| Summary: | 碩士 === 高雄醫學大學 === 藥學研究所碩士班 === 92 === Analytical derivatization coupled with high-pressure liquid chromatography (HPLC) was used for the analysis of (+)-menthol and (-)-menthol. The method was based on the derivatization of (+)-menthol and (-)-menthol with a fluorescent derivatizing reagent, (+)-2-(6- methoxyl-2-naphthyl) propionyl chloride (MNP-COCl) in toluene. The resulting derivatives were separated on a C-8 column, using a mixed solvent of methanol : water : tetrahydrofuran (80:18:2, v/v) as the mobile phase. The separated (+)-menthol and (-)-menthol derivatives were monitored with a fluorimetric detector (excitation 235 nm and emission 350nm). α-Naphthyl caprate was used as an internal standard (I.S.), and the peak area ratios of (+)-menthol and (-)-menthol derivatives to I.S. were used for quantitative analysis.
The linear range of the method for the determination of (+)-menthol and (-)-menthol was 5~50μM. The detection limit (signal to noise ratio = 3, injected volume 10μL) of (+)-menthol and (-)-menthol was about 1μM. Several parameters affecting the derivatization of (+)-menthol and (-)-menthol were discussed including reaction solvent, amount of derivatizing reagent, base catalyst, reaction temperature and time.
Application of the method to the analysis of (-)-menthol in mint plants was studied. After toluene extraction of (-)-menthol from mint plants, the toluene extract was directly derivatized with MNP-COCl for HPLC-fluorescence detection.
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