Chromatography Forum

Hello all,

On a 60m RTX 1 0.32 ID with 1micron film, we have injected 1uL of sample at 30:1 split, with high amounts of water (20-50%wt) and para toluene sulfonic acid at 2%wt about 200-300 times. I am now seeing badly tailing peaks when analyzing a mixture of THF and alcohols (ethanol, propanol, butanol). The THF peak is symmetrical, sharp and has similar area counts to past retains and QC checks. The alcohols are showing much less peak areas and are tailing badly.

So far I have changed out inlet liner, seals, cut about half meter off the front column. Same results. I am wondering if the pTSA or pTSA water mix has damaged the column?

Thanks,

What's your detector?

Given that you have 60 meters of column and trimming the first half meter hasn't made a difference, try chopping 1-2 meters and seeing if there's any improvement.

Happen to have handy any other standards (solvents, etc.) that you've run previously as yet another check?

Which liner are you using, and when you say you've swapped them out, is it precisely the same liner as that which you originally got good signal?

I have run different standards with various compounds and it seems to only be those three alcohols which tail and run into other peaks.

Its an FID, which I took apart yesterday and cleaned. It was very clean, one of the ceramic discs had some particulate on it which I cleaned off. I did notice that there was some very minor white scale next to the Nitrogen makeup inlet in the housing. I am wondering if that is from moisture in the nitrogen stream. But I have 5 other GCs using the same gas and they are not having issues.

From the manufacturer's website samples with pH less than 4 will damage the column and I'm sure that material was at pH 2 or less.

I am installing a new column today, if you don't hear back then that was the issue!

And yes, same 4mm straight Split liner with wool.

From the manufacturer's website samples with pH less than 4 will damage the column and I'm sure that material was at pH 2 or less.

I am installing a new column today, if you don't hear back then that was the issue!

The pH thing sounds pretty culpatory. Keep your old column, and consider using pieces of it as a guard column for your new column.