Diphenhydramine Citrate
C17H21NO·C6H8O7 447.48

Ethanamine, 2-(diphenylmethoxy)-N,N-dimethyl-, 2-hydroxy-1,2,3-propanetricarboxylate (1:1).
2-(Diphenylmethoxy)-N,N-dimethylethylamine citrate (1:1) [88637-37-0].
»Diphenhydramine Citrate contains not less than 98.0 percent and not more than 100.5 percent of C17H21NO·C6H8O7, calculated on the dried basis.
Packaging and storage— Preserve in tight, light-resistant containers.
Solution: 700 µg per mL.
Medium: water.
C: It responds to the test for Citrate 191.
Melting range 741: between 146 and 150, but the range between beginning and end of melting does not exceed 2.
Loss on drying 731 Dry it at 105 for 3 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281 To about 8 g, accurately weighed, add 5 mL of sulfuric acid, and char. After the substance is thoroughly charred, add 4 mL of nitric acid and a few drops of sulfuric acid, heat gently until fumes are no longer evolved, and ignite at 800 ± 25 until the carbon is consumed. Place in a muffle furnace at 550 ± 50 for about 1 hour. Continue the ignition until constant weight is attained: not more than 0.1% remains.
Assay— Dissolve about 1.6 g of Diphenhydramine Citrate, accurately weighed, in a mixture of 100 mL of glacial acetic acid and 20 mL of xylene. Add 20 mL of mercuric acetate TS, and titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 44.75 mg of C17H21NO·C6H8O7.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Daniel K. Bempong, Ph.D.
Senior Scientist
(MDPS05) Monograph Development-Pulmonary and Steroids
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2174
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.