Determination of l-menthol in pharmaceutical products by high performance liquid chromatography with polarized photometric detection.

A simple analytical method for l-menthol by high-performance liquid chromatography with a polarized photometric detector was established. The polarized photometric detector was constructed with two polarizers mounted on both sides of the flow cell in a conventional photometric detector and can be easily used for the detection of optically active compound, such as l-menthol. This study was conducted with a newly developed split-cell assembly in order to increase the sensitivity. The characteristic of this method is the ability to determine optically active compounds selectively among the other coexisting materials and the pretreatment of the sample can be very simple or not required at all. The detection of l-menthol by this method is 0.5 microgram. A good agreement was shown between another commonly used GC method and the method described in this paper.