Chromatography Forum

Our lab plans to get rid of the old Soxhlet for solid. However, I know there are two technologies, microwave extraction and accelerated solvent extraction, to handle solid (soil, fish tissue). It is hard to decide which to go. Which one is better? Or Pro/Con for each technology?

We focus on semi-volatile, pesticides, occasionally petroleum hydrocarbon.

Thank a lot!

I don't have any experience with microwave extraction, but we did buy 2 used ASE 200s last year due to a large increase in our sample load. When they work, it beats soxhlet for time and solvent use, but we spend alot of time repairing valves and clogged lines. Also not impressed with Dionex's tech support and user's manual, we end up guessing where the problem is. They may have fixed these issues with their new unit, but can't get an answer from the sales rep either.
Preparing the samples is the hard part with this unit, you can't just mix it with sodium sulfate and go, it requires careful mixing with diatomateous earth and packing into the cell.
I hope another company comes up with a version of this technology, Dionex charges a premium for their monopoly, although some of the accessories can be found through Restek or Environmental Express.

Also, Envrionmental Express has a version of the proven Hot Block for use with organic solvent instead of microwaves. http://www.envexp.com/products/4-Organi ... Extraction
Unfortunately, it is not specifically addressed in EPA methods, so there may be a problem with accreditation.

Keep on Preppin'!

I have had the same experience with the ASEs. They do a great job, but the operators really have to stay on top of them to avoid problems. I have seen them routinely used at three labs; only one of the labs used it effectively. They work well, but they are easily broken. Folks try to cut corners using sodium sulfate; wet samples and acetone will drop the sodium sulfate out of solution once the extract leaves the pressurized vessel. The ASE tends to turn into a boat anchor after that.

I am not sure what has happened with Dionex, the support just seems to be gone - did they get swallowed up by Thermo?

I believe the ASE was originally purposed for SFC when that looked like a hot technology - it seems it never panned out so they managed to turn it into a fast soxhlet, essentially.

Funny, I've had great experience with Dionex Support. It's all under Thermo Fisher now, at least for the ASE 100 and 200 models anyway, for Ireland and UK. Once you disperse your samples properly and include some last-minute checks (double cell filtering for manky samples etc), ASE is a brilliant and quick replacement for Soxhlet.

Drying samples is definitely a con though, as mentioned Sodium Sulfate wreaks havoc with them.