Chromatography Forum

I have an Archon autosampler. There is no gas flowing through the soil needle.
Instrument works fine with water samples. Any Ideas?

When did it work last?

I have an Archon autosampler. There is no gas flowing through the soil needle.
Instrument works fine with water samples. Any Ideas?

If solids from samples become drawn back into the bottom holes in the needle it can become clogged. We had some samples that would quickly plug these holes and stop purge flow on the soil probe. We made an adapter to attach the helium purge line of the needle to the outlet of an HPLC pump and using high pressure could flush the needle out. It was the only way we could find to remove that sample residue.

For less difficult plugs, you can attach a disposable syringe to the helium line of the needle and force some methanol through it to unplug it. Otherwise you have to replace the needle once it is clogged.

I know its late to respond to this. This has happened to me a few times usually when doing soils that have very find sand or clay mixes. I alternate ultrasonication with pushing water with a syringe or 20-30 psi inert gas. If you can get it to leak even a bit, further sonication has shaken it loose for me.

I usually weigh smaller aliquots of soil (1-2g rather than 3-5g) if I suspect there will be a grain size problem.