Chromatographic purity
Adsorbent:
0.25-mm layer of chromatographic silica gel mixture.
Test solution
Dissolve an accurately weighed quantity of Proline in 0.1 N 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-Proline RS in 0.1 N hydrochloric acid to obtain a solution having a known concentration of about 0.05 mg per mL. Apply 5 µL. [NOTEThis solution has a concentration equivalent to about 0.5% of that of the Test solution.]
System suitability solution
Prepare a solution in 0.1 N hydrochloric acid containing 0.4 mg each of USP L-Proline RS and USP L-Threonine 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.