A: Infrared Absorption 197K.

B: In the test for Chromatographic purity, the principal spot in the chromatogram obtained from Test solution 2 observed after spraying with the ninhydrin solutions corresponds in RF value, color, and size to that in the chromatogram obtained from Standard solution 1.

C: To 10 mL of a 1 in 20 solution of it add 5 mL of hydrochloric acid, and extract with three 10-mL portions of ether. Evaporate the combined ether extracts to dryness, wash the residue with water, and dry at 105: the residue of adipic acid so obtained melts at between 150 and 154.

Solvent— Prepare a mixture of 13.5 N ammonium hydroxide and dehydrated alcohol (3:2).

Test solution 1— Prepare a solution of Piperazine Adipate in Solvent containing 100 mg per mL.

Test solution 2— Mix 1 mL of Test solution 1 and 9 mL of Solvent.

Standard solution 1— Prepare a solution of USP Piperazine Adipate RS in Solvent containing 10 mg per mL.

Standard solution 2— Prepare a solution of ethylenediamine in Solvent containing 0.25 mg per mL.

Standard solution 3— Prepare a solution of triethylenediamine in Solvent containing 0.25 mg per mL.

Resolution solution— Prepare a solution in Solvent containing 0.25 mg of triethylenediamine and 10 mg of Piperazine Adipate per mL.

Procedure— Separately apply 5-µL portions of Test solution 1, Test solution 2, Standard solution 1, Standard solution 2, Standard solution 3, and the Resolution solution to a suitable thin-layer chromatographic plate (see Chromatography 621), coated with a 0.25-mm layer of chromatographic silica gel. Allow the spots to dry, and develop the chromatograms in a solvent system consisting of a freshly prepared mixture of acetone and 13.5 N ammonium hydroxide (80:20) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and dry the plate at 105. Spray the plate with a 0.3% solution of ninhydrin in a mixture of butyl alcohol and glacial acetic acid (100:3). Spray the plate again with a 0.15% solution of ninhydrin in dehydrated alcohol, dry the plate at 105 for 10 minutes, and examine the plate: any secondary spot in the chromatogram obtained from Test solution 1 is not more intense than the principal spot in the chromatogram obtained from Standard solution 2 (0.25%). Spray the plate with 0.1 N iodine TS, allow to stand for 10 minutes, and examine the plate: any spot corresponding to triethylenediamine in the chromatogram obtained from Test solution 1 is not more intense than the principal spot in the chromatogram obtained from Standard solution 3 (0.25%). In a valid test, the chromatogram obtained from the Resolution solution shows a spot due to triethylenediamine clearly separated from the principal spot. Disregard any spot at the origin of any chromatogram.