Chromatography Forum

The tube that the column slides through it attached to the end of the bellows that has the column nut on it, so the tube(with tip) and column both move together as the bellows contract. The gold fitting that screws into the side of the analyzer will limit the in travel of the tip so it will always position the tip correctly inside the source.

Under vacuum the bellows allow the tip to make firm contact with the gold fitting which is how the source is heated on the 71/72, indirectly by the transfer line.

Hmm, interesting. I'd never actually thought about the tip being in contact with the gold cup, but it makes sense. I had ASSUMED that the analyzer was heated by radiant heating, but conduction makes more sense.

Still, though, that makes the straight-through tip in my mind even more logical since the path from the standard side-exit tip to the source is going to be even more convoluted. I do know that all the standard tips I've seen are gold plated, while the SIS tip I had wasn't. Analyzer temp is one of those parameters I always kept in the logbook(at least on the 71/72-I figured no point on the 75 since it holds its setpoint), and with the transfer line at 280º, ~165º was normal for my analyzer with either tip installed. I do remember when Geoff and I talked about the GCD he gave me, he mentioned that the analyzer tends to run cooler-maybe ~120º or so-on it than on a 71/72. That's still sitting in my office at U of L-I need to grab it before someone decides its junk(I robbed the sync cable off it to get the G1512A working with G1701BA, but that's not an impossible thing to find).

The tube that the column slides through it attached to the end of the bellows that has the column nut on it, so the tube(with tip) and column both move together as the bellows contract. The gold fitting that screws into the side of the analyzer will limit the in travel of the tip so it will always position the tip correctly inside the source.

Under vacuum the bellows allow the tip to make firm contact with the gold fitting which is how the source is heated on the 71/72, indirectly by the transfer line.

Doh! I did not realize the tube was rigid but now that you point it out it I see it. Besides how else to conduct the heat to the source? Before I start the foreline pump I move the topboard back and forth to get the transfer line standing out at a right angle and I try to center the top in the bucket in the perpendicular direction also. After I start the vacuum pump, I take a wrench and gently push the end inside the GC towards the MS source and feel for best contact.