Chromatography Forum

I run EPA 525 and recently have had lots of recovery problems. I have re built my GC/MS system and had my auto extractor re built as well. My recoveries are now acceptable for everything with the exception of hexachlorocyclopentadiene. I do not believe that I am "blowing" it away during the concentration step. I have spiked directly into solvent and then blown down in my Turbovap and get about 100% hexachlorocyclopentadiene recovery. In my mind this tells me that the loss is not during concentration.
I have tried different SPE extraction cartridge lots with the same results.
I have gotten subtle hints that it may be related to my DI water, as tests run on tap water give about 73% recovery vs 50% in DI.

I can't seem to think of anything else to try, and getting lots of pressure from management to get back into production!

Thanks in advance

John

You are not telling us some differences in handling of the spiked samples versus the samples in tap or DI water?

I have the same problem:(
I got only 20% recovery when I passed the sample very fast, say around 100 ml/min, now i slow down to about 10 ml/ml, but still get only 40-50% recovery. Do you use high quality solvent, do you muffle sodium sulfate or rinse it with solvent?
I'll try use pesticide grade EtOAc instead of HPLC grade and will update next week.

Do you have a carbon filter on the DI water? It may be bleeding thorugh organics on you? DI water systems are great for removing ionic contaminants - as demonstrate3d by conductivity. Reduction of organic contaminants is at best assumed unless you have a system that will oxidized organics with A UV lamp or such.

Try using some comercially prepared water that has known low ion condentration and known low organic background.

For the rest of the story! Up until July of this year everything was fine for hexachlorocyclopentadiene. Now everything I do is to no avail. I did spikes of Di, purchased water ( no information as to how old it was) , and well water. I saw no significant differences!!

Im now wondering if there could be anything "growing" in my Autotrace pumps, as they are not addressed durring a PM ( which I have just had done).

I push sample through my cartriges at 30 ml/min and have always used this flow rate.

Is there anything changed since July? such as solvent, reagent, glass vials?

For the rest of the story! Up until July of this year everything was fine for hexachlorocyclopentadiene. Now everything I do is to no avail. I did spikes of Di, purchased water ( no information as to how old it was) , and well water. I saw no significant differences!!

Im now wondering if there could be anything "growing" in my Autotrace pumps, as they are not addressed durring a PM ( which I have just had done).

I push sample through my cartriges at 30 ml/min and have always used this flow rate.

Hexachlorocyclopentadiene is highly photosensitive. We had similar recovery problems using liquid-liquid extractions for this compound--often in the 8-10% recovery range. Our extraction lab had many windows and we were getting a lot of UV exposure it turns out. I tin-foiled all of the external windows, the view-port on the hood, and we keep lights totally off at night.

Recovery for this compound bounced right up on par with other analytes.

Good luck!

An update. I was able to procure a diagnostic disk for my autoextractor.
Running it I find all ia not well with it. Durring the drying step there is lots of flow through the cartriges. I'm betting that's where my hexachlorocyclopentadiene is going. I'm waiting for factory service.

Thanks, it works.
I covered the hood where I do SPE and the hexachlorocyclopentadiene recovery increased to around 75%.

Hexachlorocyclopentadiene is highly photosensitive. We had similar recovery problems using liquid-liquid extractions for this compound--often in the 8-10% recovery range. Our extraction lab had many windows and we were getting a lot of UV exposure it turns out. I tin-foiled all of the external windows, the view-port on the hood, and we keep lights totally off at night.

Recovery for this compound bounced right up on par with other analytes.

Good luck!