Search USP29  
Click to View Image
C11H12N2O2 204.23

L-Tryptophan [73-22-3].
» Tryptophan contains not less than 98.5 percent and not more than 101.5 percent of C11H12N2O2, as L-tryptophan, calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
Specific rotation 781S: between 29.4 and 32.8.
Test solution: 10 mg per mL, in water (heat gently to dissolve, if necessary).
pH 791: between 5.5 and 7.0, in a solution (1 in 100).
Loss on drying 731 Dry it at 105 for 3 hours: it loses not more than 0.3% of its weight.
Residue on ignition 281: not more than 0.1%.
Chloride 221 A 0.73-g portion shows no more chloride than corresponds to 0.50 mL of 0.020 N hydrochloric acid (0.05%).
Sulfate 221 A 0.33-g portion shows no more sulfate than corresponds to 0.10 mL of 0.020 N sulfuric acid (0.03%).
Iron 241: 0.003%.
Heavy metals, Method II 231: 0.0015%.
Organic volatile impurities, Method IV 467: meets the requirements.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Transfer about 200 mg of Tryptophan, accurately weighed, to a 125-mL flask, dissolve in a mixture of 3 mL of formic acid and 50 mL of glacial acetic acid, 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 20.42 mg of C11H12N2O2.
Auxiliary Information— Staff Liaison : Lawrence Evans, III, Ph.D., Scientist
Expert Committee : (DSN05) Dietary Supplements - Non-Botanicals
USP29–NF24 Page 2224
Pharmacopeial Forum : Volume No. 31(5) Page 1410
Phone Number : 1-301-816-8389