The amount of camphor in an analgesic ointment can be determined by GC using the

Question

The amount of camphor in an analgesic ointment can be determined by GC using the method of internal standards. 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 25.00 mL volumetric flask and diluting to volume with CCl_4. When an approximately 2 mu L 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 the analgesic ointment was prepared for analysis by placing it into a 50.0 mL volumetric flask along with 10 mL of CCl_4. After heating to 50 degree 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 CCl_4, and the combined filtrates were collected in a 25.00 mL volumetric flask. After adding 2.00 mL of the internal standard solution, the contents of the flask were diluted to volume with CCl_4. Analysis of an approximately 2 mu L 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.

Explanation / Answer

7. analysis of camphor

Standard sample with,

45.2 mg/25 = 1.808 mg/ml Camphor

6 x 2/25 = 0.48 mg/ml of terpene hydrate as internal standand

2 uL aliquot gave GC signal = 67.3 of camphor and 19.8 for terpene hydrate

Response factor = (67.3/1.808)/(19.8/0.48) = 3.4

Sample of analgesic ointment analysis

concentration of camphor in diluted sample = 24.9 x 0.48/3.4 x 13.5 = 0.2604 mg/ml

In 25 ml = 0.2604 x 25 = 6.51 mg camphor is present

%w/w camphor in analgesic ointment = 6.51 x 100/53.6 = 12.14%

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.