Chromatography Forum

I have a Luna C18(2) column that has worked beautifully through about 3 months of heavy use ~ 30 hrs/wk, but recently, the backpressure is ~20 bar higher than normal and many of the peaks have a shoulder on the front side. At first, I assumed that I was just injecting too much sample, but the shoulder was still there at 1/2 and 1/4 the sample concentration. I thought it might have been a void space or clog in the guard column that caused this, but I tried running some of the same samples without a guard column and got the same results. Also I tried reverse-flow cleaning w/ 1:1 ACN/THF, and that had no effect. Is there anything else I can do that might fix my column? Thanks in advance,
Chris

Columns are a consumable. Time for a new one.

We have recovered a lot of our columns by opening the front of the column. Most of ours fail because there is a void. Usually we just slurry some C18 packing with a solvent then fill in the front of the column with the slurry using a spatula. Then put on a pump and let it flush for a while.

If a column is too bad, will scrape a small amount of the material from the front of the column and fill with the slurry.

Recovered many columns this way many times per column. One of the guys in the lab does it routinely in his spare time while doing other things. Amazing how well they work.

James,
I opened the thing up, sonciated the entrance frit in IPA and packed some C18 slurry into the top of the column, and surprisingly enough it works again! Thanks for the help!

Chris

I have a Luna C18(2) column that has worked beautifully through about 3 months of heavy use ~ 30 hrs/wk, but recently, the backpressure is ~20 bar higher than normal and many of the peaks have a shoulder on the front side. At first, I assumed that I was just injecting too much sample, but the shoulder was still there at 1/2 and 1/4 the sample concentration. I thought it might have been a void space or clog in the guard column that caused this, but I tried running some of the same samples without a guard column and got the same results. Also I tried reverse-flow cleaning w/ 1:1 ACN/THF, and that had no effect. Is there anything else I can do that might fix my column? Thanks in advance,
Chris

what is shoulder on the front side of the peak.

thanx for the reply in advance

regards

amaryl

amaryl,

I'm not sure if one can classify all observations as being due to the same root cause but in cases where shouldering is observed on all peaks in approximately the same manner (often shouldering is more evident on later eluting peaks), the cause of the problem is most likely multiple flow paths through the column bed (i.e. some sort of column bed damage), a partially plugged inlet frit or an uneven headspace at the top of the column. I usually try replacing the frit first as this is fairly straightforward to do. Usually, as in the case above the headspace problem can be remedied by filling in the void with some stationary phase scavenged from some available source. If neither of these approaches correct the problem, it's usually time to replace the column.