Photophysical studies of N-Acetyl Tryptophanamide (NATA) with urea derivatives were carried out in aqueous solution. The urea derivatives were categorised into symmetrical and unsymmetrical urea derivatives. Addition of urea derivatives result in a significant change in the absorbance maximum of NATA. Interestingly, the addition of urea and N, N’-1, 3 dimethylurea (DMU), a symmetrical urea derivative results in a fluorescence enhancement whereas an unsymmetrical urea derivative like N-butyl urea results in a fluorescence quenching. On the contrary, N-methyl urea (MU) exhibits no significant change in the fluorescence intensity, whereas N-ethyl urea (EU) results in a fluorescence enhancement to a considerable extent. The variation in excited state properties of NATA with urea derivatives are correlated to the variation in the excited state dipole moment of the indole moiety microenvironment. Various hydrogen-bonding arrangements exits between NATA and urea derivatives and this is correlated to the shift in the emission maxima towards the red region. NATA exhibits a single exponential decay and the fluorescence lifetime in aqueous solution is 3.0 ns. Addition of urea derivatives results in a significant increase in the fluorescence lifetime irrespective of the nature of the urea derivatives. Butyl Urea(BU), which displays a red shift accompanied with fluorescence quenching of NATA exhibits contrasting properties compared to other urea derivatives is established through fluorescence spectral studies.

This study assessed the effect of cabamate and pyrethroid pesticide residues from agricultural activities on fish samples from the Owena river, Ondo State, Nigeria. The aim of the study was to assess the bioaccumulation and the health risk implication of consuming polluted fish from the river. The fish samples were extracted with an ultrasonic bath extractor and the extracts were analysed with a gas chromatograph coupled to a mass spectrometry detector. The mean level of carbamate pesticide contaminants in dry season for Oreochromis niloticus, Gvmnarchus niloticus, S. galileaus and Claria gariepinus are 0.25±0.02µg/g, 0.24±0.01µg/g, 0.30±0.03µg/g and 0.26±0.02µg/g respectively. Their level in wet season for Oreochromis niloticus, Gvmnarchus niloticus, S. galileous, Clarias anguillaris and Parachanna obscura were 0.11±0.03µg/g, 0.21±0.02µg/g, 0.10±0.04µg/g, 0.14±0.03, 0.13±0.03µg/g and 0.12±0.05 µg/g respectively. The level of pyrethroid contaminants in dry season for Oreochromis niloticus, Gvmnarchus niloticus, S. galileaus and Claria gariepinus are 0.82±0.79µg/g, 0.53±0.04µg/g, 0.39±0.04µg/g and 1.91±1.99µg/g respectively. Their level in wet season for Oreochromis niloticus, Gvmnarchus niloticus, S. galileous, Claria gariepinus. Clarias anguillaris and Parachanna obscura were 0.22±0.05µg/g, 0.18±0.06µg/g, 0.13±0.05µg/g, 0.19±0.10, 0.12±0.02µg/g and 0.22±0.04 µg/g respectively. The concentrations of some of pollutants in the fish samples were higher than the FAO/WHO maximum residue limit of 0.5µg/g. The health risk evaluation indicates that there is no health risk. Nevertheless, strict monitoring of the handling and usage of these chemicals should continue to be enforced strictly by Nigerian government.