CONTINUOUS MEASUREMENT OF WATER IN ORGANIC SOLUTION BY MEMBRANE-INLET MASS-SPECTROMETRY

With a membrane made of a relatively polar material, membrane-inlet mass spectrometry can be used to measure the water activity in organic liquids of low dielectric constant. The detection limit for water depends on the solubility of water in the organic liquid. In butanol, hexanol, octanol and octane the detection limits at 45-degrees-C are 7, 4, 3 and 0.3 ppm, respectively. The half-time of the water response at 45-degrees-C is 20 s. The method can be used for continuous monitoring of water in reaction systems in organic solvents. Examples given are the condensation of 2,4-dimethyl-3-pentanone with phenylhydrazine in hexanol solution and the hydrolysis of acetylchloride in octane solution.