INVESTIGATIONS ON SELECTED REAGENTS LEADING TO DEVELOPMENT OF OPTICAL CHEMICAL SENSOR FOR ORGANIC VAPOUR POLLUTANTS

This thesis presents investigations carried out in order to evaluate the suitability of Cobalt tetra-methoxyphenyl porphyrin (CoP(ph-OMe)4) and Bis[N,N-bis(carboxymethyl)amino methyl]fluorescein (FLXN) as sensing reagents for the organic pollutants namely; anthracene (ANTH), benzo(a)pyrene (BaP), pyrene (PRN) and pyridine (Py). Analyses leading towards development of a fluorescence based fibre optical chemical sensing system (FBFOCS) has been carried out. The mechanism is based on monitoring the fluorescence properties of thin solid film of a chemical transducer with changing concentration of the organic pollutants selected for this research. Immobilization of thin films of these sensing macromolecules in Poly-dimethyl Siloxane (PDMS) matrix has been successfully achieved. These solid thin films are prepared for the purpose of using them as optical chemical sensing systems fora fore mentioned organic pollutants. A Flow cell with compartment (sensing platform) for holding the sensing films and enabling pumping in and out of the organic pollutant vapours have been fabricated for this research. Absorption and fluorescence measurements performed on these films when subjected to Polycyclic-Aromatic Hydrocarbons (PAHs) and also to pyridine (Py) vapours have illustrated that, these organic pollutants change the way the sensing molecules emit and absorb radiant energy from the electromagnetic spectrum.
Evaluated LOQ and MDL for both sensing molecules with the pollutants, range from 0.002 to 171.32 μg/L (LOQ) and 0.0001 to 6.0 μg/L (MDL). These values are lower than Permissible Exposure Limits (PEL), which range from 0.1 to 0.2 mg/L, set by international environmental pollution monitoring agencies.
Therefore these reagents have been evaluated and can be recommended for development as viable sensors for organic pollutants under this study.