LC Pre-Column Filters

When budgets are tight, we know that analysts are interested in making their LC columns last as long as they can.  There are many factors that contribute to shortening the lifetime of a column, but particulates are at the top of the list. We know that guard cartridges can protect an analytical column from particulates as well as chemical damage.  However, not all applications involve samples that need protection from chemical damage, but the threat of damage from particulates always exists. In cases like these, an inline filter can help ensure the longest lifetime for your column.

Since it is important to choose the filter that fits the pressure range of your application, I have divided our pre-column filters into two groups.

The first group of filters we will discuss are for LC systems that are rated up to 400 or 600 bar.

Our High-Pressure Frit-type In-Line Filter is our catalog number 25041, which comes with a 2 um porosity frit, which has a 4.0 mm through-hole to go with columns that are 4.0 -4.6 mm ID.  These frits are our catalog number 25022

The frits are actually what we call “cap frit filters”. They might look familiar to some of you because they are the same cap frits that we use with guard cartridges and the Trident guard holders. Not only can you purchase replacements for the 2 um frit as catalog number 25022, you can purchase frits that have a porosity of 0.5 um instead. You also have the option of purchasing frits with a 2.0 m through-hole, which would be used with analytical columns that have a 2.0- 3.2 mm ID.

Catalog number 25041 is connected to LC tubing on either side, placed in the flow path upstream of the analytical column.  It can be used with either PEEK or stainless steel tubing, but most analysts find the PEEK tubing easier to work with. This filter can be used with any of the typical 10-32 LC fittings, which includes stainless steel fittings, EXP/EXP2 fittings or PEEK fittings. The most simple and economical fittings to use for this application are our Universal PEEK connectors, catalog numbers 25015 and 27710.

The second type of filter that is used for lower pressure LC systems is the Trident Pre-column filter, our catalog number 27470 (or 27471 for a 4-pack). These are part of a group of products that we call the Trident LC Column Protection System, which also includes holders for guard cartridges that are used with our legacy LC columns (Ultra, Allure, Pinnacle and Viva). This type of filter is connected directly to the column inlet to minimize dead volume. Catalog 27470/27471 comes with a 2 um porosity, 4 mm through-hole, cap frit installed). These are the same cap frit filters discussed above that are used with catalog number 25041.

The 2^nd group of filters we will discuss are for UHPLC systems that are rated up to 15,000 psi (1034 bar).

The UltraLine UHPLC in-line filter, catalog number 24993, is connected to stainless steel LC tubing on either side, placed in the flow path upstream of the analytical column. The filter accepts regular 10-32 LC fitting threads, which includes several types of connectors we sell, including standard stainless steel fittings like catalog number 26537, 27727, 27728 and also our EXP and EXP2 fittings, such as 25926, 25937, 25940 and 25783 . This filter comes with a 0.5 um stainless steel frit, which can be replaced by ordering as catalog number 24994.

The second type of filter that is used for UHPLC is the UltraShield PreColumn Filter. This filter is available with 0.5 um stainless steel frits (catalog numbers 24995-24997) or 0.2 um stainless steel frits (catalog numbers 25809-25811).  The filter housing and frits are made to be disposable together as a unit. When it is time to replace, it is easy to start with a new filter and there is nothing to assemble. Similar to the Trident filter discussed previously, it is connected directly to the column inlet to minimize dead volume.

So there you have it- our options for in-line filtration at all pressure ranges. I hope you found this helpful and thanks for reading this blog post.

Please see below for additional resources, if needed.

Restek Videos

Preventing LC Column Clogs

Do I need an LC Guard Column?

Restek Blog posts

The Clog Blog

Is my LC instrument generating high pressure by itself?

Live Long and Prosper- How to make our HPLC columns last longer

Choosing a guard cartridge holder for LC

What’s new with LC fittings?

From LCGC North America 12-01-2014, Volume 32, Issue 12, Pages: 916–920

Column Protection: Three Easy Steps