Chromatography Forum

I have an old dodgy wax column with a big fat hump in the middle of my chromatogram. As a last resort to try and save it somebody suggested a solvent rinse with DCM or hexane. So I'm shoving a few mL few of each through the column.

Here's my question:

The DCM going in is clear and coming out it's yellow. Is the yellow my contaminants or my phase?

From back in the days of packed columns, I remember the wax phase as being colorless. So 1) the yellow is likely to be stuff you don't want in the column and 2) if the wax were washing off, you wouldn't know yet...

Good luck!

Fat Jonny,

Is it a bonded capillary or a dodgy old packed column? If packed the odds are much higher that it is not bonded and you could be washing off phase. Don is right, give it a go while you convince your management that you need a spare column for that instrument anyway.

Best regards.

Well I convinced the pointy haired boss I needed a spare column by the fact that my analyte retention changed from 12.5 mins to 2.5 mins after washing!

I guess I screwed that column..... The spare's on its way!

It is/was bonded.

You mean the replacement is on the way; hopefully you'll get a spare and keep that in the drawer for troubleshooting and elimination of downtime next time the column goes bad. Make sure he knows that columns are consumable items, and even more so for PEG-type columns.

Hey Fat Jonny,

Just tell your boss that you have developed a fast GC seperation.

Ha ha! That would be true if the peaks were narrower and I wasn't dealing with 29 analytes that were originally in 20 minutes and now in 4 mins!

Oh well, I have a replacement and a spare on the way

Here's a funny question I was asked by the suit people: "since a 60m column costs a lot less than two 30m columns, can't you just buy one 60m column and cut it in half"

cheapskates....

Here's a funny question I was asked by the suit people: "since a 60m column costs a lot less than two 30m columns, can't you just buy one 60m column and cut it in half"

I used to run an ultra-fast FAME analysis using a 5m 0.18 id column. I would make 4 of them out of a 20 meter column because the supplier didn't sell a 5 meter.

It generally works well, but column manufacturers qualify the entire length of the column before they ship and there may be sections with little or no phase. Sometimes I would cut a 5 meter section with not enough retention for the analysis.

You would probably would not have that problem with a 30 meter section of a 60 meter column. But it's a good excuse for the boss to avoid the hassle of having to re-wrap the column, chance of breaking it, contamination, etc. just to save a few bucks.