Spectrophotometric detection of pentachlorophenol (PCP) in water using water soluble porphyrins

The spectrophotometric properties of porphyrins are altered upon interaction with chlorophenols and other organochlorine pollutants. Meso-tetra (4-sulfonatophenyl)porphyrin (TPPS), zinc meso-tetra (4-sulfonato phenyl) porphyrin (Zn-TPPS), monosulfonate tetraphenylporphyrin (TPPS1), meso-tri (4-sulfonatophenyl)-mono(4-carboxyphenyl)porphyrin (C1TPP), meso-tetra (4-carboxyphenyl) porphyrin (C4TPP), and copper meso-tetra (4-carboxyphenyl)porphyrin (Cu-C4TPP) in solution exhibit a broad absorbance in the range of 400–450 nm Soret region. The interaction of the above mentioned porphyrins in solution with pentachlorophenol induces a red shift in the Soret spectrum with absorbance losses at 413, 418, 403, 405, 407, and 404 nm, respectively, and the appearance of new peaks at 421, 427, 431, 416, 417, and 416 nm, respectively. The intensity of the Soret spectral change is proportional to the pentachlorophenol concentration with a detection limit of 1, 0.5, 1.16, 1, 0.5, and 0.5 ppb, respectively. The interaction of (C4TPP) and (Cu-C4TPP) in solution with PCP is dependent on concentration; for concentrations less than 4 ppb the dependence was log-linear. However, for concentrations greater than 4 ppb the relation was linear. results suggest the potential for development of spectrophotometric chemosensor for PCP residues in water with detection limits less than US EPA maximum contaminate level (MCL) of 1 ppb.