The photochemistry of free-base meso-tetraphenylporphyrin linked to methyl viologen via an alkoxy chain (n = 3) at the ortho, meta or para-position of one meso-phenyl group, in Triton X-100 micellar aqueous solutions is reported. The appended viologen does not quench the porphyrin fluorescence nor its triplet excited state due to the different solubilization of both parts of the molecule in the medium where the porphyrin ring resides in the hydrophobic phase and the alkoxy linker protrudes into the rather diffuse outer phase of detergent oxyethylene units, while the viologen moiety penetrates into the aqueous layer. However, laser flash photolysis measurements show that in the presence of nicotinamide dinucleotide, NADH, the porphyrin ring is reduced to phlorin due to the penetration of NADH into the organic phase. For porphyrin-tetraviologen in which a viologen molecule is linked to each of the porphyrin meso-position via alkoxy chain, fluorescence quenching could be achieved. The values of the quenching efficiency are high (94% in acetonitrile) compared to intramolecular quenching and are dependent upon the solvent viscosity.
Iron was determined spectrophotometrically in water samples and boiler scale by extracting the ion-associate formed between iron(II)-Bathophenanthroline cationic complex and Eosin anion into chloroform. The ion-associate was formed in the pH range 3.6 -5.2. The method was highly sensitive and selective. The extracted species had an apparent molar absorptivity of (1.32±0.02)X1051 mol-1 cm-1 at 542 nm with a sensitivity index of 0.42 ng cm 2. Beer's law was valid up to 0.42 µg ml-1 of iron in the aqueous phase. The composition of iron : Bathophenanthroline : Eosin ionassociate was 1: 3 : 2. EDTA was used to mask Cd2+, Cot, Cue, Ni2+ and Zn2+.
KeywordsIron determination , bathophenanthroline, Eosin, waterThe recommended ASTM1 spectrophotometric method for iron determination in water is based on reaction with 1,10-phenanthroline [E(510 nm)= 1.1X1041 mol-1 cm].However some metal ions and anions interfered when present in considerable excess. Moreover, bathophenanthroline reacts with iron(II) to form a sparingly soluble complex extractable in ethanolchloroform or isopentyl alcohol),2 The selectivity of this method is similar to that of 1,10-phenanthroline with twice the sensitivity [E(533 nm)=2.24X1041 mol-1 cm']. Tetlow and Wilson3 adapted the bathophenanthroline method to determine iron in boiler-feed water.Recently, the sensitivity of the spectrophotometric methods for iron determination has been markedly improved by use of surfactants and micellar systems4-16, or by forming ion-association complexes.1'-22 However, some of these methods lack selectivity or require close control of experimental conditions. The present work reports an extraction-spectrophotometric method for iron(II) determination using bathophenanthroline as primary ligand and Eosin anion as the counter ion. The developed procedure is highly sensitive and has the advantage of being selective and more convenient for general laboratory use. The method has been successfully used to determine iron in water samples (drinking-water, river-water, boiler-feed water and waste water) and boiler scale.
ExperimentalElmer Lambda 3B spectrophotometer with 1-cm quartz cell. A Schot Gerate pH-meter equipped with a combined glass-calomel electrode was used for pH adjustments.A stock solution of iron(III) contaning 0.56 mg ml-1 of iron (ca. 0.01 M) was prepared by dissolving ammonium iron(III) sulfate dodecahydrate in 0.1 M sulfuric acid and was standardized by titration with EDTA at pH 2 -3 (Variamine Blue B indicator).23 Working solutions were prepared by appropriate dilution of the stock solution.Hydroxylamine hydrochloride and sodium acetate solutions of 10(m/ v)% concentration were prepared and further purified by adding bathophenanthroline and extracting the traces of iron(II) complex into chloroform as reported previously.24 A 0.1(m/v)% ethanolic bathophenanthroline solution and 0.1(m/v)% aqueous Eosin (sodium salt) solutions were also prepared.
ProcedureAn aliquot of the acidic sample solution containing up to 8.4 µg of iron(II or III) was placed in a 50-ml s...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.