To determine the octanol–water partition coefficient (logKow or logD), a microfluidic method is developed to reduce time and coast of analyze. A double Y serpentine microfluidic chip is fabricated used soft lithography facilities. To generate a biphasic parallel flow, hydrophilic microchannels walls are generated by oxygen plasma treatment. Epifluorescence microscopy is used to measure the intensity of fluorescence molecules in microchannel. Using microfluidic parallel diluter this intensity show a strong linear correlation with molecule concentration in solution. The equilibrium between phases is reached in less than 5s. To validate this microsystem, we have determined the logD of fluorescein natrium molecule. The obtained results compare well with previous measurements using traditional shake-flask or microfluidic drops flow methods, with a relative difference to the literature less than 3%. Rapid microfluidic partition coefficient determination is useful for studying liquid–liquid partition of organic pollutant.

Aqueous solubility and vapor pressures of 1,2,3,4-dibenzanthracene and 1,2,5,6-dibenzanthracene were determined using dynamic saturation methods. For the two isomers, aqueous solubility is in the range between 10−10 and 10−2 in molar fraction corresponding to temperature between 298.15 and 338.15K. Vapor pressures of the pure solutes range from 10−5 to 80Pa. Prior to the study of the two dibenzanthracenes and in order to check the experimental procedures, solubility of fluoranthene (between 298 and 338K) and vapor pressures of phenanthrene and fluoranthene (between 300 and 470K) were measured.From aqueous solubility data coupled with the vapor pressures of the pure solutes, partition coefficient air-water, KAW, and Henry’s constant, KH, of environmental relevance were calculated.

This paper describes two configurations that integrate electrochemical detection into microfluidic devices. The first configuration is a low-cost approach based on the use of PCB technology. This device was applied to electrochemiluminescence detection. The second configuration was used to carry out amperometric quantification of electroactive species using a serial dilution microfluidic system.

This paper describes a microfluidic device fabricated in poly(dimethylsiloxane) that was employed to perform amperometric quantifications using on-chip calibration curves and on-chip standard addition methods. This device integrated a network of Au electrodes within a microfluidic structure designed for automatic preparation of a series of solutions containing an electroactive molecule at a concentration linearly decreasing. This device was first characterized by fluorescence microscopy and then evaluated with a model electroactive molecule such as Fe(CN(6))(4-). Operating a quantification in this microfluidic parallel approach rather than in batch mode allows a reduced analysis time to be achieved. Moreover, the microfluidic approach is compatible with the on-chip calibration of sensors simultaneously to the analysis, therefore preventing problems due to sensor response deviation with time. When using the on-chip calibration and on-chip standard addition method, we reached concentration estimation better than 5%. We also demonstrated that compared to the calibration curve approach, the standard addition mode is less complex to operate. Indeed, in this case, it is not necessary to take into account flow rate discrepancies as in the calibration approach.

This paper presents an inexpensive approach of implementing electrochemiluminescence (ECL) detection for microfluidic analytical systems. It consists in using printed circuit board (PCB) technology to design electrodes and sealing the epoxy substrate with a transparent microfluidic structure in polymer for ECL detection and system integration. A pair of PCB electrodes (10 mm(2)) and an ECL microfluidic device are designed and fabricated. They are tested via luminol ECL detection to quantify H2O2. Characterization of the PCB electrodes is performed via the determination of the optimum potential (0.7 V vs. Ag/AgCl) to trigger luminol oxidation. Electrode potential is square-wave modulated from 0 to 0.7 V at a minimum period of 17 s. Measurements of on/off modulated ECL signals for different H2O2 concentrations are carried out to establish their relationship. The obtained results show a 50-nM detection limit at a signal-to-noise ratio (SNR) equal to 3 and a linear range extending up to 0.1 mM in batch or in microfluidic conditions. The detection volumes for these two systems are 2 ml and 4 mu l, respectively. (c) 2007 Elsevier B.V. All rights reserved.

We present an instrumental development to implement electrochemiluminescence (ECL) microanalysis using printed circuit board (PCB) technology. PCB gold macro- (10 mm 2 ) and micro- (0.09 mm 2 ) electrodes and two ECL microfluidic devices are designed, fabricated and tested via luminol ECL detection. Potential modulation is performed between 0.7 and 0 V vs. Ag/AgCl for luminol oxidation, thus giving rise to on/off ECL responses in the presence of hydrogen peroxide. Synchronous detection is adopted to allow weak ECL signal recovery at a very low signal-to-noise ratio (SNR). The detection limit obtained with the two ECL microfluidic devices is 50 nM and 100 nM H 2 O 2 for macroelectrodes and microelectrodes, respectively.

This work investigates the efficiency of a chaotic micromixer using thermal lens spectrometry. The outlet of the mixing device was connected to a thermal lens detection head integrating the probe beam optical fibers and the sample capillary. The chaotic micromixer consisted of a Y-shaped poly(dimethylsiloxane) (PDMS) microchip in which ribbed herringbone microstructures were etched on the floor of the main channel. Due to the solvent composition dependence of the thermal lens response, the photothermal method was shown to be highly sensitive to nonhomogeneous mixing compared to fluorescence detection. The apparatus was applied to the determination of Fe2+ with 1,10-phenanthroline using flow injection analysis; a limit of detection of 11 microg L(-1) of iron was obtained.