help,why my peak split?

[moon704520]

hi:

one column 50*250mmL was packed with C4,10-15u,300A silica,the column efficiency was oK tested with Nathphthalene and phenanthrene
after that the column was plugged and stored at the lab,but ,one mother later,I retested the column efficiency,to my great surprise,I find that all the testing probe splitted?why is so ?then ,I reverse the column ,all the peak is normal!any suggestion will be highly appreciated!thank you!

[Uwe Neue]

Column packing is an art. Packing fat columns is even more of an art. My suggestion would be to purchase such columns from a reputable manufacturer with experience with such things.

What happened is the following: the column was not packed to a sufficient density. Letting it sit for a while created a void on top of the column. Turning it around removed the void - for a while at least.


(I like your expression: one mother later... check your dictionary, and I am sure you will have fun as well)

[moon704520]

Dear Uwe Neue:

thank you very much for your useful suggestions!actually it is one month later I find something wrong with my column!and then I wet the column bed with 50%ACN/50%H2O after that I packed the column bed out of the column body!I found that the head of the column bed is relativly hard and the end of the column bed is very soft !and why is so ?is that because of the clogged frit or some other reason?you said the suficient packing density was not reached ! what I can do next?increase the packing pressure ?should I change the slurry solvent?(I use IPA)thank you very much!any advice will be welcomed!

[tom jupille]

As Uwe indicated, column packing is an art. Years ago, when I worked for a column manufacturer, for each new batch of packing material, we would pack six test columns, using different pressure/flow/time profiles in order to optimize the procedure for that batch.

The overwhelming majority of columns used today are manufacturer-packed. The details of their procedures are proprietary and there is no "one-size-fits-all" recipe. You will have to carry out successive approximations to find the best set of conditions for your particular packing and column dimensions.

[moon704520]

thank you ,tom,I get the point