怎么购买最好的质谱仪

Dear All,

.......................................... "what instrument should I
buy for a given purpose". There is no general answer to that, as only
*you* can know what is best for your purpose.

There was a nice report on an ASMS workshop on this topic a few years
back, but I don^t have the precise reference at hand right now ...
however, speaking from my own experience:

(1) Define what the instrument MUST be able to to. That may be
something technical ("exceed resolution X at mass y"), or a
specification like "quantify x pg of compound A per kg of y".

(2) Define what the instrument SHOULD be able to do ("nice to have").

(3) Define your budget.

(4) Contact the manufacturers and explain them (1)-(3). Take care
that especially (1) is defined very clearly ("Using your MS without
options, can we indentify and quantify x pg of compound A per kg of y
using the following setup... , yes or no?)"

- Set a reasonable deadline for the answers.

(5) Collect the answers and compare:

- If any of the answers needed under (1) is negative, that
  instrument ist "out". All under (1) are "go/no go" criteria!

- anything that exceeds (3) by far is "out" for obvious reasons.
  However, if the difference is only weak, they may still want
  to discuss ;-)

- If an answer is not clear (e.g. you requested a detection
  limit for drug X but they gave you data for Reserpine), ask
  for clarification. If you don^t get a clear answer ...

- Already at this stage, watch carefully for the smallprint in the
  offers. I often stumble upon things like a 15" CRT monitor, while
  the machine in the prospectus is equipped with a 19" TFT ... or
  "free software updates", while "software upgrades" are an
  expensive, different story. Or the fact that, to perform the
  database searches they promised, you need an extra 4-processor
  workstation with additional licenses, etc. You get the idea.

(6) If several candidates fulfill (1) and (3), clarify the selection
further with the help of (2).

(7) If several candidates fulfill (1) and (2) and (3), proceed to
practical experiences:

- Contact the vendor and request a date in the demo lab where
  they can measure your "real" samples, either in your presence
  or without you.

- Try to keep these dates (for all vendors) as close as possible.

- Be open: Communicate beforehand what and how you want to analyse
  and which setup you need (HPLC, solvents etc.). Make sure your
  analytical method is sufficiently rugged so that you can easily
  transfer it from HPLC brand A on MS X to brand B on MS Y.

- Do not take your most challenging samples, but samples where
  you know what you *can* obtain. It^s of no use to do structure
  elucidation of an unknown in a demo trial.

- Depending on your needs, take enough samples to do overnight runs
  (you asked for "sensitive and stable ... in serum/blood/urine").

- In a demo lab, you never test the instrument alone but also the
  demo chemist. He/she is only a human being, just like you.

- Don^t take precious, unique samples. It may all go wrong.

- Keep enough sample for the other manufacturer(s) you are going
  to test.

(8) Run the same test with all (!) manufacturers, then compare your
experiences (obtained results, instrument  usability, ease of
processing, and whatever else counts for you ... except for the hotel
;-). The decision should not be difficult now.

(9) Once you have  made up your mind and are going to "make the
deal", watch carefully for the smallprint in the contract (already
mentioned above). Include your specs from (1) in the contract!

"I said I wanted it to be complete. And no sales tricks, please".

(10) Once the contract is signed, write to the other manufacturers
with whom you spent some time and explain them why you bought the
"other" instrument, and not theirs. It helps them to improve and to
serve you better the next time.