column maximum flow

[tellest81]

there is someone who can help me to found the maximum flow or pressure of the Agilent Poroshell 120 EC-18. because someone say that it's depend of the maximum pressure of my HPLC system (the infinity 1260 LC system system). and i think that 600bars is a very high pressure for a chromatographic column. I never work with agilent system but i worked during 4 year with the waters HPLC system and column. someone can give me more information about this subject?

[tom jupille]

There is no simple answer. That said, usually you work it the other way around: you know what flow you want to use; the question is how much back pressure will that flow generate.

The pressure for a given volumetric flow rate will depend on:
- the column length (longer column = higher pressure)
- the square of the column diameter (wider column = lower pressure)
- the particle size (smaller particles = higher pressure)
- the viscosity of the solvent (higher viscosity = higher pressure)
- the temperature (higher temperature = lower viscosity = lower pressure)

http://en.wikipedia.org/wiki/Hagen%E2%8 ... e_equation
http://fr.wikipedia.org/wiki/%C3%89coul ... Poiseuille

[tellest81]

thanks tom!

yes! generally i use the optimum flow or i look for this optimum but this information is easy to found because company (agilent, Waters,...) give sometimes a flow optimum range in relationship with the solvent. i don't Know how they have this information but i suppose that they study the fluid mechanic (Hagen-Poiseuille equation). but i think that if you work everytime with a high flow, even if this flow allowed to a presssure wich is lower than your hplc system , this phenomen can resulted in a bad resolution of your elution. (sorry for my english!) and sometime when i make a column maintenance, i need to know what is the maximum flow of my column.

[tom jupille]

Don't worry about your English. Votre anglais est meilleur que mon français!

With small-particle packings (less than about 5 micrometers), the loss of efficiency at high flow is relatively minor (at least for small-molecule samples; proteins are a different story) so that using the "optimum" flow rate is usually not cost-effective; with a 3-micron packing you might gain 10-15% in resolution at a cost of 2x or 4x the run time. In our Advanced Method Development course, I usually suggest that the flow be set to whatever generates a back pressure of about 40% of the system maximum (so, about 150 bar on a system that can operate at 350 bar). That allows some margin for column aging (back pressure usually increases over the lifetime of a column). What that flow rate actually *is* depends on all of the parameters mentioned. Most people don't calculate this, but simply note the pressure at a given flow rate and adjust accordingly. Pressure is a linear function of flow, so it's an easy adjustment.

[tellest81]

Thanks a lot for your help!!!

[Consumer Products Guy]

Most people don't calculate this, but simply note the pressure at a given flow rate and adjust accordingly. Pressure is a linear function of flow, so it's an easy adjustment.

Yep, that's me.

I leave the equations to Tom J.

[mkumar75]

Dear User ,
The Pressure generated by column is toterated upto 600 Bar , that is only the packing of column which will not be disturbed during the usage in mentioned pressure.
As far HPLC or the machine is concerned , normal LC system that is Waters / Agilent they can tolerate the pressure upto 285bar ( approx. 4000 psi ) , or upto max 357 bar ( approx. 5000 psi ).
Further this much back pressure may damage to the seals in machine , which may lead to leakage and malfunctioning of machine .
My suggestion is to use the column or develop the method such that it should be having the column back pressure of NMT 3000 psi (214 bar ) in HPLC
If not possible for that method then choose UPLC.

Thanks....Manoj