Trace determination of methanol in water-ethanol solution by derivatization and high-performance liquid chromatography.

A simple and sensitive high-performance liquid chromatographic method has been established for the determination of methanol in water-ethanol solution. The method is based on the transfer of the methoxide anion, which is formed from methanol under strong alkaline treatment in aqueous solution, by benzalkonium chloride into the dichloromethane organic phase for derivatization with 3-bromomethyl-7-methoxy-1,4-benzoxazin-2-one. The derivative obtained was separated on a LiChrospher diol column with n-hexane-dichloromethane (9:1, v/v) as the mobile phase. Several parameters affecting the partition/derivatization of methanol were investigated. The linear range for the determination of methanol was 2-20 mumol/ml; the detection limit (signal-to-noise ratio = 5; sample size, 10 microliters) of methanol was about 0.10 mumol/ml (R.S.D. = 16%, n = 3). The method has been satisfactorily applied to the assay of methanol in spiked commercial liquors.