Chromatography Forum

Hello, I have an Archon autosampler attached to an OI 4660 purge and trap unit. When I run a water sample, everything works fine, I get 40 mL/min purge flow and great recovery. However, when I try to analyze a soil sample from the Archon, the 4660 immediately over pressurizes (above 30 PSI) when it goes into purge mode. I'm thinking there might be a valve that is no longer working on the Archon that is causing this issue. I was wondering if anybody else has encountered this issue.

It appears the system pressure is set too high in the OI-4660 Eclipse (30psi>). Then, when the Archon purges a soil, the 4660 purge flow is stopped/blocked via the Archon purge cutoff valve resulting in the over-pressure scenario.
The system pressure in the 4660 should be set at ~20 psi to prevent over pressurizing during an Archon soil purge. To set the system pressure; step the Eclipse to purge mode, cap/plug the vent bulk head, allow it to purge until the pressure stops increasing (max.) and adjust the pressure regulator accordingly. Note: in the event the system pressure is above 20 psi, relieve pressure (loosen cap/plug), turn down the pressure regulator, and repeat the process

Hope this helps.
Rick

Hi Rick - good to see you on this board. I think you have pacerlaser's issue handled well. (Pacer - EST is an excellent resource).

I would like to ask another question - We have a 4660/Archon setup as well. The sparge tube is only rinse/draining completely when we turn the purge gas off during bake. The auto drain after purge works correctly, though a little slow. It is when the Archon syringe rinses the sparge tube with 5mL that we have a problem. Any ideas?

Thanks, Tim

Hi Rick - good to see you on this board. I think you have pacerlaser's issue handled well. (Pacer - EST is an excellent resource).

I would like to ask another question - We have a 4660/Archon setup as well. The sparge tube is only rinse/draining completely when we turn the purge gas off during bake. The auto drain after purge works correctly, though a little slow. It is when the Archon syringe rinses the sparge tube with 5mL that we have a problem. Any ideas?

Thanks, Tim

Tim,

Does the 4660 pass a leak check? If the concentrator is leaking around the glassware, it will definitely affect the ability to push sample out the Archon drain. Also, if you disable purge gas during bake you essentially turn your sparge tube into a closed system. Usually, the Archon will struggle to push the rinse water into the sparge tube because there's nowhere for the additional gas volume to be pushed out with the purge gas disabled in the tube. The only way I can think that the Archon would push the rinse into the sparge tube in this scenario is if there is a leak somewhere. It's possible the leak is around the sparge tube, or it could even be the 3-way valve, or it's even possible some of the rinse water is being pushed straight out the Archon waste line (via a waste Burkert valve that is leaking across ports).

As to why it's not draining - usually it's a leak that causes you not to build up enough sparge tube pressure, or a restriction somewhere in the drain pathway (sparge needle, 3-way valve, transfer line, concentrator Burkert of Archon, waste Burkert of Archon, waste line of Archon).

For optimal performance, I would recommend using your purge gas during bake in order to use Archon rinses. If it is not draining with that feature on, you can try increasing your bake flow or actually increasing your 4660 system pressure to try to help improve the pressure in the sparge tube. Also, make sure your sparge tube needle doesn't have any cracks/holes in it, and make sure the tip of the needle is not directly on the frit of the glassware (make sure there's room for the liquid to come up through the tip of the sample needle).

Hopefully something in there can help.

-Mike

Just an update Mike - the problem turned out to be a pinhole in the sparge needle. Thanks for your help.