An Optical Dosimeter for the Selective Detection of Gaseous Phosgene with Ultralow Detection Limit.

We present here a cheap, fast, and highly selective dosimeter for the colorimetric detection of gaseous phosgene with an ultralow detection limit. The disposable device is based on Harrison's reagent supported into a porous nanocrystalline TiO2 matrix film. We exposed the films to phosgene streams while the absorbance was monitored by an optic fiber in a gas chamber. The pronounced spectral changes were unaffected by humidity and oxygen and permitted us to use the response rate at 464 nm as a very stable calibration signal for quantitative analysis purposes. The use of a specific sensing reaction guaranteed a very high selectivity of the device even against saturated vapors of primary interferences like halide gases and other oxidizing and volatile agents. With this simple method, whose response is compatible with affordable and efficient miniature LED-photodiode devices, we reach an ultralow limit of detection well below the ppm level.