Electrochemical Oxidation and Sensing of Methylamine Gas in Room Temperature Ionic Liquids

The electrochemical behavior of methylamine gas in several room temperature ionic liquids (RTILs), [C(2)mim][NTf2], [C(4)mim][NTf2], [C(6)mim][FAP], [C(4)mpyrr][NTf2], [C(4)mim][BF4], and [C(4)mim][PF6], has been investigated on a Pt microelectrode using cyclic voltammetry. A broad oxidation wave at approximately 3 V, two reduction peaks, and another oxidation peak were observed. A complicated mechanism is predicted based on the voltammetry obtained, with ammonia gas as a likely byproduct. The currents obtained suggest that methylamine has a high solubility in RTILs, which is important for gas-sensing applications. The analytical utility of methylamine was then studied in [C(4)mpyrr][NTf2] and [C(2)mim][NTf2]. A linear calibration graph with an R-2 value of 0.99 and limits of detection of 33 and 34 ppm were obtained, respectively, suggesting that RTILs are favorable nonvolatile solvents for the electrochemical detection of highly toxic methylamine gas.