Chromatography Forum

We get better results (for sensitivity, anyway) with rusty inlet frits (column inlet, that is) than with clean, white inlet frits. Same column, instrument, samples, eluents - just a different frit. Rusty frit = good; clean frit = bad. Like a light switch.

Anyone ever heard of such a thing?

I can't share much due to confidentiality, so I don't expect diagnostics. I just wonder if this'll ring a bell with someone.

I would say your rusty frit is starting a kind of ion exchange chromatography on stationary phase. That would mean your chromatography conditions (buffer, pH, solvent composition) are not at an optimum. You should get excellent performance also with a brand new column. Rusty frits are not good.

can you say what column you are using?
mobile phase?
method of run for the pump?

Hi
Rusty nut means one thing - your frit does not sit down in the saddle on the column. Most likely you tighten the nut with fanaticism and distorted saddle and carving on the column.
It is very likely that as long as you have a smooth nut - you have a mobile phase follows from the pipeline as the blood from the veins. A rust becomes clot ...

This is an ion exchange method with a quad-substituted alkyl amine on a latex-coated pellicular column. It's pretty clear that the "rust" is somehow improving column performance in terms of sensitivity. We're not seeing plate count affect either way (ie, at nominal analyte levels, there's no correlation in plate count - only at low levels do we see signal improvement). New columns appear to require a lot of "rust conditioning" before they'll work - simply putting a rusty frit on the front of a new column does nothing. But again, a clean frit on the front of a "conditioned" column eliminates the signal (ie, "is bad").

If no one has an "Aha - that must be an XYZ phenomenon...." answer, I'm just going to let this go. Management isn't interested in pursuing the issue and we'll probably find another method that works with less voodoo.

If the clean, new frits are white they are probably not stainless steel, and so would not rust in any case. I did have one case, working on some flavour compound whose name now eludes me but might have been n-methyl anthranilate or somesuch, when all of the analyte mysteriously failed to elute from SPE cartirdges. Fortunately the compound in question was fluorescent, and a couple of minutes under a UV light revealed it clinging tenaciously to the frit (probably polypropylene ?) at the top of the SPE column.

Peter