Packaging and storage—
Preserve in well-closed containers.
Specific rotation 
781S
:
between +22.4
and +24.7
.
Test solution:
20 mg per mL, in 6 N hydrochloric acid.
pH 791:
between 5.6 and 6.1 in a solution (1 in 100).
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%).
Chromatographic purity—
Adsorbent:
0.25-mm layer of chromatographic silica gel mixture.
Test solution—
Dissolve an accurately weighed quantity of Methionine in 0.3 M hydrochloric acid to obtain a solution having a concentration of 10 mg per mL. Apply 5 µL.
Standard solution—
Dissolve an accurately weighed quantity of USP L-Methionine RS in 0.3 M hydrochloric acid to obtain a solution having a known concentration of about 0.05 mg per mL. Apply 5 µL. [NOTE—This solution has a concentration equivalent to about 0.5% of that of the Test solution.]
System suitability solution—
Prepare a solution in 0.3 N hydrochloric acid containing 0.4 mg each of
USP L-Methionine RS and USP
L-Serine RS per mL. Apply 5 µL.
Spray reagent—
Dissolve 0.2 g of ninhydrin in 100 mL of a mixture of butyl alcohol and 2 N acetic acid (95:5).
Developing solvent system—
Prepare a mixture of butyl alcohol, glacial acetic acid, and water (60:20:20).
Procedure—
Proceed as directed for
Thin-Layer Chromatography under
Chromatography 621. After air-drying the plate, spray with
Spray reagent, and heat between 100
and 105
for about 15 minutes. Examine the plate under white light. The chromatogram obtained from the
System suitability solution exhibits two clearly separated spots. Any secondary spot in the chromatogram obtained from the
Test solution is not larger or more intense than the principal spot in the chromatogram obtained from the
Standard solution: not more than 0.5% of any individual impurity is found; and not more than 2.0% of total impurities is found.
Organic volatile impurities, Method I 467:
meets the requirements.
Assay—
Transfer about 140 mg of Methionine, 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 14.92 mg of C5H11NO2S.
;)
