How do I Replace my LC Tubing?

For those that are experienced with LC, you probably have this all figured out.  If that is the case, this might serve as a good introduction to Restek products that you can use for this.  For those that are newbies to liquid chromatography, welcome and I hope you find this useful!

The best way to replace tubing in an LC system largely depends on where the tubing is located, how it is used and the material it is made from.  In all cases, tubing must be cut straight and square on the end to achieve a good seal.  This is even more critical when you are operating at higher pressure ranges.

PEEK (polyether ether ketone) tubing is used for lower pressure applications.  We recommend using PEEK tubing with ID of ≤0.007 inches for applications up to 7,000 psi and the tubing with an ID of ≥0.010 inches for applications that go up to 5,000 psi. These are color coded with a stripe so you can tell what the ID (internal diameter) is.  Here are the codes:

Clear= 0.0025”

Red= 0.005”

Yellow=0.007”

Blue= 0.010”

Orange= 0.020”

 

We suggest to use our Clean-Cut Tubing Cutter catalog #25069 to cut PEEK (and other plastic) tubing. Here’s what it looks like:

 

Stainless steel tubing can be used at just about any pressure range, including the higher ranges for UHPLC.  It is also considered more permanent, so most internal LC connections are usually stainless steel. Although most durable, stainless steel is harder to work with, in general.  I mentioned earlier that it is critical to have tubing cut straight and square on the ends to achieve a good seal.  This is very true with stainless steel, especially since it is used at higher pressure ranges.  It is also more difficult to ensure the tubing is smooth and very straight on the end, so for these reasons, we do not recommend for customers to cut their own stainless steel tubing for LC.  It is much better to order the tubing that is already professionally cut to the desired length.  We offer stainless steel tubing in pre-cut lengths of 5, 10, 20 and 30 cm and ID sizes ranging from 0.005” – 0.020”. We use the same color code for these as we do for the PEEK.  Instead of a stripe along the tubing, there is narrow band around the outside of the tubing.

 

While it is nice to have generic lengths of tubing available with no fittings attached, you may be looking for something more specific.  In some cases, you may need to obtain tubing with pre-swaged end fittings attached or you may be looking for specific dimensions to fit a certain location for replacement within your instrument.  Some instrument parts may also contain a specialized end fitting to serve a certain purpose that is specific for that instrument model.  This is why we often suggest that customers replace the entire tubing assembly that comes with the proper fittings, as specified by the instrument manufacturer.  The only reliable way to do this is to identify the manufacturer’s catalog or part number and seek a direct replacement for that.  Fortunately, for our customers using Agilent LC models, we do sell a few of the more popular tubing assemblies to fit Agilent LC models on our website. 

If you select an individual item from the link above on our website, you can see which Agilent part number the item corresponds to.  Feel free also to contact our Tech Services department to see if we have a replacement, if you know the part number and cannot find it.

To help confirm your selection, I have listed the primary location of usage and dimensions for each of these tubing assemblies in the table below.  Please note that some of these may be used for general purposes in other instrument models also, but the location I have specified here in the indicated model does require these particular dimensions.  Generally for most Agilent HPLCs, the tubing used in the system flowpath between the solvent module and the autosampler sample injection valve has an ID of 0.25 mm.  Likewise, the tubing downstream from the sample injection valve to the detector has an ID of 0.17 mm or smaller to minimize band spreading.

I hope you found this post helpful.  Thank you for reading!