ORIGINAL PAPER Flow Injection Spectrofluorimetric Determination of Iron in Industrial Effluents based on Fluorescence Quenching of 1-Naphthol-2- Sulfonate Hossam E. M. Sayour & Taha M. A. Razek & Karima F. Fadel Received: 15 August 2010 / Accepted: 29 December 2010 # Springer Science+Business Media, LLC 2011 Abstract A sensitive and selective spectrofluorimetric method has been developed for flow injection analysis (FIA) of iron(III) based on its fluorescence quenching effect on the water soluble 1-naphthol-2-sulfonate. The fluores- cence emission spectra were collected with excitation at 283 nm. The emission peaks of the neutral and anionic forms of 1-naphthol-2-sulfonate as well as the band area were found to decrease linearly with iron(III) concentra- tions over the range 0.1–18 μg ml -1 and a detection limit of 3.4 ng ml -1 (emission at 349 nm) with FIA. Possible interferences from different cations and anions, which could affect the analytical response, are evaluated and showed the high selectivity of the method. The effect of solution pH and 1-naphthol-2-sulfonate concentration were examined and the reaction conditions are optimized. The method is successfully applied to determine iron(III) in industrial effluents from different sources without any complications with recoveries of almost 100% with both manual and flow injection methods. Results were found to be very consistent with those obtained using atomic absorption spectrometry. Keywords Fluorescence quenching . Flow injection . Naphthol derivatives . Determination of iron(III) . Industrial effluents Introduction Iron is found in many natural and treated waters. It is an objectionable constituent in both domestic and industrial water supplies. Iron is not preferable to be present in raw materials required for the manufacture of glass, crystal and ceramics (porcelain, alumina refractories and refractory mortars) in which iron concentration may be at maximum of 0.1%. High concentrations in surface waters can indicate the presence of industrial effluents or runoff from other operations. Because of this, iron determination in environ- mental and industrial samples with such low levels precisely, rapidly and accurately is of paramount impor- tance. Many analytical methods were reported for the determination of iron; they are inductively coupled plasma mass spectrometry [1], atomic absorption spectrometry [2, 3], potentiometry [4], ion chromatography [5], chemi- luminescence [6], anodic stripping voltammetry [7] and spectrophotometry [8, 9]. However, reported spectrofluori- metric methods for the determination of iron(III) are rare. These methods depends mainly either on detecting the fluorescence emitted up on the formation of a metal chelate (direct fluorimetry) or following fluorescence quenching induced by the presence of the metal cation. In direct fluorimetry, some fluorogenic compounds were used for the determination of iron [10–16]. These methods suffer from different drawbacks as pre-treatment step such as pre- reduction, occurrence of metal interference or addition of surfactant as fluorescence enhancer. In fluorescence quenching methods, some other fluorogenic compounds H. E. M. Sayour Clinical Chemistry Unit, Department of Chemistry and Nutritional Deficiency Disorders, Animal Health Research Institute, Dokki, Giza 12618, Egypt T. M. A. Razek (*) Department of Environmental basic science, Institute of Environmental studies and Research, Ain Shams University, Abbassia, Cairo 11566, Egypt e-mail: tahaelsabbagh@yahoo.com K. F. Fadel Central lab of Ain Shams University, Abbassia, Cairo 11566, Egypt J Fluoresc DOI 10.1007/s10895-010-0821-z