An ionic liquid piezoelectric gas sensor for the detection of polar and nonpolar organic vapors. The gas sensor can operate at high temperatures with a fast linear response which is also reversible. At high temperatures, the frequency change (.DELTA.f) versus concentration (C) curve mirrors the Henry's gas law, such that the concentration of a gas sample in liquid solvent is proportional to the concentration or partial pressure of the sample in gas phase. The gas sensor can be used for quantitative analysis of gas vapors and determination of Henry constants.