and whole system because of their corrosive nature.
use orthophosphoric acid, glacial acetic acid or formic acid to make acidic and triethylamine to make it basic.
pH could be adjusted between 3-6.5 for c18 column otherwise column will get damaged.
Thanks for willing to share the experience.
I am doubt about the methods (journal & column technical guide) to prepare the mobile phase.
In journal paper, just written the use of 0.2 M phosphoric acid as mobile phase to detect lactic acid. flow-rate is 0.5ml/min. UV 210 nm.
However, by using the supplier's column (Thermo brand, Aquasil C-18 column), the column technical guide would suggest to use 1% Acn / 99% 0.05M KH2PO4 (pH 2.8) as mobile phase. Flow is 1.25 ml/min. UV 210 nm.
Could anyone comment on this? And which protocol should I follow in order to lactic acid?
Thank you.
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