Chromatography Forum

issue : Retention time shifting

in ion chromatography

instrument: metrohm

column : metrosep A supp1 250

mobile phase : 0.318 gm in 1000mL water

detecion: sulfate

initial Rt :24(very 1st injection) and after 100 injections its 21

can any one suggest any solution for it

thanks in advance

is the RT 24 throughout the first 100 injections and then suddenly 21 min at 100? Or is it a gradual change from 24 min to 21 throughout 100 samples? Does it go back to 24 on its own or do you have to do any maintenance (e.g. backflush column etc.).

is the RT 24 throughout the first 100 injections and then suddenly 21 min at 100? Or is it a gradual change from 24 min to 21 throughout 100 samples? Does it go back to 24 on its own or do you have to do any maintenance (e.g. backflush column etc.).

Through out the analysis/or till the 100 inj(its not the exact figure) runtime was 24 and for the next time when i performed the analysis its 21 I tried with diff systems, diff M.phase, at-last when i tried with new column it was again 24
and one more thing is that the old column which i was getting 21 reduced its Rt.

How long did the column sit between those sets of runs? what was the storage buffer (and what did the manufacturer recommend). It looks like your column is dying during storage.

How long did the column sit between those sets of runs? what was the storage buffer (and what did the manufacturer recommend). It looks like your column is dying during storage.

the mobile phase which i run is sodium carbonate anhydrous(0.3 gms in 1000mL water) buffer, and its the storage solution recommended by the column vendor

All the symptoms point to the column deteriorating, so the next step would be to contact the vendor.

what is the sample matrix?
back pressure on the column (initially and with reduced RT?

what is the sample matrix?
back pressure on the column (initially and with reduced RT?

yes the pressure is gradually increasing
initial - 7.8
present - 9.4

what is the sample matrix?
back pressure on the column (initially and with reduced RT?

the sample matrix is enoxaparin injection

Are you using a Guard column?

If yes, how is the back pressure without Guard?
Did you replace the guard column?

If no, check with Metrohm India about column regeneration on this application.