Chromatography Forum

This is Avinash, working as a senior executive in quality control department.

I have one doubt regarding Internal Diameter of tubing.

My doubt – What is the Internal Diameter of PEEK tubing I have to use to connect the column to the HPLC (Waters e2695)?
What is the Internal Diameter of PEEK tubing I have to use to connect the column to the guard column?

If we have to use only some specific internal diameter, why is it so?

Generally speaking, the narrower, the better.

For "conventional" HPLC systems, this will be either 0.007" or 0.005" id (for reference, 0.010" = 0.25 mm). For "UHPLC" systems, this will be either 0.005" or 0.0025".

The reason is to limit "extra-column" broadening of the peaks, which can happen if narrow peaks come out of the column into excessively wide tubing.

thanks for giving me the reply.

i have another doubt -
The ID of SS tubing to which we connect column is 0.009" (in Waters e2695 system), when we connect a PEEK tubing of 0.005" ID (less to that of SS tubing ID) does it create any abnormal pressure ??

Can't we connect a PEEK tubing of same ID as that of SS Tubing.

or Is it like irrespective of ID of SS tubing (to which we connect column), we have to connect only PEEK tubing of less ID???

Yes you can use the same ID PEEK tubing instead of SS tubing.
Using smaller ID tubings cause a little more back pressure , and may be clogged more easily.

SS tubings are more robust and compatible with all solvents , also withstand more pressure.
PEEK tubings are not compatible with Tetrahydrofuran for long term use.

If you are using mostly 4 or 4.6mm ID columns , use 0.25mm ID ( 0.01'' ID ) tubing for problem free operation.

And keep the tubing short!
Guard column can be connected to analytical column with a direct connector, or use inbuilt guard column system.

Most of the suppliers give tables of suggested diameters for different flow-rates; I know Phenomex do, and curently recommend 0.005 inch tube for columns 1mm diameter, running at flow rates of 20-100uL/min, and 0.007 inch for columns 2-4.6mm diameter running at flow rates of 200-2000uL/min.