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1.4 CHEMICAL SCIENCES, Analytical chemistry
Bromocresol Purple,(BCP) cast onto an acetate sheet, was used to sense ammonia. This simple layer responded reversibly to a low concentration ( 15 ppm) of ammonia in the presence of water vapour. The BCP solution was spincoated on an acetate sheet from a solution in dichloromethane. This layer was exposed to nitrogen and NH3/H2O vapour in quick succession. The colour change occurred from yellow to purple rapidly in the solid state. The λmax for the neutral ( acid) form of the BCP was found to be 435 nm and the λmax for the dianion ( base form) of the BCP was found to be 610 nm A mechanism previously predicted theoretically was confirmed using FTIR identifying the presence of a peak associated with a carbonyl in the dianion form.
Cassidy, J.F. et al. (2020) An Ammonia Sensor Using an Unadorned Bromocresol Layer, International Journal of Environmental Analytical Chemistry. DOI: 10.1080/03067319.2020.1807975