C40H71NO14·C12H26O4S 1056.39

Erythromycin,2¢-propanoate,dodecyl sulfate (salt).
Erythromycin 2¢-propionate dodecyl sulfate (salt) [3521-62-8].

Packaging and storage— Preserve in tight containers.

USP Reference standards á11ñ— USP Erythromycin RS.USP Erythromycin Estolate RS.

Identification,Infrared Absorption á197Kñ.

Crystallinity á695ñ: meets the requirements.

Water,Method Iá921ñ: not more than 4.0%,20mLof methanol containing 10%of imidazole being used in place of methanol in the titration vessel.

Free erythromycin— Prepare a test solution of it in methanol containing 10.0mg per mL.Prepare a Standard solution of USP Erythromycin RSin methanol containing 0.3mg per mL.[NOTE—Prepare these solutions immediately before use.]Prepare a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Before using,place the plate in an unlined developing chamber containing about 100mLof methanol,and allow the solvent front to move to the top of the plate,marking the direction of travel.Remove the plate,and allow to dry.Apply separate 1-µLvolumes of the test solution and the Standard solution on the plate,allow the spots to dry,and develop the chromatograms in a freshly prepared solvent system consisting of a mixture of methanol and chloroform (85:15)until the solvent front has moved about one-half of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the plate to dry.Place the plate under a hood,and spray uniformly with a solution consisting of 150mg of xanthydrol dissolved in a mixture of hydrochloric acid and glacial acetic acid (92.5:7.5).Heat the sprayed plate in an oven at 100for 5minutes.[Caution—Avoid exposure to acid fumes when removing the plate from the oven. ]Examine the plate for reddish violet spots:free erythromycin has an RFvalue of about 0.3,and erythromycin estolate has an RFvalue of about 0.7.Any spot corresponding to free erythromycin obtained from the test solution does not exceed in size or intensity that of the principal spot obtained from the Standard solution (3.0%).

Assay— Proceed with Erythromycin Estolate as directed for erythromycin under Antibiotics—Microbial Assays á81ñ,using an accurately weighed quantity of Erythromycin Estolate dissolved in methanol to obtain a solution containing the equivalent of 1.0mg of erythromycin per mL.Immediately dilute quantitatively with 9volumes of Buffer No.3,and allow to stand at room temperature for 18hours.Dilute a portion of this solution quantitatively with Buffer No.3to obtain a Test Dilutionhaving a concentration assumed to be equal to the median dose level of the Standard.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 763

Phone Number:1-301-816-8335