Method for determining content of menthol in preparation of traditional chinese medicine composition

A method for determining the content of menthol in a preparation of a traditional Chinese medicine composition, the preparation of a traditional Chinese medicine composition is prepared from the following raw materials with the following parts by weight:

• Fructus Forsythia 200-300, Herba Ephedrae 60-100, rheum 40-60, Herba Houttuyniae 200-300, Flos Lonicerae 200-300, Radix Isatidis 200-300, Herba Pogostemonis 60-100, Rhizoma Dryopteris Crassirhizomae 200-300, Rhodiola rosea L. 60-100, menthol 5-9, Semen Armeniacae Amarum 60-100, Radix Glycyrrhizae 60-100 and gypsum 200-300, wherein the content of the menthol is determined according to the method as follows:
• 1) extracting the preparation of the traditional Chinese medicine composition using a non-polar solvent to obtain a test solution;
• 2) preparing a solution of menthol reference substance with a menthol concentration of 4.80 μg/mL or more, preferably 17.65 μg/mL or more, more preferably 0.2-0.3 mg/mL by a menthol reference substance using the same non-polar solvent as that in step 1);
• 3) taking the solution of menthol reference substance and the test solution in an equal amount respectively, injecting the solutions into a gas chromatograph, and determining the contents of menthol, wherein the conditions for chromatography are:
• the column is a weak polar capillary chromatographic column;
• the column temperature is increased according to the following temperature programming:
• initial temperature is 80-100° C., and is kept for 10-15 minutes, increased to 120-160° C. at a rate of 6-10° C. per minute, kept for 1.5-3.5 minutes, then increased to 240-300° C. at a rate of 100-160° C. per minute, kept for 5-20 minutes.