A novel composite film for detection and molecular weight determination of organic vapors

A novel vapor-sensitive composite film comprising cellulose acetate and a representative compound (1-n-butyl-2,3-dimethylimidazolium hexafluorophosphate) from a Group of Uniform Materials Based on Organic Salts (GUMBOS) has been developed and characterized. The vapor sensing characteristics of the film is investigated using a quartz crystal microbalance (QCM) transducer. The material exhibited greatly improved performance characteristics toward a number of organic vapors. It is demonstrated that the ratio of the change in resonance frequency (Δf) to the change in motional resistance (ΔR) is a concentration-independent quantity proportional to the molecular weight of the absorbed chemical species. To the best of our knowledge, this is the first study to show a direct relationship between Δf/ΔR and the molecular weight of analytes. This unique finding should prove extremely useful for easy identification and molecular weight determination of a broad range of chemical vapors.