Development of a new automatic on-site detector of pesticides in natural waters by photo induced fluorescence, application to three phenylurea and benzoylurea herbicide.

Prototypes of on-site automatic photo induced fluorescence detectors of pesticide in natural waters are set up and applied for the determination of the benzoyl- and phenylurea pesticides, namely fluometuron, monolinuron and diflubenzuron. As these pesticides present no native fluorescence the set up system use the photo conversion under UV irradiation of these pesticides into highly fluorescent photoproducts. A first system, called AUTOPIF, (evolution the commercial AQUAPOD system) is develop using a detection via a diode array spectrometer. To improve the sensitivity of the method, a second system, called AUTOPIF+, is developed with a more resolute spectrometer and an intensified CCD camera detection. Analytical applications were carried out in aqueous solution and detected on line with the AUTOPIF and AUTOPIF+ system. The calibration curves are linear over one order of magnitude, and the limits of detection are in the µg mL-1 range. The analytical performances of these methods for the determination of the three pesticides are satisfactory in comparison to other classical PIF methods published for the determination of phenylurea pesticides in aqueous solutions. Our results show that the AUTOPIF and AUTOPIF+ methods are versatile, sensible and can be easily applied as an alert system to detect pollutant residues in naturals waters over a threshold value.

A new direct laser photo-induced fluorescence method coupled on-line with liquid chromatographic separation for the simultaneous determination of anilides pesticides.

A new direct laser photo-induced fluorescence high performance liquid chromatography (DL-PIF-HPLC) method is developed for the simultaneous determination of three anilide pesticides, namely carboxin, monalide and propanil. DL-PIF-HPLC uses a tunable Nd:YAG-OPO laser to obtain fluorescent photoproduct(s) and to simultaneously analyze their fluorescence in a short acquisition time with an intensified CCD camera, which improves the selectivity (by choosing the suitable excitation wavelength), increases the sensitivity (due to the high energy of the laser beam) and reduces the time of analysis, relative to the classical PIF methods. However, one of the main drawbacks of PIF methods is the presence of interferences with other compounds, such as other pesticides from the same group yielding similar fluorescent photoproducts, which reduces their selectivity. The analytical interest of DL-PIF-HPLC to avoid these interferences is demonstrated. The DL-PIF spectra, chromatographic conditions and analytical performances of DL-PIF-HPLC are presented for the simultaneous determination of three anilide pesticides. The calibration curves are linear over one order of magnitude and the limits of detection are in the ng mL(-1) range. The new DL-PIF-HPLC system has the advantage to combine the performances of both techniques, DL-PIF and liquid chromatography, and to improve the analysis selectivity.

Photochemically-induced fluorescence properties of two benzoyl- and phenylurea pesticides and determination in natural waters.

A photo-induced fluorescence (PIF) method was developed for the determination of two benzoyl- and phenylurea pesticides, namely diflubenzuron (DFB) and fenuron (FEN). The photoconversion under UV irradiation of both pesticides into strongly fluorescent photoproducts was performed in several media (methanol, ethanol, acetonitrile, pH4 aqueous solution and pH4 water-methanol (30:70, v/v) mixture). PIF parameters were optimized. Analytical figures of merit for the PIF determination of DFB and FEN were satisfactory, with rather wide linear dynamic range (LDR) values of one to two orders of magnitude, relatively low limit of detection (LOD) values of, respectively, 9-24 ng/mL for DFB and 1-28 ng/mL for FEN, and limit of quantification (LOQ) values of, respectively, 30-80 ng/mL for DFB and 4-95 ng/mL for FEN, according to the medium. Relative standard deviation (RSD) values were in the range 1.7-5.6%. PIF was validated by comparing its analytical performances to those of a standard UV absorption spectrophotometric method. The optimized PIF method was applied to the quantitative analysis of both pesticides in various spiked natural water samples collected in a Senegal agricultural area by the standard addition procedure prior to extraction steps in dichloromethane, with satisfactory mean recovery percentage values (97.0-105.3 for DFB and 98.3-102.8% for FEN). An interference study of foreign species, including pesticides and inorganic ions, likely to be present in natural waters, was also carried out.

Determination of phenylurea pesticides by direct laser photo-induced fluorescence.

A direct Laser Photo-Induced Fluorescence (DL-PIF) method is developed for the determination of two phenylurea pesticides, namely fenuron and diflubenzuron. The DL-PIF method uses a tunable Nd:YAG-OPO Laser to obtain the photoproduct(s) and to simultaneously analyse their fluorescence in a short acquisition time on an intensified CCD camera. Compared to classical PIF methods, the use of a tunable laser improves the selectivity (by choosing the suitable excitation wavelength), increases the sensitivity (due to the high energy of the beam) and also reduces the time of analysis. The analytical performances of this method for the determination of both pesticides are satisfactory in comparison to other classical PIF methods published for the determination of phenylurea pesticides. The calibration curves were linear over one order of magnitude and the limits of detection were in the ng mL(-1) range. Satisfactory recoveries were obtained in the analysis of both pesticides in river and sea water spiked samples.

Application of flow injection analysis--photo-induced fluorescence (FIA-PIF) for the determination of α-cypermethrin pesticide residues in natural waters.

Flow injection analysis combined with photo-induced fluorescence (FIA-PIF) has been applied for the determination of α-cypermethrin pesticide residues in Senegalese natural waters, using organic solutions and cyclodextrin (ß-cyclodextrin and 2-hydroxypropyl-ß-cyclodextrin) aqueous media. The α-cypermethrin insecticide has a very weak natural fluorescence, but it is converted into strongly fluorescent photoproduct(s) by UV irradiation. Cyclodextrins were found to enhance the PIF signal. FIA parameters, including mobile phase flow rate, injected volume, and reactor length, were optimized. Analytical performances of the FIA-PIF method for the determination of α-cypermethrin were satisfactory, with concentration linear dynamic ranges over one to two orders of magnitude and with rather low limits of detection and limits of quantification, in the ng mL(-1) range, and relative standard deviations comprised between 1.2% and 3.8%. Application of FIA-PIF for the analysis of fortified natural water samples collected from Senegal yielded good recovery values (84-112%). Because of its high sampling rate, the FIA-PIF method constitutes a rapid analytical tool, useful for quantification of α-cypermethrin residues in natural waters.

Toxicological study of pesticides in air and precipitations of Paris by means of a bioluminescence method.

A detailed toxicological study on several pesticides, including chlorothalonil, cyprodynil, dichlobénil, pendimethaline, trifluraline, and alpha-endosulfan, present at trace levels in air and total atmospheric precipitations of Paris is presented. The pesticides contained in the atmospheric samples, collected during sampling campaigns in February-March 2007, are identified and quantified by a high-performance liquid chromatographic (HPLC)-UV detection method. The toxicity measurements are performed by means of the Microtox bioluminescence method, based on the evaluation of the bioluminescence inhibition of the Vibrio fischeri marine bacteria at two exposure times to the pesticide solutions. The specific toxicity, corresponding to the particular toxicity of the compound under study and represented by the EC(50) parameter, is determined for these pesticides. Also, the global toxicity, which is the toxicity of all micro-pollutants present in the sample under study, is estimated for the extracts of air and atmospheric precipitation (rainwater) samples. The specific toxicities strongly vary with the nature of the pesticide, the EC(50) parameter values being comprised between 0.17 and 0.83 mg/mL and 0.15 and 0.66 mg/mL, respectively, for exposure times of 5 and 15 min. The importance of the atmospheric samples' global toxicity and the respective contribution of the toxic potency of the various pesticides contained in these samples are discussed.