MEmory effect?

[Aurelien]

Hey guys,

I was wondering if someone could tell me about memory effect, or send me link that explains what it is.

Thank you very much

Aurelien

[mohan_2008]

Memory effect is a term used to express "Carry-over".

This can be a analyte carry-over as in HPLC.

For eg: Using a weaker mobile phase may not completely elute the required analyte. Subsequently, the analyte will build up on the column head, and gets washed off/eluted at a later time. A blank is injected after each sample injection to evaluate this "Carry-over" of the analyte or any late eluters.

This carry-over poses great problems specifically in gradient elution, hence only HPLC-grade solvents are used.

[Noser222]

I've also seen sufficiently hydrophobic molecules sticking to the injector seals and causing carryover.

[Bruce Hamilton]

My understanding of memory effect, as it applies to HPLC columns, is somewhat different. However, there are several posters here who know such things and will clarify, and will inform us that I'm wrong ( as usual ).

My understanding is that some column types were known for "memory effects", perhaps after exposure to mobile phases with modifiers, such as amines, ion-pairing agents etc.

They retain modified separation ability long after the modifier has been removed from the mobile phase. Modern columns tend to have much less "memory effects" than earlier columns. IIRC, triethylamine was one of the culprits.

In MS, "memory effect" may be defined differently, perhaps waiting until the baseline settles after an injection, but MS is not my game...

"Carryover" results from material, usually present in sample/standard, appearing in subsequent injections, and is often a function of instrument design or the sample.

Please keep having fun,

Bruce Hamilton

[mohan_2008]

I agree with Bruce completely.

It is true that after running an ion-pair method/ or using a basic modifier such as TEA - will alter the reversed-phase properties of a column.

As it is difficult to rinse-off the TEA or ion-pair completely from the column, the column now will exhibit modified reversed-phase characteristics as compared to a new/fresh RP column.

This can be constituted as a true Memory effect.

I translated this definition of a carry-over toward Memory effect, from the ICP analytical perspective. In an ICP, some of the analytes hang-in the nebulizer and never get completely transfered to the plasma torch.

These analytes keep getting carried over, per every nebulized sample and give erroneous reading. This is pretty similar to the "Carry-over" description that I mentioned earlier.

[HW Mueller]

We discussed this many times, if part of the analyte sticks to the column you get immense tailing. A carriover peak can only result if the system is jolted somehow, via solvent bolus, etc.