Sample preparation and Column cleaning

[Dedi]

Dear All members,

This is my first post to this forum, thx to mr syx for introducing me this forum, do you still remember me? I guess you are Mr. Siswanto from Interbat?

We're developing a method of analysis by HPLC from OBH syrup formulation. We didn't do clean up sample preparation, we just dilute the sample by mobile phase, filter by miliphore 0.45 micron, then inject to the system. The method is satisfy for certain time of analysis by new column package, but the column is quicker blocked and become high back pressure than others method. we use Lichrospher 100 RP-8, 5 micron.
is it OK for the sample preparation, due to the sample matrix is viscous?
why the column is quicker blocked than others method with the same mobile phase and column cleaning procedure?

Any suggestion for effective column cleaning program?

Thank you

[sassman]

Was the other method that did not cause a problem with the column using better sample prep? It would be best to dilute your sample in methanol or acetonitrile and pass it through a solid phase extraction cartridge before running on HPLC (perhaps instead of filtering). This way you can be sure that you will not cause a serious problem with the column. I suspect that you have some strongly sorbing components in the sample (PEG maybe?).

If you don't want to do SPE prior to running the sample, you are going have column problems I am afraid. You can try washing it with acetonitrile or methanol, and if that doesn't work something stronger like isopropanol at a low flow rate. If that doesn't work, ethyl acetate or dichloromethane as a last resort. Never switch from one solvent to another that is not miscible with the first. You can try to backflush the column also, but ask the column manufacturer if it is OK first. Some columns do not like to have the flow reversed.

[Dedi]

The other methods is the same mobile phase but different sample matrix.

Yes, I think so. The sample matrix contained PEG and Succus liquiritae.

How about using Monolithic column? can it help?

[Mark Tracy]

PEG does not irreversibly bind to RP columns; in fact it will elute near void. There are plenty of colloidal materials that will pass a 0.45µ filter, but get caught in an HPLC column. I recommend using a guard cartridge and changing it at the earliest sign of high pressure.

Also, if the sample is highly viscous even after dilution, it can damage some columns. Use as much dilution as your requirements for LOQ will permit.