L-Menthol CAS 2216-51-5 Purity >99.5% (GC) Factory

Menthol [1490-04-6]
Menthol is an alcohol obtained from diverse mint oils or prepared synthetically. Menthol may be levorotatory (L-Menthol), from natural or synthetic sources, or racemic (DL-Menthol).
Packaging and storage-Preserve in tight containers, preferably at controlled room temperature.
Labeling-Label it to indicate whether it is levorotatory or racemic.
Identification-When it is triturated with about an equal weight of camphor, of chloral hydrate, or of phenol, the mixture liquefies.
Melting range of L-Menthol <741>: between 41° and 44°
Congealing range of DL-Menthol <651>-[NOTE-Perform this test preferably in a room having a temperature below 30° and a relative humidity below 50%.] Place about 10 g of racemic Menthol, previously dried in a desiccator over silica gel for 24 hours, in a dry test tube of from 18- to 20-mm internal diameter, and melt the contents at a temperature of about 40°. Suspend the test tube in water having a temperature of 23° to 25°, and stir the contents of the tube continually with a thermometer, keeping the bulb of the thermometer immersed in the liquid. Racemic Menthol congeals at a temperature between 27° and 28°. Shortly after the temperature has stabilized at the congealing point, add a few mg of dried racemic Menthol to the congealed mass, and continue the stirring: after a few minutes the temperature of the mass quickly rises to 30.5° to 32.0°.
Specific rotation <781S>: between -45° and -51° for L-Menthol; between -2° and +2° for DL-Menthol. Test solution: 100 mg per mL, in alcohol.
Limit of nonvolatile residue-Volatilize 2 g, accurately weighed, in a tared open porcelain dish on a steam bath, and dry the residue at 105° for 1 hour: the residue weighs not more than 1 mg (0.05%).
Chromatographic purity-
System suitability preparation-Dissolve decanol and Mentho in ether to obtain a solution having concentrations of about 0.05 mg of each per mL.
Test preparation-Dissolve 10 mg of Menthol in 50 mL of ether, and mix. Dilute 25 mL of this solution with ether to 100mL, and mix.
Chromatographic system-The gas chromatograph is equipped with a flame-ionization detector and contains a 1.8-m× 2-mm column packed with 10% phase G16 on support S1AB. The column is maintained at about 170°, the injection port is maintained at about 260°, and the detector block is maintained at about 240°. Dry helium is used as the carrier gas at a flow rate of about 50 mL per minute. Chromatograph the System suitability preparation, and record the peak responses as directed under Procedure: the retention time of menthol is about 0.7 relative to decanol. In a suitable chromatogram, the resolution R, of the 2 peaks is not less than 2.5, and the relative standard deviation of the ratio of the peak response obtained with Menthol to that obtained with decanol is not more than 2%.
Procedure-Inject about 2 µL of the Test preparation into the gas chromatograph, and measure the peak responses. The peak response due to menthol is not less than 97% of the sum of all the peak responses, excluding any due to the ether.
Readily oxidizable substances in DL-Menthol-Place 500mg of DL-Menthol in a clean, dry test tube, add 10 mL of a solution of potassium permanganate, prepared by diluting 3 mL of 0.1 N potassium permanganate with water to 100 mL, and place the test tube in a beaker of water at a temperature between 45° and 50°. Remove the tube from the bath at intervals of 30 seconds, and mix quickly by shaking: the purple color of potassium permanganate is still apparent after 5 minutes.