Thermodynamics and Kinetics of the Complexation Reaction of Lead by Calix‐DANS4 |
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Authors: | Dr Ting Wu Dr Isabelle Leray Dr Valérie Génot Jean Pierre Lefèvre Alexandre Korovitch Dr Nguyêt‐Thanh Ha‐Duong Dr Jean‐Michel El Hage Chahine Prof Jacques Alexis Delaire |
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Institution: | 1. PPSM, ENS de Cachan, CNRS, UniverSud Paris, 61 avenue du Président Wilson, 94230 CACHAN (France), Fax: (+33)?147402454;2. ITODYS, Université Paris‐Diderot, CNRS, Batiment Lavoisier, 15 rue Jean‐Antoine de Ba?f, 75205 Paris Cedex 13 (France) |
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Abstract: | The thermodynamics and kinetics of the complexation reaction between lead ions and the fluorescent sensor Calix‐DANS4 are determined to optimize the geometry of the microreactor used for the flow‐injection analysis of lead and to tune the working conditions of this microdevice. Under our experimental conditions (pH 3.2, low concentration of Calix‐DANS4) the 1:1 Pb2+‐Calix‐DANS4 complex is predominantly formed with a high stability constant (log K1:1=6.82) and a slow second‐order rate constant (k=9.4×104 L mol?1 s?1). Due to this sluggish complexation reaction, the microchannel length must be longer than 130 mm and the flow rate lower than 0.25 mL h?1 to have an almost complete reaction at the output of the microchannel and a high sensitivity for the heavy metal detection. After determination of the values of the reaction times in our different microdevices, it is possible to simulate the calibration curves for the fluorimetric detection of lead under different conditions. An original method is also presented to determine mixing times in microreactors. |
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Keywords: | fluorescent probes kinetics lead microreactors stopped‐flow kinetics |
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