Analytical interference effects on laser-induced fluorescence of ethylene by selected molecular species

The interference of numerous compounds on the laser-induced fluorescence of ethylene at 10.6-mm was studied. The compounds studied were methane, propane, hexane, heptane, propylene, 1-butene, acetylene, benzene, cyclohexane, acetone, chloroform, carbon tetrachloride, methanol, ethanol, sulfur dioxide, nitrogen dioxide, nitric oxide, carbon dioxide, water, argon, helium, nitrogen, and air. Only some of these, in low concentrations, interfered at atmospheric pressure, but most interfered in evacuated systems. Compounds which absorbed the excitation 10.6μm radiation enhanced the fluorescence signals of ethylene, while non-absorbing compounds generally did not interfere. The quenching efficiencies of helium, argon, nitrogen, and methane on excited ethylene molecules were determined, and compared to values calculated from published data; good agreement was found except for methane. Quenching experiments with higher concentrations of added compounds were also performed.