AN OPTOCHEMICAL AMMONIA SENSOR-BASED ON IMMOBILIZED METALLOPORPHYRINS

An optochemical sensor to determinate ammonia has been developed by immobilizing metalloporphyrins in appropriate polymeric membranes. The detection of ammonia is based on changes of UV/VIS absorbance spectra occurring by coordination of gas molecules to the central metal ion of the immobilized dye. Effects of porphyrin derivatives, metal ions and immobilization matrices on sensor properties were investigated. The Mn(II) complex of 5,10,15,20-tetra(phenyl)porphyrin was found to show a high sensitivity to ammonia when immobilized in membranes of nitrocellulose. The detection limit for ammonia in synthetic air was 630 ppb (440 mug/m3). The response time of the sensor was in the range 2-4 min and the reaction with ammonia was reversible.