Optical detection of bromide ions using Pt(II)-5,10,15,20-tetra-(4-methoxy-phenyl)-porphyrin

Abstract

Bromide ions are present in many environments, such as sedative drugs, methyl-bromidetreated vegetables and seawater. Excess bromide in humans interferes with iodide metabolism and is considered toxic. The need for fast and inexpensive methods for bromide detection is of interest. Spectrophotometric detection methods provide accurate and sensitive results. The well-known ability of metalloporphyrins to bind anionic ligands to the central metal ion has been exploited. The changes in the optical properties of Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) under the influence of bromide ions allowed us to achieve a fast, simple and reliable UV-vis spectrophotometric method of detection with a detection limit of 2.5 × 10-8 M and a good confidence coefficient: 99.05%. The potential interfering ions, such as Cl-, I-, NO2-, NO3-, SCN-, SO32-, SO42- and PO43- of 100-fold higher and Cl- and R-S- of 1000-fold higher concentrations in the mixture as compared to the determined concentration of bromide ions (c = 10-5 M), were tested and did not influence the results. The behavior of the sensitive porphyrin in various pH media was investigated in order to determine their influence upon the bromide detection capacity.