1 Spectroscopy using Optical Fibres In the marine Environment : the S.O.F.I.E. project Seawater analysis for research and monitoring purposes is a challenging task because many constituents of interest are to be measured at trace level in a very complex matrix. Classical way of performing chemical analyses in seawater is to take statistically spatial and temporally distributed samples followed by laboratory analyses on board a ship or on shore. Alteration of the sample upon transport and storage is one of the main flaws inherent to this sampling approach. The objective of S.O.F.I.E. (joint European project) is the development of a modular all-fiber-optic measurement device for real-time and in- situ monitoring of hazardous chemicals in the marine environment. 2 Luminescence optode A sensor system has been developed for the in-situ detection of a selection of heavy metals ions (Pb 2+, Cu 2+, Hg 2+, Cd 2+ ) in seawater. The optical sensing is based on the continuous monitoring of the fluorescence spectrum of an immobilized metal-ion-sensitive-dye system. The metal ions diffusing in the layer are chelated and the fluorescence properties of the dye are changed : the intensity of the fluorescence level can therefore be directly link to the concentration of the chosen analyte(s) for alarm purposes. 4 Used Sensing technique : Ion-Pair This class of sensor generally consists of a plasticised PVC membrane with three main components : an ion-selective ligand, a pH indicator and a lipophilic additive to ease the transport of charge. 3 Used Sensing technique : Fluoroionophore Reagents such as the modified hydroxyquinoline AHQ have been shown to display fluorescence variations resulting from the formation of complexes of the metal ion and are therefore been used in sol-gel membrane. 5 Conclusion Considering the two systems studied, sensitivity towards a selection of metal ions have been achieved in the ppt to ppb range and reversibility has been observed. Nevertheless, it appears that the influence of process parameters dramatically alters the properties of the membrane as lifetime, response time, reversibility and sensitivity of the membrane are intrinsically link ; it therefore is difficult to achieve good repeatability of the measurements and does not allow yet their use for in-situ conditions. For electroneutrality reasons, when the ligand carries a metal ion M + in the membrane, a proton is co-extracted, which protonates the indicator dye, which results in a change in the optical properties. This class of sensor generally consists of a plasticised PVC membrane with three main components : an ion-selective ligand, a pH indicator and a lipophilic additive to ease the transport of charge. Dextran (polysaccharide) derivatives efficiently reduces the leaching of the linked dye and sensitivity towards Pb 2+ as been observed in the ppt range but the membrane’s lifetime (10% of leaching per hour) does not allow a long-term reversible use. Pb 2+ : mg/l no metals Pb 2+ : mg/l t=0h, no metals t=2h, no metals t=1h, Pb 2+ : mg/l t=3h, Pb 2+ : mg/l The covalent binding of AHQ on sol-gel is effectively avoiding the leaching out of the dye, a fully reversible membrane is therefore prepared and sensitivity towards Cd 2+ was observed in the 100ppm range. Nevertheless, the ageing of the membrane dramatically increases the insensitivity towards metal ions and therefore makes the sensor obsolete in-situ for long-term use. PVC / DOS / Lead ionophore II / Oregon Green Dextran ex =473 nm Other used matrices included Nafion (cationic exchanger, anionic excluder), pHEMA (hydrogel) and Sol-Gel (glass-like polymer) but all our attempts to use Ion-Pair in a material other than PVC has been unsuccessful. pH=7.4 Optical Sensing of Heavy Metal Ions in Seawater using Fluorescence X. Poteau, C. Haslinger, T. Glanzmann, B.D.MacCraith School of Physical Sciences/Optical Sensor Laboratory/NCSR Dublin City University Dublin 9-Ireland