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analyte eluted earlier than solvent
Posted: Fri Aug 20, 2010 4:43 am
by Ramachandra
Hi all,
I am using HILIC column, my analyte peak was eluted earlier than solvent peak but the solvent peak was not interfere with analyte. It might be due to less polarity of analyte. Shall i use that method for my analysis.
Posted: Fri Aug 20, 2010 7:33 am
by Bintang
Most likely not.
Most likely you have either size exclusion or electrostatic expulsion from the pore volume of your column and if you have any other large or charged species in your sample you will have problems. It is always better to have retention of your sample.
Posted: Sat Aug 21, 2010 8:30 am
by Ramachandra
Thank you Bintang,
Actually, the analyte containing functional groups of -OH,-NH2,-RCONH-,-SO2- with molecular weight of 550, and its logp value 1.8. Even at 90:10(Acetonitrile:10mM NH40AC) mobile phase, the analyte (2.7 min) eluted within the solvent peak(2.9 min). What mobile phase composition will alter the analyte retention.
Posted: Sat Aug 21, 2010 4:59 pm
by Uwe Neue
If you are using a silica HILIC column, add some acetic acid to the ammonium acetate. This will make your analyte more polar.
Posted: Sun Aug 22, 2010 11:21 am
by unmgvar
did you try to run your samples in standard c-18 column?
what was the RT then? did the compound also go out before the solvent peak?
what is the K' value of the compound in C-18 separation?
Posted: Sun Aug 22, 2010 1:37 pm
by Ramachandra
Actually, my column is Zwitterionic-HILIC, I got analyte peak at 2.5min, solvent peak~3.5min and 10mM KNO3 at 5.1min (broad peak) with mobile phase composition of 90:10(Acetonitrile:NH40AC 20mM) at 0.5mL/min. i checked at pH:4.0 (NH40AC), eventhen no shift in retention time was observed. I think analyte is not retain at all, as said by unmgvar, C18 column may solve this problem. I have one more doubt, why solvent peak~3.5min and 10mM KNO3 at 5.1min (broad peak) eluted at different Rts? Whether the KNO3 is not a good volume marker for HILIC columns, like C18 columns?
Posted: Sun Aug 22, 2010 3:02 pm
by danko
You’re dealing with ionic interactions here!
Whether the KNO3 is not a good volume marker for HILIC columns, like C18 columns?
Of course not.
Best Regards
volume markers for HILIC columns
Posted: Mon Aug 23, 2010 4:04 am
by Ramachandra
Thank you danko,
what are the right volume markers for HILIC columns?
Posted: Mon Aug 23, 2010 6:44 am
by Bintang
We use toluene as void volume marker.
If you are using SeQuant ZIC-HILIC column you should contact our support at
support@mercksequant.com
Posted: Mon Aug 23, 2010 7:21 am
by danko
Hi Ramachandra,
Your analyte might be a good dead volume marker in this context
If you don’t see anything else that’s eluting prior to that - not even any disturbance caused by the injection, then it could be a good marker.
The final confirmation could be the calculated dead volume. If it’s nearly identical to the elution volume of your analyte then you’re safe.
Following that determination you’ll need to revise the method and make sure you achieve a reasonable retention of your analyte – for a start.
Another technique might be a sensible path to follow.
Best Regards