title: The use of anion-exchange disks in an optrode coupled to a multi-syringe flow-injection system for the determination and speciation analysis of iron in natural water samples.
abstract: A combination of multi-syringe flow-injection analysis (MSFIA) technique with an optical fibre reflectance sensor for the determination of iron in water samples has been developed in this work. Anion-exchange solid phase extraction (SPE) disks have been used as solid phase. Ammonium thiocyanate has been chosen as chromogenic reagent for Fe(III). The complex Fe[SCN](6)(3-) is retained onto the SPE disk and spectrophotometrically detected at 480nm. The complex is eluted with 0.25moll(-1) hydrochloric acid in 75% ethanol. Total iron can be determined by oxidising Fe(II) to Fe(III) with hydrogen peroxide. A mass calibration was run within the range of 0.4-37.5ng. The detection limit (3s(b)/S) was 0.4ng. The repeatability (RSD), calculated from 9 replicates using 0.5ml injections of a 25microgl(-1) concentration, was 3.6%. The repeatability between five anion-exchange disks was 5.4%. An injection throughput of 7 injections per hour for a sampling volume of 1ml has been achieved. The applicability of the proposed methodology in natural water samples has been proved. The properties of anion-exchange and chelating SPE disks have been studied and compared.
authors.affiliation: Department of Chemistry, University of the Balearic Islands, Palma de Mallorca, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Pons
authors.forename: Rafael
authors.initials: R
authors.lastname: Forteza
authors.forename: Víctor
authors.initials: V
authors.lastname: Cerdà