A flow-through fluorescent sensor to determine Fe(III) and total inorganiciron

A flow-through fluorescent sensor for the consecutive determination of Fe(I II) and total iron is described. The reactive phase of the proposed sensor, which has a high affinity for complexed Fe(III), consists of pyoverdin imm obilized on controlled pore glass (CPG) by covalent bonding. This pigment s electively reacts with Fe(III) decreasing its fluorescence emission. Total inorganic iron is determined as Fe(III) after on-line oxidation in a mini-c olumn containing persulphate immobilized on an ion exchange resin. The deve loped method allows the determination of Fe(III) in the 3-200 mu g l(-1) ra nge. The relative standard deviations of 10. determinations of 60 mu g l(-1 ) of Fe(III) and 20 mu g l(-1) of Fe(III) + Fe(II) are 3 and 5%, respective ly. The sensor has been satisfactorily applied to speciate iron in syntheti c, tap and well waters and wines. There were no significant differences for total inorganic iron determination between this new method and the atomic absorption spectroscopy reference method at the 95% confidence level. The s ensor allows the concentration of Fe(II) to be calculated as the difference between total inorganic iron and Fe(III). The lifetime of the sensor is at least 3 months in continuous use or the equivalent of 1000 determinations. (C) 2000 Elsevier Science B.V. All rights reserved.