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Item Simultaneous detection of Pb(II) and Cd(II) in aqueous solutions by UV-visible spectrophotometry(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Dikella, D. G. T. N.; Rajapakse, C. S. K.The pollution of water resources due to disposal of metals, especially heavy metals is one of the most concerned environmental issues in the current world. Therefore, detection of these heavy metal ions with rapid, sensitive and accurate analytical tools is important. In recent years, water soluble porphyrins, macrocyclic compounds have gained growing interest as colorimetric agents for heavy metal detection by UV-VIS spectrophotometry. Porphyrins are highly sensitive to metal ions and display new Soret band (~ 400 nm) as well as minor Q bands (500–700 nm) upon metal ion chelation. This property has been widely used for detecting heavy metal ions in aqueous solutions. In this work, the influence of pH, water hardness (Ca(II)) and presence of other foreign ions (Mg(II), Co(II), Al(III), Cr(III), Fe(III), Ba(II), K(I), Mn(II), Sn(II), Ni(II), Zn(II), Bi(III)) for simultaneous detection of Pb(II) and Cd(II) by a porpyrin; 5, 10, 15, 20-tetrakis (1-methyl-4-pyridinio) porphyrin tetra (p-toluenesulfonate); (TMPyP) under the selected experimental conditions were investigated. TMPyP displayed a characteristic Soret band in the UV-Vis spectrum at 422 nm. Upon addition of Pb(II) and Cd(II) into TMPyP, the band at 422 nm was disappeared and new Soret bands were appeared at 474 nm and 444 nm, respectively indicating that these characteristic absorption bands, attributed to corresponding Metal(II)-TMPyP complexes. The lower detection limit (LOD) for Pb(II) and Cd(II) with TMPyP was found to be 0.02 mg/L and 0.01 mg/L, respectively which are considerably below the maximum permissible levels for wastewater discharge according to WHO guidelines. The best pH range for simultaneous detection of Pb(II) and Cd(II) was found to be pH 7 to 9. The water hardness (Ca(II)) and the presence of other foreign ions also had no significant effect on the simultaneous detection of Pb(II) and Cd(II) ions in aqueous solutions. It was possible to remove TMPyP complexes as well as unbound TMPyP successfully using chitosan before discharging the analyzed solutions. The results revealed that the TMPyP can function as a single optical sensor capable of detecting Pb(II) and Cd(II) simultaneously in aqueous solutions in the pH range 7-9.Item A simple and rapid UV-Visible spectrophotometric method for determination of Mercury (II) using TMPyP in aqueous solutions.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Hettiarachchi, A. H .P.; Rajapakse, C. S. K.Even though Mercury and its compounds are known to be extremely toxic they are widely distributed in the environment. The main sources of mercury pollution are coal burning power plants, paper, plastic, electrical, paint, and pharmaceutical industries. Uses of mercury as pesticides also add mercury to the environment. Several analytical methods are available to detect heavy metal ions in environmental water samples and biological samples. However, in recent years significant attention has been focused on porphyrins, as the sensitive sensing reagents for spectrophotometric determination of several metal ions. In this study, a simple, rapid and considerably sensitive UV-Visible spectrophotometric method was developed for determination of Hg(II) using, 5, 10, 15, 20-Tetrakis (1-methyl-4-pyridinio) porphyrin tetra (p-toluenesulfonate); (TMPyP) as the sensing reagent. The effects of pH, water hardness and presence of other metal ions such as Cd(II), Cr(III) and Pb(II) for Hg(II) detection were also examined. Upon addition of Hg(II) ions into an aqueous solution of TMPyP, a new absorption band (Soret band) appeared at 458 nm indicating that, this characteristic absorption band, attributed to Hg(II)-TMPyP complex can be used as a diagnostic absorption for Hg(II) ions. The reaction was very fast and constant absorbance was achieved within 1 min and the system obeys Beer’s law for concentration range of Hg(II) between 0.005 mg L-1 and 70 mg L-1. The detection limit for Hg(II) with TMPyP was determined to be 0.003 mg L-1 which is below the maximum permissible limit (0.005 mg L-1) for wastewater discharge according to EPA effluent discharge standards. The best pH range for Hg(II) detection was found to be pH 7-12. Hg(II) detection was not affected by water hardness. The presence of Mg(II), Cd(II), Cr(III) and Pb(II) ions over a concentration range of 0-100 mg L-1 also had no significant effect on the detection of Hg(II) ions. It was possible to successfully remove Hg(II) - TMPyP complex as well as unbound TMPyP from the aqueous solutions using chitosan, before discharging the analyzed aqueous samples. These results indicated that, TMPyP can be used as a promising optical chemical sensor for the detection of Hg(II) in aqueous solutions with satisfactory sensitivity and selectivity.