Chromatography Forum

Hi I am wondering if anyone had this problem .

I was fitting a new column it seemed okay and it was conditioning for aboiut an hour then all of a sudden the head pressure onm the column started to fall and then reached 0 .

There now is nothing coming from the split vent or the septum purge .

I was wondering if this might be a mechanical fault in the GC . Gas is gettign to the inlet pressure pump but it is not going anywhere from there . Also rather worryingly there does not seem to be an EPC board installed and everything I read leads back to thatbeing a problem .

If anyonme could help I would be most appreciatve

It sounds like you broke a column.

Find out where the gas is going and you will find the problem.

Since it started OK I assume you may have broken the column at the inlet.

If you heated the column with an exposure to air the column may be ruined.

Good luck.

Rod

It sounds like you broke a column.

Find out where the gas is going and you will find the problem.

Or you have a big leak. As Rod said "Find out where the gas is going and you will find the problem."

Now you would feel really silly (and I won't say it has never happened to me) if you simply forgot to turn the gas on at the regulator or your cylinder was empty.

How do I know to suggest this?

Read my parenthesis.

best wishes,

Rod

Beilive me the gas was the first thing I checked ( not saying that I have done this before) .

I know the gas is getting to the Mass flow controller but it is not going anywhere else after that, that I can see .

I did consider that it was a broken column after searching the web but when I changed the column it seemed to make no difference .....

Is there anything else I could check ?

Thanks

Adam

You may want to even check you septum and top nut. Sometimes, overtightening the nut at the septum or leading into the injector port can cause the pressure regulator to sense a problem and drop. Another place to check is the nut on the inside of the GC and the ferrule you are using. If you overtighten this, the ferrule, which is soft, can squeeze the column and crush the end leading into the inlet. Are you using and I connector or Y connector? One last place to check: if you opened the weldment assembly, the line leading into the inlet can be fragile...there is a small brace on it, but repeated opening and closing can cause a small leak, which can be compensated at first, but which will eventually break and cause a drop. Do you hae a leak detector? If not, you can cool the inlet and GC, keep the gas on, and try dropping a little solvent on the lines. If there's a leak, you'll see small bubbles. (However, if it's too hot, you'll see the solvent vaporize anyway, which you don't want to do...)

BedlamVR,

Put your finger over both the split vent line port and the septum purge port. Gas has nowhere to go now except column so head pressure should rise (assuming not a broken column.) If no pressure, increase the total flow control. If still no pressure, obviously, major leak. Unfortunately hard to troubleshoot in an HP system without a leak detector because you cannot isolate flow paths very easily. If you have a leak detector, plug both outputs and leak check all the fittings. Also, make sure you have the little o-rings on all of the gas lines as these are what make the seal.

Finally, I have seen very strange injector behaviour when the gas lines are connected incorrectly to the splitless/split valve so you want to verify this is correct.

Best regards.