HPLC Pump pressure increases wth blockage in guard column

[sboopathi]

As mentioned above, I used TSK Amide-80 column with its guard column. The pump pressure has been doubled since the last two experiments. I removed the gaurd column and checked the pressure and it was found to be normal. I did backflushing the guard column, but it didnt work and still the pressure is high. Is there anyother way to get rid of the blockage in the guard column. More than 150 injections have been made in the last one year since the gaurd column was fitted. Please suggest me some ideas...

[skunked_once]

The guard column was doing it's job, protecting the analytical column from being plugged. Have you tried replacing the cartridge in the guard column? It is meant to be replaced when it gets plugged. Another possibility is that the frit on the guard column is partially plugged with sample material. You did the correct thing by backflushing but that doesn't always work. If the frit is plugged, your options are to replace the frit or replace the guard cartridge holder.

[sboopathi]

Thanks Tom for your reply. I can identify that the blockage is in the guard column, but I dont know exactly whether the guard cartridge or the frit got plugged with the sample material. So replacing either one of them may not solve the problem completely if the plug is on the other side.

[lmh]

seriously, just replace the guard and don't even think about it, unless you have reason to believe that a single sample caused all the trouble (in which case think about it just enough to remember never to run samples like that again!).

Guard columns are supposed to be replaced. That's the point of them. If you divide the cost of the guard by the number of injections it has survived, you should have a very low cost per injection. You can easily waste more money in your time trying to clean the old guard than the guard is worth. If the guard is ridiculously expensive, start buying guards from another source; there are plenty of cheap but effective approaches to guards out there. For general physical crud (as opposed to chemical-crud that binds to the column), even just a filter is very effective.

Good luck!