Chromatography Forum

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?

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

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.

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.

Thanks a lot for your help!!!

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.

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