Chromatography Forum

hi

I would like to know about the methods or strategy for “On-Line Preconcentration of Sample in liquid Chromatographyâ€

Simple: if your diluent (what the sample is dissolved in) is much weaker than your mobile phase, you can inject a very large volume and the analyte molecules will "stack up" on the head of the column or guard cartridge.

thanks tom

we have been doing the same for some of our samples, so in some samples we end up making large multiple injection ( the only problem i see in this is that there is always a question on sample diffusion in sample loop etc...) i reason for my post was i have seen some articles regarding On-Line Preconcentration of Sample in capillary electrophoresis and in some ion exchnage i was wondering if there exist any method or strategy for protein samples for liquid chromatography (mainly for IEC and RP )???

Here are links to 3 application notes that cover this subject. These notes provide a great review of both online preconcentration and the complementary technique for online sample-cleanup.

The plumbing diagrams for 6port and 10port injection valves are also included for both techniques.

http://www.optimizetech.com/opti-shop/lit/an101.pdf

http://www.optimizetech.com/opti-shop/lit/an102.pdf

http://www.optimizetech.com/opti-shop/lit/an103.pdf

On-Line Preconcentration of Sample in capillary electrophoresis and in some ion exchnage i was wondering if there exist any method or strategy for protein samples for liquid chromatography (mainly for IEC and RP )???

It's the same principle in all of those cases. If your protein is dissolved in a weak solvent (aqueous buffer for RP; low ionic strength or a pH on the "wrong" side of the pI for IEX) *and* if the injection volume is large enough that relatively little mixing with the mobile phase occurs, then the protein will accumulate on the head of the column and you will get a reconcentration.

How large a volume is usable (or required) depends on the difference in eluant strength between the diluant and the mobile phase and on the mixing characteristics of your system, so it's difficult/impossible to generalize; you have to experiment and see what happens.