An apparatus for the preparation of mixtures of fluoro-organic compounds and air, and a method for the determination of fluorine in such compounds are described. The analysis involves 1 removing the fluoro-organic compounds by scrubbing the air mixture with l-hexanol, 2 decomposing the fluoro-organic compound by refluxing with sodium, 3 extracting with water the sodium fluoride thus formed and 4 titrating the fluoride ion with thorium nitrate solution, using Solochrome Brilliant Blue BS as indicator. This method has been tested in the concentration range of 0.002 to 2 mg. of fluoride which is equivalent to 0.01 to 8 mg. of fluoro-organic compound per liter of air. Three fluoro-organic compounds were analyzed. With methyl fluoroacetate in the range 0.01 to 8 mg. per liter, a recovery of about 90 was obtained. About 90 of 2-fluoroethanol was recovered from air mixtures when the concentration was 0.02 to 3 mg. per liter when the concentration was 0.01 to 0.03 mg. per liter, the recovery was only about 75. The recovery of di-isopropylfluorophosphate is 72 at a concentration of 0.02-0.04 mg. per liter, 84 at 0.07-0.15 mg. per liter, and 68 at 1-2 mg. per liter. By using two scrubbers in series, 90 of di-isopropyl fluorophosphate was recovered at a concentration of 1 to 2 mg. per liter.