Chromatography Forum

We have 6890N with 7694e and ALS. I'm decent with the ALS and GC, but completely new to headspace. For the headspace: vial 165, loop 180, line 190 - just going for relative residual solvent numbers on a 155 tg polymer. 7694e was bought unused from a 3rd party who ordered it then ended up not using it (or something). Looks new.

I set the temps on 7694e, but after a couple hours or so only the transfer line temp has increased at all - now about 100C. Is this normal? Should it take hours to reach temp and only heat the transfer line first? I checked the fuses and they look fine. This seems like it should be really easy. Set the temps, wait a bit, go. Not sure what could possibly be going wrong. Any recommendations? First time using the 7694e.

Also, if anyone knows/is/recommends a consultant on GC in the San Francisco area, it would be great just to have a person to call when this stuff pops up, and with method development and such. I've kind of learned GC the hard way over many years, but it's just a tiny piece of my responsibilities that sometimes gets hungry and starts devouring entirely too much time.

- Russ

It's definitely not normal, but the temperatures that you have set are very high for headspace and I wonder if you have not gone above some pre-set limit. Usually you should get an error message for that, but it is worth trying to set everything to say 80C to see what happens.

You might have bought a lemon of course, and getting it checked by a service engineer is the next step.

Peter

I agree with Peter. try lower temps. I thought you never wanted to "boil" your analytes using headspace.

Hmm, not encouraging. The temps are well within spec for the tool, and the method is borrowed from a test lab that did external analysis for us. Setting lower temps makes no difference in any event.

I'll check connectors and such, and the suggested troubleshooting actions from the manual, which mostly say "check these things and call service" and try to contact some kind of a service engineer.

- Russ

Wait, it looks like the unit is meant to be 240V. We've had it plugged into 120V and it doesn't give any error messages or anything, just doesn't heat. When we bought it, I realize now it didn't specify the power of the unit and didn't come with any cords - it came from Cleveland so we assumed it would be 120V.

I bet that's it. I'm leaning towards just ordering a step up transformer that's rated for > 600 W (listed power req. on back of 7694e) and being done with it. Does that sound reasonable?

Always something in a lab. Always something.

Wait, it looks like the unit is meant to be 240V. We've had it plugged into 120V and it doesn't give any error messages or anything, just doesn't heat. When we bought it, I realize now it didn't specify the power of the unit and didn't come with any cords - it came from Cleveland so we assumed it would be 120V.

I bet that's it. I'm leaning towards just ordering a step up transformer that's rated for > 600 W (listed power req. on back of 7694e) and being done with it. Does that sound reasonable?
Always something in a lab. Always something.

Yep. Hope your instrument will work properly with proper voltage.

Fixed.

In case anyone runs into an odd similar problem in the future - you can switch the voltage with a switch inside the back electrical panel and by swapping a total of 3 fuses. Heating normally now.

- Russ

Thanks for the feedback. At least plugging a 240V machine into 120V is less dramatic than the other way around.

Peter

haha.. I am using the same but not found any issue or something you all are talking about.

Glad to hear its fixed. I know on the 1888 HS they ship with 240 V selected on the switch on the rear of the instrument and if you don't switch it to match a 120 V supply it will take a very long time to heat up.

The transfer line for both of these models should heat up VERY quickly. The oven and loop may take a few minutes, but the transfer line should be at temp within 2-3 min.