Particle size? Pore size?

[firework1]

The label on an HPLC column always tells something like: 4.6*150mm, 5um, 100A......

I assume 5um is the particle size and 100A is the pore size. Is this right? Someone corrects me?

Is there any correlation between particle size and pore size? Is it like the smaller the particle size, the smaller the pore size? Or are they totally independent?

I understand that there is an optimal pore size for each analyte if you care to look into the molecular size.... How about the particle size? Since smaller particle size yields greater column efficiency, is it always better to use smaller particle as long as pressure doesn't built up too high?

[tom jupille]

5um is the particle size and 100A is the pore size. Is this right? Someone corrects me?

That's correct.

Is there any correlation between particle size and pore size? Is it like the smaller the particle size, the smaller the pore size? Or are they totally independent?

Totally independent unless you get to very small particles and very large pores. 100 Ã… = 10 nm = 0.01μm. If you have a 1.7 μm particle (small by today's standards), the particle diameter is 170 times the pore diameter. If you had a 1000 Ã… pore size (huge by today's standards), your particle would still be 17 times the pore size. That's about the same relative dimensions as the finger holes in a bowling ball.

Since smaller particle size yields greater column efficiency, is it always better to use smaller particle as long as pressure doesn't built up too high?

That is a "can of worms"! Do a search on "particle size" and you'll find some very spirited discussions of particle size effects. If you are pressure-limited, very small particles may force you to run at less than the optimum linear velocity, in which case you might be better off with a longer column packed with larger particles. Basically, you have to juggle the tradeoffs among particle size, column length, flow rate, run time, and pressure.

[firework1]

thanks a lot