Procedure
USP grade acetaminophen (98.0−101.0%) and α-lactose monohydrate
(≥99% total lactose) were used as received from SigmaAldrich.
Thermograms were generated using a PerkinElmer DSC
6000 equipped with an Intracooler SP and a PerkinElmer TGA
4000 equipped with a Polyscience chiller unit, and nitrogen
purge gas at 20 mL/min. Pyris Software was utilized for data
analysis. Sample sizes ranged from 2 to 5 mg and 5 to 15 mg for
DSC and TGA, respectively. Hermetically sealed aluminum pans,
with or without a pinhole, were used for DSC, while ceramic
crucibles were used for TGA samples. Thermal microscopy was
performed using an Olympus BX60 polarizing light microscope
equipped with a Linkam LS350 Hot Stage/Linksys Software and
Paxcam 2+ digital camera/Pax-It! Software and a 20× objective.
A small amount of compound was placed on a microscope
slide and covered with type A immersion oil (Cargille). Students
collected photomicrographs at temperatures corresponding to
any changes in the sample visually observed as a function of
temperature. Heating programs for all thermal methods
consisted of a heating rate of 10 °C/min from 30 to 220 °C
for acetaminophen and 30 to 250 °C for α-lactose.