Matching frits with column inner diameter

[dkreller]

Hi,

I pack my own columns for column studies in the area of geochemistry. I have a selection of blank columns, all which are 1/4" OD (Restek), but that have 4.6, 3.2 and 2.1 mm ID's. Based on the reactivity of the packing material in the experiments I will use columns in a range of lengths and inner diameters. I am at the point of needing to replace some frits and when I look at the RESTEK catalogue I see that they sell frits based on different ID's.

I have to admit it is just dawning on me now that there are different frits for the different ID's. I have certainly gotten the frits all mixed up in time.

1. How serious of a mistake is it if I use a frit that is meant for a 4.6mm ID column on a 2.1mm ID column?

2. Similarly, how serious of a mistake is it if I get the frits mixed up and use a frit that is meant for a 2.1mm ID column on a 4.6mm ID column?

Thanks,

Dave

[tom jupille]

Code: Select all

1. How serious of a mistake is it if I use a frit that is meant for a 4.6mm ID column on a 2.1mm ID column?

Not very serious, but it depends a bit on the exact design of the frit and end fitting. Many columns use a 1/4" frit that extends all the way to to OD of the column. The part that overlaps the tube wall crushes down. If the design uses a central frit surrounded by plastic (which is what I'm guessing from the fact that you have different diameters available), then it *might* be a bit more problematic and add a miniscule amount of dead volume, but I doubt it would be large enough to measure.

Code: Select all

2. Similarly, how serious of a mistake is it if I get the frits mixed up and use a frit that is meant for a 2.1mm ID column on a 4.6mm ID column?

That might be more of a problem because it might change the flow dynamics at the column inlet. Ideally, the incoming mobile phase "oozes" through the frit so that the linear velocity is the same across the entire cross section of the column. A narrower frit would generate a "cone-shaped" flow profile and might result in loss of efficiency and/or peak shape problems. Unless your column is extremely efficient to begin with, however, I doubt that the change would be measurable.

Bottom line: probably not a problem, but you know where to look if it is!

[dkreller]

Thanks Tom,

BTW, I lived in Berkeley for a couple of years, and one of my best memories is a bike ride with a friend to the top of Mount Diablo!

That's near Walnut Creek, right?

Regards,

Dave

[tom jupille]

Yep. I actually have a great view of it from the outside door of the office.