I've come exactly to the same conclusion. The memory is strongly
associated with the syringe.
My work-around is similar to yours but for the solvent. I use CCl4
instead of Et2O. Call me old fashioned, but having witnessed several
Et2O accidents in my time, I'm not so keen on the idea of having Et2O
anywhere other than a ventilated solvent cabinet or a fume hood.
Anyhow, CCl4 forms an azeotrope with water at 95.9% : 4.1%,
respectively, which boils at 66 C.
Unfortunately, I haven't got the comforts of either a Combi-PAL or a
house vacuum line (conveniently located or otherwise). Going for the
systematic approach, I optimised wash cycles and post-injection delay
times on my A200S using a Hamilton 1.2ul syringe.
I could provide you with a few observation on how to destruct a syringe
together with a few choice additions to the dictionary of very
Seriously though, as long as I'm running samples I don't seem to have
problems irrespective of sample numbers. However, the syringe plunger
tends to jam if left to long to its own devices between batch runs. I
also noted a brown to greyish residue in the barrel of the syringe
despite running only bona fide clean ground, rain and spring waters.
I now dismount the syringe after a batch run and wash it extensively
with MeOH, "lubricating" it with a few drops of dry CCl4 before I mount
it again shortly before the next batch run.
Since this subject came up several times now on the list, I've started
writing up my observations (including furnace packing) in a method paper
for RCM. Watch this space.
NB: Will you come to the next SIMSUG? Loved the presentation you gave in