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 45.21 mg of camphor and 2.000 mL of a 6.000 mg/L internal standard solution of terpene hydrate in a 25-mL volumetric flask and diluting it to volume with CCl4. When an approximately 2 microliter sample of the standard was injected, the FID signals for the two components were measured as 67.14 for camphor and 19.13 for terpene hydrate. A 53.61 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 2.000 mL of the internal standard solution, the contents of the flask were diluted to volume with CCl4. Analysis of an approximately 2 microliter sample gave FID signals of 13.43 for the terpene hydrate and 24.31 for the camphor. Report the %w/w camphor in the analgesic ointment.

Answer 1

If GC experiments were performed in idential condition then the retention time in GC will be similar. The retantion time of a perticular molecule will be same if the experiment is performed in identical condition as if temperature ramp or flow of gas etc. I belive that the parameters while performing GC experiments were changed. And hence

FID signals for the camphor and terpene hydrate observed in two different places as 67.14 and 24.31for camphor, and 13.43 and 19.13 for terpene hydrate respectively.