LLE for UPLC/TQD assay

[mtorrey]

I have given up getting a clean PFF for this Pentobarbital method I've working on and wonder if using a LLE extraction similar to what we use for our GCMS would harm the detector in anyway.

I basically mix the sample and internal standard in 1 mL 0.25M Ammonium Acetate and 4 mL Heptane:Ethyl Acetate:Acetone (80:15:05). I spin that down and take off the upper organic and dry it down completely. Then I reconstitue with 400 uL aqueas phase and shoot.

The reconstituted sample looks clear, column pressure remains stable +/- 10 psi and the chromatography looks great. But I wonder what kind of problems could arise months from now. I'm assuming as long as I completely dry down the organic phase I should be safe but you never know.

TIA

[Uwe Neue]

LLE is usually rather good for sample cleanup. Assuming that you are dealing with a plasma sample, your method will also enrich lipids and phospholipids. This may at some point in time give you shifts in retention / ion suppression. You can then flush the column, or throw the column away. If this happens much earlier than you would like, you need to go to SPE for sample prep.

[Bryan Evans]

You can also try direct injection on Cadenza HS-C18 (the serum
proteins are excluded from the column):

http://www.silvertonesciences.com/files/TI296E.pdf