Click to View Image
C20H28O2 300.44

Retinoic acid.
all trans-Retinoic acid [302-79-4].
» Tretinoin contains not less than 97.0 percent and not more than 103.0 percent of C20H28O2, calculated on the dried basis.
Packaging and storage— Preserve in tight containers, preferably under an atmosphere of an inert gas, protected from light.
USP Reference standards 11
USP Isotretinoin RS
USP Tretinoin RS
note—Avoid exposure to strong light, and use low-actinic glassware in the performance of the following procedures.
B: Ultraviolet Absorption 197U
Solution: 4 µg per mL.
Medium: acidified isopropyl alcohol (prepared by diluting 1 mL of 0.01 N hydrochloric acid with isopropyl alcohol to 1000 mL).
Absorptivities at 352 nm, calculated on the dried basis, do not differ by more than 3.0%.
Loss on drying 731 Dry it in vacuum at room temperature for 16 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Limit of isotretinoin—
Mobile phase— Prepare a suitable filtered and degassed mixture of isooctane, isopropyl alcohol, and glacial acetic acid (99.65:0.25:0.1), making adjustments if necessary (see System Suitability under Chromatography 621).
System suitability solution— Dissolve a quantity of USP Tretinoin RS in a minimum amount of methylene chloride, add a suitable amount of isooctane to obtain a solution having a tretinoin concentration of about 250 µg per mL, and mix.
Standard solution— Dissolve an accurately weighed quantity of USP Isotretinoin RS in a minimum quantity of methylene chloride, and add isooctane to obtain a solution having a known concentration of about 250 µg per mL.
System suitability preparation— Pipet 5 mL of Standard solution into a 100-mL volumetric flask, add System suitability solution to volume, and mix.
Standard preparation— Pipet 5 mL of Standard solution into a 100-mL volumetric flask, add isooctane to volume, and mix.
Test preparation— Transfer about 25 mg of Tretinoin, accurately weighed, to a 100-mL volumetric flask, dissolve in a minimum quantity of methylene chloride, add isooctane to volume, and mix.
Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 352-nm detector and a 4.0-mm × 25-cm column containing packing L3. The flow rate is about 1 mL per minute. Chromatograph about 20 µL of System suitability preparation, and record the peak responses. The relative retention times for isotretinoin and tretinoin are about 0.84 and 1.00, respectively. The relative standard deviation of the isotretinoin peak response in replicate injections is not more than 2.0%, and the resolution, R, of isotretinoin and tretinoin is not less than 2.0.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Test preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of isotretinoin taken by the formula:
10(C / W)(rU / rS)
in which C is the concentration, in µg per mL, of USP Isotretinoin RS in the Standard preparation, W is the weight, in mg, of Tretinoin taken, and rU and rS are the peak responses of the isotretinoin peaks obtained from the Test preparation and the Standard preparation, respectively. The content of isotretinoin is not more than 5.0%.
Assay— Dissolve about 240 mg of Tretinoin, accurately weighed, in 50 mL of dimethylformamide, add 3 drops of a 1 in 100 solution of thymol blue in dimethylformamide, and titrate with 0.1 N sodium methoxide VS to a greenish endpoint. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium methoxide is equivalent to 30.04 mg of C20H28O2.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Feiwen Mao, M.S.
(MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 3779
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.