Abstract: A multiphase microreactor includes gas and liquid microchannels separated by a nanoporous membrane. Rapid mass transfer of gas samples into the liquid electrolyte allows the microchannel/membrane assembly to be used as a fast and sensitive gas sensor. When the oxime chemistry is adapted into the microchannel sensor, the microchannel sensor selectively responds to organophosphates and organophosphate simulants. In addition, a double microchannel design may be used to reduce voltage drift and incorporate a reference electrode into the sensor assembly. Methods of detecting organophosphates are also disclosed.