Re: LC-MS instrumentation
Katheryn Resing (Katheryn.Resing@Colorado.EDU)
Thu, 14 May 1998 09:06:37 +0000
It sounds like ease of use is important to you. We have a sciex and we
have lots of biochemistry grad students using it. None of our users are
mass spectrometrists. I typically take 1 hr to train them and they can
then use it themselves with a little help from someone once in a while. The
interface is exceptionally easy to use. The macintosh software they
provide is very user friendly.
If you are going to do sequencing or analysis of in-gel digested
samples, you might also want to consider the Finnegan LCQ. Although the
interface is a little touchier and the software is harder to learn
(anything on an IBM can be frustrating), the MS(n) capability looks very
useful.
Whichever mass spectrometer you chose, a critical issue is the HPLC
(our students have more struggles with learning HPLC than with learning to
use the MS). Get an easy to use pump for them to work with (we have an ABI
syringe pump fitted with 10 mL syringes that has proven to be a real
workhorse; an HP on a different LC/MS system in our department has proven
harder for naive users and is more frequently down). Work with 500 micron
columns at 20 microliters/min for routine work (we pack our own from POROS
R10 or Columbus C18--its easy and students don't feel so bad when they muck
them up, which they do frequently). This will give you sensitivity in the
15-30 picomole range, with 4-8 fold increased sensitivity with a little
work to step down to 150 or 350 micron columns and stream splitting. You
don't need a lot of instrumental bells and whistles for lc/ms, but make
sure you can easily divert the salt laden break-through so it doesn't enter
the mass spectrometer. A small pump is easier to work with.
LC/MS is actually pretty easy, it doesn't even require a pump--I
often do it by setting up a step gradient in the loading loop (use a 1 mL
wide diameter Peek injection loop; rinse the loop with 80% AN, then inject
20-40 microliters of 5, 10, 15, 20, 25, 30, 40 and 50% AN. The steps mix
sufficiently and I can't tell the difference from the machine generated
gradient).
I don't bother with a UV detector.
Katheryn Resing