in general: use the same material for the precolumn as the analytical column. otherwise you can get very strange effects. Frits (i do no know the phenomenex quard you mention) can be used as they show no retention but needs to be replaced regulary. About the waters guard: they sometimes show leakage, this is manufacturing problem, not yours. Try to see if that is the issue here.

in general: use the same material for the precolumn as the analytical column. otherwise you can get very strange effects. Frits (i do no know the phenomenex quard you mention) can be used as they show no retention but needs to be replaced regulary. About the waters guard: they sometimes show leakage, this is manufacturing problem, not yours. Try to see if that is the issue here.

I agree with Ed, you must use the same type guard column of your analytical column. You could try replace the guard column cartridge. Use the tools in the guard column kit to screw hard the male and female kit parts.

Hope this helps.

i had problems with something similar, i had to change to a Waters guard columns, because Phenomenex does not fit properly on Waters columns or Waters columns do not fit properly with the other brands... so is better for you to change before you damage the column if you continue screw it harder... Besides i remembered i had troubles even with a Phenomenex column and the same guard... i hope you solve the problem...

This product is supposed to have a fingertight fitting at the column inlet end with a variable length tube. Waters brand columns use an unusually deep fitting depth (unlike every other vendor) so usually require that you swage the fitting with the tubing bottomed out (dead-ended) to this very long length for a correct connection (a common cause for leaks on swaged lines). However, Phenomenex describes this holder as "Universal" and having a fingertight connection with a long tube extending out of the guard column holder to firmly seated at the base of even a Waters column inlet. If they are correct, it should only require normal hand tightening to create a leak free seal. Based on this concept, here are few things that could cause a leak at the Guard Column Holder: (1) Perhaps the holder was not fitted with the correctly sized column ID cartridge (you did not say which cartridge you installed inside it and they make different kinds for different column ID's); (2) Perhaps the holder was not sealed/closed up properly; (3) the variable length of tubing which extends out of the holder and fits into the column inlet may be stuck or damaged. It needs to very tightly fit all the way into the column inlet to work. This could cause a leak due to it not fitting tight against the column end fitting correctly.

Final comments:

Please do not waste your time and money on these guard columns. Just another part to troubleshoot and extra expense. Instead, use good chromatography techniques. Maintain your instrument by performing regular inspections and service as required to insure accurate results. Clean and wash each column after every analysis and flush the system at the end of each day to remove any salts or additives. Filter all samples before placing in the HPLC system. Make sure samples are fully soluble in the mobile phase. Label columns and test them upon receipt for quality using your own methods (not the one provided by the manufacturer which is usually very poor). *These types of procedures will insure that your system operates efficiently for many years.

In many applications, guard columns are really just a cheat for not properly cleaning the column or allowing too much particulate matter to enter the system due to a lack of filtering or poor sample prep.

I generally agree with Bill on his suggestions. The guard columns, or frit cartridges for that matter, are an additional trap for any particles. However, with good laboratory practice, there shouldn't be any insoluble particles in the system. Having said that, over the years I've used exactly those Phenomenex guard columns on various HPLC columns without any issue. 

Depending on the solvent volume throughput though, it is not unlikely that you will introduce some particles onto the front end of your column over the years. For instance when operating with preparative scale flowrates (10 - 20 mL/min), you will push through many liters of solvents every day. Even if it's just contamination due to airborne particles, or microplastic particles from e.g. old lids, etc., you can extend the lifetime of your column by using such "guard columns" or cartridges.

Thank you all for the answers!

I also have the exact same problem with leaking between the male and female connection of the guard column cartridge for the PHENOMENEX KJ0-4282 Security Guard and I am using a Phenomenex column

Save yourself the time and be sure to do proper sample prep before injection. No need for a "guard" filter for most applications at all (see earlier response).

with crude natural products that are mixtures of unknown compounds it can be difficult

With crude natural products, making sure the sample has fully dissolved in the mobile phase before filtering will save you hours of aggravation and plugged lines. A simple inline frit can be added after the injector and before the column inlet to protect against any large particulate matter. If you need more than that, then either a true "pre-column" (which is basically a short version of the analysis column, not a "guard column") should be used or better sample prep techniques should be used.