4. The amount of camphor in an analgesic ointment is determined by GC using the

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4. The amount of camphor in an analgesic ointment is determined by GC using the method of internal standards. A standard sample is 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-L sample of the standard is injected, the FID signals for the two components are measured (in arbitrary units) as 67.3 for camphor and 19.8 for terpene hydrate.

A 53.6-mg sample of an analgesic ointment is 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 is cooled to below room temperature and filtered. The residue is washed with two 5-mL portions of CCl4 and the combined filtrates are collected in a 25-mL volumetric flask. After adding 2.00 mL of the internal standard solution, the contents of the flask are diluted to volume with CCl4. Analysis of an approximately 2-L sample gives FID signals of 13.5 for the terpene hydrate and 24.9 for the camphor. Report the %w/w camphor in the analgesic ointment 4. The amount of camphor in an analgesic ointment is determined by GC using the method of intemal standards. A standard sample is prepared by placing 45.2 mg of camphor and 2.00 mL of a 6.00 mg/mL intemal standard solution of terpene hydrate in a 25-mL volumetric flask and diluting to volume with CCL. When an approximately 2-uL sample of the standard is injected, the FIDsignals for the two components are measured (in arbitrary units) as 67.3 for camphor and 19.8 for terpene hydrate. A 53.6-mg sample of an analgesic ointment is prepared for analysis by placing it in a 50-mL Erlenmcycr flask along with 10 ml. of CCL. After heating to 50°C in a water bath, the sample is coolcd to below room temperature and filtered. The residue is washed with two 5-mL portions ofCCla and the combined filtrates are collected in a 25-mL volumetric flask. After adding 2.00 mL of the internal standard solution, the contents of the flask are diluted to volume with CCl. Analysis of an approximately 2-HL sample gives 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

Standard solution

Camphor = 45.2 mg/152.23 g/mol x 1000 x 0.025 L

                = 0.012 M

Terprene hydrate = 6 mg/ml x 2ml/25 ml

                             = 0.48 mg/ml

                             = 0.48 mg/190.283 g/mol

                             = 0.0025 M

using FID signals for the two components,

Response factor (RF) = (FID signal/concentration)camphor/(FID signal/concentration)terpene hydrate

                                   = (67.3/0.012)/(19.8/0.0025)

                                   = 0.708

Analysis of ointment sample

using response factor

0.708 = (24.9/concentration)camphor/(13.5/0.0025)

concentration of camphor = 0.0065 M

mass of camphor in ointment = 0.0065 M x 25 ml x 152.23 g/mol                                        

                                               = 0.025 mg

%w/w ca,phor in the analgesic oitment = 0.025 mg x 100/53.6 mg

                                                              = 0.047%

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