Simultaneous determination of ethanol and methanol in non-alcoholic beverages by precolumn derivatization and liquid chromatography with fluorescence detection

The determination of ethanol content in non-alcoholic beverages is driven by health concerns and is often imposed by regulating agencies. On the other hand, methanol poisoning leads to high health risks. In addition, the application of the Halal concept in Islamic countries requires the availability of efficient analytical methods. This work reports the development of a simple and sensitive HPLC method for the simultaneous determination of ethanol and methanol in juices and beverages. The method is based on the formation of a stable derivative via the reaction of ethanol and methanol with 9-fluorenylmethyl chloroformate (Fmoc-Cl). The resulting derivatives are detected by a fluorescence detector. The method’s LODs and LOQs were 0.004 g/L and 0.01 g/L, for methanol, and 0.015 g/L and 0.05 g/L, for ethanol, respectively. The mean recovery ranged from 98–109% for both methanol (RSD = 3.7%), and ethanol (RSD = 4.1%). This approach of determination is sensitive and simple in that it requires only a 100 µL sample volume and the reaction product (derivative) can be directly injected without further extraction or pre-concentration. Analysis of a number of non-alcoholic drinks from the domestic market showed that the ethanol content ranged between 0.11 - 0.71 g/L.