MRG LabNotes 1998
Using the Perkin-Elmer DSC7
Precautions: think about these things before you run the
- Make sure the purge nitrogen is on at the right rate
- Never run halogenated materials: they eat the cell!
- Never degrade samples in the cell: but you have to know the degradation
temperature first; how? By running a TGA or capillary mp first!
- Make sure sample is dry or leave the lid off to let volatiles leave.
- Use clean sample pans so nothing contacts the cell surface; be sure
not to let the sample you are analyzing melt and flow onto the cell!
- Never heat above 500C with aluminum pans: they'll melt!
- Make sure calibration has been done at your heating rate.
- Cooling to subambient requires very special precautions: don't do
Preparing a sample: do this before you set up the instrument; in
fact make up all your samples so they are ready to run before you
waste machine time (and that of your classmates) by trying to
weigh and run the DSC at the same time.
- Your sample should be powdered, a pressed film, a "snippet"
of solid, a fiber, whatever, as long as it's clean and dry and you
know it's decomp temp!
- Weigh pan, put your sample in, weigh again: you want about15-20
- Crimp a top on if needed (you must have someone show you
this: you break it, you buy it!)
Turning on the instrument: you must do all of these
things and in the order given (or face banishment to Easter
- Sign the log book before you start; that way, if you break
it, we got ya'!
- Turn on the nitrogen purge (notice we said this twice? Could there
be a reason? Why is this important?)
- Turn on the "Analyzer" and wait 10 sec.
- Turn on the "TAC" (and you better know before which it is!)
and wait for all lights to go out except the ready light (and that stays
- Turn on the "computer" (we just put it in quotes for fun-
you know what it is- a tool of the devil!)
- Select Multitasking from the two choices: think hard!
- Run a baseline if you need to; if you're running a bunch together or
with the class, you may already have a recent baseline, so check with
the "Powers That Be" (the TA). By the way, be sure the
baseline you have covers the same or larger temperature range as that of
the sample range you want to look at... or it won't work.
- Do the following in order (think hard again):
- Hit "F1- Experimental Parameters"
- Hit "F2- Conditions at End of Run" (choose H for hold, S for
temp, L for load temp and cooling rate if you want a controlled cool but
mostly you don't)
- F3 is Label Experiment (name it something you'll remember and then
write it down cause you won't)
- F4- Direct Temperature Control (use this to get directly to the start
- F7- View Parameters (just to check)
- Prepare and put sample pan on right cell with empty pan on the
- F6- Start Run (and remember the name of the baseline file, usually
- F8- Save Data (the very first thing you do after the run so
you don't loose it!)
- F9- puts you in analysis mode (or mood, depending on who you're with)
and you might need some instructions later on how to use this mood
- F10- Exit (obvious but if you didn't save your data, "Hasta la
Shutting down the DSC-7 (but only do this if no one else
will use it soon)
- F10- Exit (used in both Set-up and Analysis Modes)
- F2 actually exits you from either program
- Go to DOS (maybe; there is another option- later)
- Follow steps 4 through 1 backwards (in "Turning on...")
Doing an experiment: let's do PET first just for fun;
options may vary for your system...
- Snip out a little piece of some drink bottle (preferably plastic);
a hole punch works
- Make a DSC sample by crimping the sample (as above)
- Turn on the DSC, put in your sample (right or left side??),
set your parameters, acquire data, work it up, plot it, save it, shut
off machine, have a beer (oops! can't do that on campus!), done.
- Whoa! Not so fast! While you had the machine on, why didn't you run
the same sample again? or a couple more times? In fact, you normally run
the same sample (same pan and everything: don't even take it out of the instrument) three
times. The first run gets rid of thermal history (and any residual
solvent or volatiles present), the second should be good but you
check it by running it a third time (three's a charm, right?)