Analysis of menthol in three traditional Chinese medicinal herbs and their compound formulation by GC-MS

A GC-MS method was developed for identification and determination of menthol in three traditional Chinese medicinal herbs and their compound formulation, a granule for treating colds. Volatile oil was simultaneously distilled and extracted into ethyl ether in a unique glass extractor. The separation was performed on an HP-5 MS column. The standard addition method was used for quantitative determination of menthol content in herbal materials and in the granule. A component in the samples was chosen as the internal standard. The contents were calculated with the ratio of peak area percentage. Menthol was identified as the main component in Mentha haplocalyx Briq., and also existed in spikes of Schizonepeta tenuifolia Briq., Folium perilla frutescens (L.) Britt. and granules. The quantitative calibration range was 0.21-10.5 mg/mL. Good precision was demonstrated by an RSD < 4.0%. The mean content of menthol in Mentha haplocalyx Briq., spikes of Schizonepeta tenuifolia Briq., Folium perilla frutescens (L.) Britt. and granules was 121, 0.234, 1.03 and 1.84 mg/kg respectively.