Cyclodextrin-enhanced photo-induced fluorescence of -fluvalinate, molecular modelling of inclusion complexes and determination in natural waters.

The effect of adding organized supramolecular systems such as β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) on the photochemically-induced fluorescence (PIF) spectral properties of -fluvalinate (TFV) in aqueous solutions was examined. The influence of pH, UV irradiation time and photoproduct stability on the cyclodextrin-enhanced photochemically-induced fluorescence intensity was also investigated. The spectral changes associated with the inclusion process yielded values for the formation constants of TFV inclusion complexes between 450 and 640 M, which were calculated using the nonlinear iterative regression approach least squares.

Direct Spectrofluorimetric Method for the Analysis of Carbofuran and Fluometuron in Senegalese Natural Waters.

In this work, analytical study of carbofuran (CAF) and fluometuron (FLM) pesticides was carried out using direct spectrofluorimetric method in various solvents. Results showed that CAF and FLM are naturally fluorescent in all solvents under study including organic (MeOH, MeCN, DMF) and aqueous micellar one (CTAC, SDS, Brij-700). For the analysis of FLM, CTAC give the best fluorescence signal enhancement.

Analysis of non-native fluorescent pesticides by thermo-induced and photo-induced fluorescence, a comparative study.

This paper compares the performance of three analytical methods for the determination of pesticides in natural waters. As many pesticides are non-fluorescent, they are transformed into highly fluorescent by-products in two ways: elevated temperature in an alkaline medium (thermo-induced fluorescence - TIF); or UV irradiation in water (photo-induced fluorescence - PIF). The first method studied uses TIF, the second one uses PIF and the third one uses an automatic sampling and analysing PIF system.

High sensitivity on-site early warning system monitoring of pesticides by photo-induced fluorescence.

This paper describes the prototype of an on-site High Sensitivity Early Warning Monitoring System, using Photo-Induced Fluorescence, for pesticide monitoring in natural waters (HSEWPIF). To obtain a high sensitivity, the prototype was designed with four main features. Four UV LEDs are used to excite the photoproducts at different wavelengths and select the most efficient one.

Micellar enhanced photo-induced fluorescence and absorbance for the development of an on-site early warning water quality monitoring system for pesticides.

This paper describes two prototypes of an on-site Early Warning Water Quality Monitoring System (EWWQMS) for pesticide quantification in natural waters. As many pesticides are non-fluorescent, the EWWQMS setup uses UV photoconversion to form highly fluorescent photoproducts. To enhance sensitivity, the two prototypes use micellar-enhanced fluorescence with surfactant (cetyl trimethyl ammonium chloride) in aqueous solution.

Alternative to High Pressure Mercury Vapor Lamp for Photo Induced Fluorescence Analytical Methods; Application to the Determination of Pesticides in Water.

The photo-induced fluorescence method is often applied to determine non-native fluorescent compounds. It typically uses UV irradiation from a high pressure mercury vapor discharge lamp to create photo-induced fluorescent compounds, which are then quantified by fluorescence spectroscopy. However, these mercury lamps require a high-voltage power supply and may accidentally induce electric shocks and the release of mercury vapors.

Development of an on-site early warning water quality monitoring system for pesticide detection by absorption and photo-induced fluorescence.

This paper describes prototypes of an on-site early warning water quality monitoring system (EWWQMS) for pesticide quantification in natural waters by fluorescence and absorbance. As many pesticides are not naturally fluorescent, this EWWQMS uses UV irradiation to transform these compounds into highly fluorescent photoproducts and obtain sufficient sensitivity. To obtain a better specificity, the system uses four UV LEDs at different wavelengths to excite the fluorescent photoproducts.

Analysis of Oxadiazon Herbicide in Natural Water Samples by a Micellar-enhanced Photo-induced Fluorescence.

A micellar-enhanced photo-induced fluorescence (ME-PIF) method was developed to analyze, for the first time, oxadiazole herbicide (namely oxadiazon) in natural water samples. Photo-conversion under UV irradiation of the herbicide into strongly fluorescent photoproducts was performed in aqueous solution and in the presence of two surfactants, cetyltrimethylammonium chloride (CTAC) or Tween 20, at micellar concentrations. The ME-PIF parameters were optimized.

Combination of photoinduced fluorescence and GC-MS for elucidating the photodegradation mechanisms of diflubenzuron and fenuron pesticides.

Diflubenzuron (DFB) and fenuron (FEN) are benzoylurea and phenylurea pesticides, widely used in Senegal, that do not exhibit any natural fluorescence, but can be determined by means of photoinduced fluorescence (PIF) methods. Photodegradation of DFB and FEN yielded a number of fluorescent and non-fluorescent photoproducts. For both pesticides, at least 10 photoproducts were detected and identified by gas chromatography-mass spectrometry (GC/MS).

Development of online automatic detector of hydrocarbons and suspended organic matter by simultaneously acquisition of fluorescence and scattering.

Permanent online monitoring of water supply pollution by hydrocarbons is needed for various industrial plants, to serve as an alert when thresholds are exceeded. Fluorescence spectroscopy is a suitable technique for this purpose due to its sensitivity and moderate cost. However, fluorescence measurements can be disturbed by the presence of suspended organic matter, which induces beam scattering and absorption, leading to an underestimation of hydrocarbon content.

Biophysical properties of cationic lipophosphoramidates: Vesicle morphology, bilayer hydration and dynamics.

Cationic lipids are used to deliver genetic material to living cells. Their proper biophysical characterization is needed in order to design and control this process. In the present work we characterize some properties of recently synthetized cationic lipophosphoramidates.

Physicochemical properties of cationic lipophosphoramidates with an arsonium head group and various lipid chains: A structure-activity approach.

We studied the physicochemical properties of some cationic lipophosphoramidates used as gene vectors in an attempt to better understand the link between the nature of the hydrophobic chain and both physico-chemical properties and transfection efficiency. These compounds have an arsonium head group and various chain lengths and unsaturation numbers. The synthesis of cationic phospholipids with oleic (Guenin et al.

Polyethylene glycol aggregates in water formed through hydrophobic helical structures.

The present study was aimed at elucidating the mechanism of aggregation in water of hydroxyl-terminated polyethylene glycol (PEG) of low molecular weight (600 g/mol). The results from fluorescence spectroscopy at different temperatures were consistent with surface tension measurements, suggesting aggregate formation. Indeed, the process of aggregation is accompanied by an increase in the fluorescence emission of a hydrophobic probe.

Direct laser photo-induced fluorescence determination of bisphenol A.

Classical photo-induced fluorescence methods are conducted in two steps: a UV irradiation step in order to form a photo-induced compound followed by its fluorimetric determination. Automated flow injection methods are frequently used for these analyses. In this work, we propose a new method of direct laser photo-induced fluorescence analysis.

Imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry for determination of mercury in seawater.

In this study, direct determination of mercury at the nanogram per liter level in the complex seawater matrix by imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry (ITR-ETA-LEAFS) is described. In the case of mercury, the use of a nonresonant line for fluorescence detection with only one laser excitation is not possible. For measurements at the 253.

Cationic lipo-thiophosphoramidates for gene delivery: synthesis, physico-chemical characterization and gene transfection activity--comparison with lipo-phosphoramidates.

The synthesis of cationic lipo-thiophosphoramidates, a new family of cationic lipids designed for gene delivery, is reported herein. This new class of lipids is less polar than its oxygenated equivalent the lipo-phosphoramidates. Fluorescence anisotropy and FRET were used to determine the fluidity and fusogenicity of the lipo-phosphoramidates 3a-b and lipo-thiophosphoramidates 7a-b.

A study of marine pollution caused by the release of metals into seawater following acid spills.

This study examined the potential metal pollution induced by the accidental spill of different acids into seawater. The acids sink to the bottom according to their densities and subsequently react with marine sediments. The acids selected for this study were acetic, hydrochloric, nitric, sulfuric, and phosphoric acids; the metallic elements selected were Cr, Cu, Fe, Mn, Pb and Zn.

A novel cationic lipophosphoramide with diunsaturated lipid chains: synthesis, physicochemical properties, and transfection activities.

Cationic lipophosphoramidates constitute a class of cationic lipids we have previously reported to be efficient for gene transfection. Here, we synthesized and studied a novel lipophosphoramidate derivative characterized by an arsonium headgroup linked, via a phosphoramidate linker, to an unconventional lipidic moiety consisting of two diunsaturated linoleic chains. Physicochemical studies allowed us to comparatively evaluate the specific fluidity and fusogenicity properties of the liposomes formed.

Spectroscopic properties and laser induced fluorescence determination of some endocrine disrupting compounds.

This work presents spectroscopic properties of some Endocrine Disrupting Compounds (EDCs), frequently found in food and in natural water. Studied molecules belong to the groups of phenolic and phthalate EDCs. In a first part, we have examined their absorption and fluorescence properties.

Fluorescence study of lipid-based DNA carriers properties: influence of cationic lipid chemical structure.

We report here a study on the physicochemical properties of cationic phospholipids liposomes used for lipoplex formulation and DNA transfer. The original cationic phospholipids synthesized in our laboratory are first presented with the liposome formulation process. The second part deals with the liposomes fusogenic properties studied by fluorescence resonant energy transfer (FRET).

Simulations of accidental coal immersion.

Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups--a laboratory seawater canal called "polludrome" is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor.

Lipophosphoramidates as lipidic part of lipospermines for gene delivery.

The DNA compacting properties of polyamines (especially spermine) are well-known, hence the use of spermine as the cationic part in several synthetic DNA carriers. Here, we describe the synthesis of modified spermines, with a "lipophosphoramidate" as the lipidic part, and their use for efficient in vitro transfection. Physicochemical measurements (particle size, zeta potentials, pKa determination) and gel retardation assays were also performed.

Study of trace metal leaching from coals into seawater.

The behaviour of three South African coals in water and, particularly in seawater, was examined. A sequential speciation procedure used to evaluate trace metal partitioning in coal has shown that trace metals will not be easily released from these coals into environmental ecosystems. Only a few trace elements are slightly leached from these coals into water or seawater at pH around 8.

Laser-induced fluorescence detection of carbamates traces in water.

The absorption and fluorescence spectra of carbaryl (CB), carbofuran (CF) and carbendazim (MBC) have been studied. Fluorescence lifetime and fluorescence quantum yields are also reported as well as the influence of pH, solvent and presence of humic acids on fluorescence. The limit of detection (LD) of the three compounds has been measured by direct analysis by laser-induced fluorescence (LIF) using a pulsed YAG laser with an Optical Parametric Oscillator (OPO) as excitation source and an Intensified Charged Coupled Device (ICCD) camera for the fluorescence detection.