I do EPA 525 with extraction cartriges and an Auto trace. My last two runs I loose about 50% endrin and hexachlorocyclopentadiene and about 100% terbacil for my LFB's amd LFM's.
I ran a set of MDL's before the problem arose using the same lot of cartriges I'm now using. The numbers are very good and the MDL is spiked at 1/10 that of the LFB/M's I run with samples. I ruled out the cartriges with this data.
The loss is not in my GC/MS.
I tested my Turbovap by spiking my solutions into solvent and blowing them down they looked like CCS's.
I then preped some CCS's and aloquoted them into collection vials used in the autotrace and stored them for 2 days. The result no losses.
My next test is to test my sodium sulfate drying step. I re use glass fritted cartriges and fill with muffled sulfate for every use.

Has anyone has this problem?

Thanks
Bear