Tryptophan
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L-Tryptophan.
L-Tryptophan [73-22-3].
»Tryptophan contains not less than 98.5percent and not more than 101.5percent of C11H12N2O2,as L-tryptophan,calculated on the dried basis.
Packaging and storage—
Preserve in well-closed containers.
Identification,Infrared Absorption á197Kñ.
Specific rotation á781Sñ:
between -29.4
and -32.8.
and -32.8.
Test solution:
10mg per mL,in water (heat gently to dissolve,if necessary).
pHá791ñ:
between 5.5and 7.0,in a solution (1in 100).
Loss on drying á731ñ—
Dry it at 105for 3hours:it loses not more than 0.3%of its weight.
for 3hours:it loses not more than 0.3%of its weight.
Residue on ignition á281ñ:
not more than 0.1%.
Chloride á221ñ—
A0.73-g portion shows no more chloride than corresponds to 0.50mLof 0.020Nhydrochloric acid (0.05%).
Sulfate á221ñ—
A0.33-g portion shows no more sulfate than corresponds to 0.10mLof 0.020Nsulfuric acid (0.03%).
Iron á241ñ:
0.003%.
Heavy metals,Method IIá231ñ:
0.0015%.
Organic volatile impurities,Method IVá467ñ:
meets the requirements.
Assay—
Transfer about 200mg of Tryptophan,accurately weighed,to a 125-mLflask,dissolve in a mixture of 3mLof formic acid and 50mLof glacial acetic acid,and titrate with 0.1Nperchloric acid VS,determining the endpoint potentiometrically.Perform a blank determination,and make any necessary correction.Each mLof 0.1Nperchloric acid is equivalent to 20.42mg of C11H12N2O2.
Auxiliary Information—
Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(DSN)Dietary Supplements:Non-Botanicals
USP28–NF23Page 1999
Phone Number:1-301-816-8389