coelution
Posted: Mon Mar 07, 2005 2:10 pm
in column H+ with water acidified mobil phase (H2SO4),flow of 0.6 ml/min and 55°C, i cannot separate lactose and ammonium citrate. can you help me. Thank you[/i][/b]
From your conditions, I assume you're talking about a cation exchange column in the H+ form. Those columns are designed and sold for fairly specific applications. The first thing I would do is to check with the manufacturer to find out if that column is supposed to separate lactose and citrate.
Things you can do to try changing the selectivity:
- change the temperature. The high-temperature is required for glucose (and glucose oligomers) on Ca++ form resins (otherwise you get partial separation of alpha and beta glucose), but as far as I know, not required on the H+ column.
- change the pH. The degree of ionization of citrate will affect its retention, lactose is neutral.
- try adding organic modifier (ACN). That will tend to make everything elute faster, but it can also change selectivity.
Good luck, and let us know how it works out.