Simple preparative gas chromatographic method for isolation of menthol and menthone from peppermint oil, with quantitative GC-MS and (1) H NMR assay.
The quantitative performance of a simple home-built preparative gas chromatography (prep-GC) arrangement was tested, incorporating a micro-fluidic Deans switch, with collection of the target compound in a deactivated uncoated capillary tube. Repeat injections of a standard solution and peppermint sample were made into the prep-GC instrument. Individual compounds were eluted from the trapping capillary, and made up to constant volume. Chloronaphthalene internal standard was added in some cases. Recovered samples were quantitatively assayed by using GC-MS. Calibration linearity of GC-MS for menthol standard area response against number of injections (2-20 repeat injections) was excellent, giving R(2)  of 0.996. For peppermint, menthol correlation over 2-20 repeated injections was 0.998 for menthol area ratio (versus IS) data. Menthone calibration for peppermint gave an R(2)  of 0.972. (1) H NMR spectroscopy was conducted on both menthol and menthone. Good correspondence with reference spectra was obtained. About 80 μg of isolated menthol and menthone solute was collected over a sequence of 80 repeat injections from the peppermint sample, as assayed by 600 MHz (1) H NMR analysis (∼100% recovery for menthol from peppermint). A procedure is proposed for prediction of number of injections required to acquire sufficient material for NMR detection.
College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea.
Hae Eun
HE
Park
Seung-Ok
SO
Yang
Sun-Hee
SH
Hyun
Shin Jung
SJ
Park
Hyung-Kyoon
HK
Choi
Philip J
PJ
Marriott
D002849:Chromatography, Gas; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D036142:Mentha piperita; D008610:Menthol / Q000302:isolation & purification*; D010938:Plant Oils / Q000737:chemistry*; D011522:Protons
D010938:Plant Oils; D011522:Protons; D008610:Menthol; C019466:menthone; C015424:peppermint oil