Chromatography Forum

I have a trace ultra gC which has been unused fro more than one year. The TR-225 column was not taken away from the GC although the GC had been off during this long period of time, (meaning it had stayed connected in the GC).

First thing i have to do is column conditioning.

I know the following steps should be followed:

1. Turn on the carrier gas and check there is a good flow. This was tested by dipping the detector end into
some methanol and checking for bubbles.
2. Allow the column to purge for twenty minutes to expel any oxygen that has entered the column.
3. Heat the column from 50 °C to the maximum temperature (230 C) at 5 °C/minute and hold for 1 hour.

Now i have the following questions:

1. What should be the flow of N2 carrier gas and temperature on the inlet? (Should there be any temp on the inlet?)
2. Should i disconnect the column end from the FID detector?
3. Should the detector be 'Flame On' during this time and its gases flowing in it or should it be OFF. the manual says the following but it is confusing me: ''If using a non-MS detector monitor the baseline during this time. If the baseline is still gradually falling after 1 hour consider extending the hold until a stable baseline is achieved. If using longer columns (> 30 m) or with thicker stationary phases (> 0.5 µm) conditioning may take longer due to the increased amount of stationary phase present'' <--- DOES this mean that the column should be connected to the detector?

Many thanks in advance.

Now i have the following questions:

1. What should be the flow of N2 carrier gas and temperature on the inlet? (Should there be any temp on the inlet?)
2. Should i disconnect the column end from the FID detector?
3. Should the detector be 'Flame On' during this time and its gases flowing in it or should it be OFF. the manual says the following but it is confusing me: ''If using a non-MS detector monitor the baseline during this time. If the baseline is still gradually falling after 1 hour consider extending the hold until a stable baseline is achieved. If using longer columns (> 30 m) or with thicker stationary phases (> 0.5 µm) conditioning may take longer due to the increased amount of stationary phase present'' <--- DOES this mean that the column should be connected to the detector?

Many thanks in advance.

1. I would set the flow to something like 1mL/min with your column type. What type of inlet do you have? If COC or PTV, I would choose track oven. If S/SL, I would choose the final temp of your oven program.
2. Yes! Unless you want the chance of plugging your FID jet.
3. The flame will not stay on if the column isn't installed. Don't worry about the FID while conditioning the column.

The injector is S/SL. The column is 60 m x 25 mm x 25 um.

If the FID is off how would the basline appear then on the pc?

What I would do is to disconnect the column from the detector, programme the column to to its maximum temperature at 2C/min, and hold for 1 hr. Have the inlet at its normal working temperature (with a clean liner and new septum, with the split at about 30:1). Then cool the column down, connect to the detector and programme up again while monitoring the baseline.

Peter

I'm thinking to take off 10 cm from both the beginning and bottom of the column before conditioning it, since it has been used for such a long time, although not more than 30 analysis have taken place more than one years ago.

If it were me I would run carrier through the column for a minimum of 1 hour before heating.

Why is that? Because the column is 60 m long?

It shouldn't take that long to purge air from the column. WHen I hook up a column to my GC/MS (quickswap so no vacuum) I can see the air come out and reduce the MS vacuum about 5 fold for a minute at most before it returns to normal vacuum and any air that remains probably isn't any more than you get from a headspace injection.

An important thing that we do not know is how much air got into the supply lines and GC plumbing during the shutown. If the GC is on a carrier gas supply that other instruments have been using in the meantime there is probably no air in the lines, possibly some in the plumbing. If the GC is on its own supply, and the cylinder was shut off, or even worse disconnected, then the lines might be full of air, and purging them out might be a wise precaution. That is most easily done by setting a very large split ratio and letting it run with everything cold.

Peter

Indeed I had a water trap where the gasket failed and I had to do some replumbing and it took almost a day to purge the lines of air.