I have a bit of a problem. I'm doing cap-LC (50 micron i.d.) and while thats problematic in itself, my real issue is with packing uniformity. I've unpacked a Dionex PA-100 guard column and am attempting to pack my capillary. The particle size is supposed to be 8.5 microns. The problem is that I can only pack about 6 cm (many times less) before it clogs and I can pack no further. When i look at the column under the microscope i see either one or two very large particles somewhere in the middle of the column. These particles are much bigger than 8.5 um. A sonic dismembrator is used to break up particle aggregates before i start to pack. My real question is "if i purchase a full column, will the particles be more uniform than the guard column which seems to be a product of poor qc.
Any advice would be welcome
Thanks in advance
Jim

Jim,

I believe you are mistaken regarding your assessment of the cause of clogging. The material used to produce the CarboPac PA-100 is a latex agglomerated divinylbenzene-ethylvinyl benzene substrate. The process of packing this resin and the electrostatic nature of the attachment results in the production larger agglomerates during the packing process which are difficult to de-agglomerate unless you have a 1000 watt probe type ultrasonic device. A much better course of action is to use resin which hasn't previously been packed.

Chris,
You're absolutely right. After using resin that hadn't been packed all my problems went away. In fact my peaks look better also. I can now pack 20 cm in about 20 minutes rather than hours. Also you were right in that it appears that adding 0.50 mM KCl to the slurry makes them much happier. Thanks for all your help. You've saved me alot of time.