Evaluation of a Polymer Film Impregnated With Reagent for the Detection and Determination of Chlorine in Air.

A new method for the direct detection and determination of chlorine in air has been devised. The method is based on the permeation of the gas through a silicone-polycarbonate copolymer film impregnated with a colorimetric reagent. The impregnation of the film with reagent was achieved by dissolving both a polymer film and a reagent in a common volatile solvent (CHCl(,3)), followed by casting on a leveled surface to allow the solvent to evaporate, thus forming a polymer film containing suspended reagent. The polymer films impregnated in such manner, were uniform and transparent. A spectrophotometer was used for monitoring the change in color, observed when the permeant gas reacted with the reagent inside the film. Films impregnated with o-tolidine, 3,3\u27,5,5\u27-tetramethylbenzidine and dithizone, were examined. The response of the film was studied, as a function of concentration and duration of exposure. The response was not directly proportional to dosage (Cxt), which limits the use of the film as a dosimeter for personal monitoring. The response of the film impregnated with excess reagent was directly proportional to concentration of exposure, for a constant duration of time exceeding twelve minutes. The film, therefore, is useful in a manner similar to test papers or detector tubes. Yet, the determination is quantitative as opposed to semi-quantitative determination achieved by the latter. A polymer film impregnated with 3,3\u27,5,5\u27-tetramethylbenzidine, showed accuracy within (+OR-)6% in the range (0.5ppm - 6.0ppm) of chlorine in air, for a constant duration of exposure equal to fifteen minutes. The maximum relative error was (+OR-)18% for 0.5ppm. The detection limit was as low as 0.1ppm, for an exposure duration of fifteen minutes, as the least perceivable change in color by the naked eye. Less accuracy ((+OR-) 13%) was attained with the film impregnated with o-tolidine or dithizone