The amount of camphor in an analgesic ointment can be
determined by GC using the method of internal standards.24
A standard sample was prepared by placing 45.2 mg of
camphor and 2.00 mL of a 6.00 mg/mL internal standard
solution of terpene hydrate in a 25-mL volumetric flask and
diluting to volume with CCl4. When an approximately 2-mL
sample of the standard was injected, the FID signals for the
two components were measured (in arbitrary units) as 67.3
for camphor and 19.8 for terpene hydrate. A 53.6-mg sample
of an analgesic ointment was prepared for analysis by placing
it in a 50-mL Erlenmeyer flask along with 10 mL of CCl4.
After heating to 50 °C in a water bath, the sample was cooled
to below room temperature and filtered. The residue was
washed with two 5-mL portions of CCl4, and the combined
filtrates were collected in a 25-mL volumetric flask. After
adding 2.00 mL of the internal standard solution, the contents
of the flask were diluted to volume with CCl4. Analysis of an
approximately 2-mL sample gave FID signals of 13.5 for the
terpene hydrate and 24.9 for the camphor. Report the %w/w
camphor in the analgesic ointment.