Chromatography Forum

I've always had problems with the 525.2 SPE. Hexachlorocyclopentadiene is the most difficult. It's always low...50% if I'm lucky. The remaining compounds are high and low. If I extract a few standards and use those to calibrate, I can get it all to pass. I've tried slower flow rates, different cartridges, etc. What are the best cartridges for this application? Any other suggestions??

Well, I might be biased, but I think that my cartridge is the best. The problem with this compound is that it is highly reactive. Avoid sunlight and conditions that would promote hydrolysis. Also use the best injection port liner on the market and keep your inlet clean. Acetate powder build up from ethyl acetate can act as an active site in your system. If you are careful, you should see recoveries of greater than 60%.

Don

Your cartridge is the best? What is it? I've used several. All c18, 1 gram. I understand that it's highly reactive. I test for it by EPA625 as well. My problem is not in the analysis, it's somewhere in the prep process. I've spiked the solvent in the turbovap...no problems there. How about a cartridge that has more than 1 gram of C 18? It appears to me that the cartridge is either not retaining the compound, or it's not completely eluting. Per method EPA 525.2, I have to have 70-130% recovery, so 60% doesn't cut it.

I'm the Enviro-Clean product manager for UCT. The C18 cartridge that I developed is product ECUNI525. It was beta tested at Lancaster Laboratories. The hexachlorocyclopentadiene recoveries ranged from 83 - 92%.

Don

Thanks. I actually ordered a batch of those the other day. Do you have any other certain tips for this extraction method? We use the Supelco vacuum manifold system. It can be tricky sometimes keeping the flow rates consistent for all the ports that are being used at the same time. Flow rates don't seem to be too critical as long as they stay between 10-20 ml/min. We pretty much follow what the method specifies in terms of cartridge conditioning, pH adjustments, etc. I only analyze the regulated compounds. I use the Accustandard 525.2 regulated mix in ethyl acetate. A mid-level spike takes 50uL of the diluted standard. Maybe I should have it diluted in methanol rather then E.A?

Yes, just follow the method. Your matrix spikes should be in a water soluble solvent such as methanol. As long as you have extract evaporation under control, a dim room and a clean GC system, you should be okay.