The vapour pressures of several ionic liquids, liquid polymers and derivatives of glycerol were investigated by thermogravimetric analysis (TGA). The experimental method is described and discussed. Vapour pressure data for various solvents with low vapour pressures are reported at 100-120 degrees C. The thermogravimetric method for vapour pressure measurement is useful for the rapid screening of solvents. Ionic liquids have a low but detectable vapour pressure at 100-120 degrees C. The vapour pressures of liquid polymers such as poly(ethylenimine) and polyethylene glycols are in the same range, which might make these substances a less expensive alternative to ionic liquids.