Chromatography Forum

I have a 60-m 0.25-mm DB-5 column that is bleeding polyaromatics and heavy amines (probably due to its previous use) at 150-250oC. I already cut off 1 m length...

Is it possible or practical at all to extend its life by rinsing such a long and small-dia. column with a low-viscosity solvent (ether, hexane, methanol...)?

Column rinsing of bonded-phase capillaries can do a good job to restore performance. I just reverse-rinsed a Restek and an Agilent column Wednesday. I have an apparatus for this from either Restek or Agilent, makes it straightforward. I used CH2Cl2 to rinse.

But also take into consideration your time to set up, do the rinse, then dry out with inert gas. Of course, one doesn't sit there and watch it, but you must decide if it's worth it to your company and your supervisor.

If you don't know the column history, it can be difficult to remove the contaminants. Then the issue becomes " are those unwanted peaks from the column or the sample?".

As CPG notes, it really also depends on the value of the analysis and your time, and especially the sensitivity of the method and detector.

In general, it's better to use cleaned columns for research samples. If you have a QC or QA method that quickly gunks up columns, the method probably needs more work in the sample preparation step.

I've used an inexpensive SGE capillary washing/coating system that held about 10 mls, but I also made a simple column cleaning system by filling a vertical, empty, HPLC column with solvent, and used cylinder helium and a mass flow controller to slowly push it through a 50 metre 0.25 mm capillary overnight, once the liquid was through, the helium gas then dried the stationary phase. Worked OK for me, but the SGE system enabled the user to see the solvent level.

It's worth a try. Just remember to put the solvent through in the reverse direction to the GC carrier gas i.e. from the detector end.

Peter

I did it using a simple 2-mL GC crimp-top vial, a single GC inlet (if your instrument has spare time) and some washing solvent. What I did was installed a ~10-20cm capillary column to a GC inlet and peeled another column end thru the cap to the GC vial halfly filled with some wash solvent. Do not dip the end to the solvent. With the capillary column to be washed, peel thru the cap and dip the end into the solvent. Apply column head pressure until you see drops of solvent running out from the other end of the cap column. Be patient and it takes some time for the solvent to fill up the whole capillary. The setup costs almost nothing except you need to spare some time for one GC inlet.

Hubert

Thanks for all the replies and useful advice--apparently, it does make sense! (I wasn't sure about hydraulics... The instrument/column is used for exploratory research, not a highly regimented QC/QA process, so I'll give it a try.