Chromatography Forum

hello again,
i have some questions about tubing in the agilent/varian hplc;

i am an analytic chemist at pharmacy company; until now i was warking on varian hplc system; there were peek tubing connections 0.02 in (i.e. 0.5 mm?) just before and after column; the rest of connections were steel and, according to service (technical support), were not 0.02 in but 0.01 in.

since couple of weeks we have agilent 1200, and the connections are steel and 0.17 mm (0.007 in);

because I make analytical methods and validate them, it is very important to me that transfer of the methods fom agilent to varian was not problematical (I mean retention times of the peaks mainly, but shape and symmetry of the peaks is very important as well);

so I called the agilent service and asked what to do, thay suggested changing of all connection tubings to 0.02 in;

I was working couple of months ago with agilent 1100, and I do not really remember we changed all connection tubings; we changed only the tubings before and after column, but i do not remember if the change was so drastic ( I mean from 0.007 in. to 0.02 in.); I think that we change those tubings 0.007 in. to 0.01 in.; and i had never changed the rest of the tubing using agilent 1100;

when I asked varian service, they told me, that it is not really important to change all tubings to the same diameter

so now I am really confused about the situation; first of all what to do with the tubing connections to make method universal for varian and agilent hplc systems

the second thig is the diameters of tubings; is it true that they all need to be the same diameter; is it dangerous for hplc system to use different diameters of the tubings? can I damage the system using other diameter tubings only before and after the column?

For analytical work 0.5mm is far to large a diameter.

I see no need to change the Agilent tubing unless you are going to work at a very high flow rate

I would change the internal diameter of the tubing only if all your planned applications justify the change. I don't think I'd change a system to a larger internal diameter, as the whole system is presumably optimised for the configuration you purchased.

The tubing internal diameters would be important from mobile phase mixer ( for gradient operation ), to the detector. The flowrate ( backpressure ) and column ( particle size/diameter ) tend to define the appropriate tubing IDs and system volume. The tubing ID can be different in the system, but I'd again question why change the system.

I would suggest performing a few experiments to understand the characteristics of each of your HPLC systems - eg dwell volumes, internal volumes, backpressures etc., and choose equivalent columns for each system, rather than try to homogenise them.

If you want to change, Agilent sell a range of conversion kits for the 1100/1200 that use tubing of different IDs ( eg 0.17mm, and 0.12mm, and 0.10/0.05mm for the capillary LC ), and detector flow cells of different internal volumes, etc etc. I think the manual for each module describes the various options, according to the column and flowrates planned.

Bruce Hamilton

Unless you have very long tubing lengths on the Varian system, you should see no differences with the Agilent system. In fact, I would expect peak shape to be a little better.

But realize that anytime you move a method from one instrument brand to another brand, you are likely to see some differences. Certainly detector response will be different, but there can be changes in retention time and peak shape as well. If you are using a gradient separation, then expect some significant differences, due to differences in mixer designs.

I would never change to a larger tubing diameter, unless all other efforts have failed.