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.

Backscattered speckle size as a function of polarization: influence of particle-size and- concentration.

This report about backscattering measure-ments of the speckle produced by strongly-scattering liquid media shows that the size of the backscattered speckle depends on scattering and anisotropy coefficients. These measurements were aimed at assessing the effects of polarization characteristics of the incident laser beam and of the scattered light on speckle size. The samples under study consisted of monodisperse polystyrene microspheres in solutions, mixtures of different sized-microspheres, milk, blood and pig skin. Such measurements of speckle size in polarization give information on strongly scattering media, allow their discrimination and enable one to characterize the undergone changes.

Scattering through fluids: speckle size measurement and Monte Carlo simulations close to and into the multiple scattering.

We report on measurements in transmission of the speckle produced by scattering liquid media: diluted milk and water solutio ns of polystyrene-microspheres of different diameters. The speckle size is affected not only by scattering parameters such as the optical thickness, but also by the dimensions of the scatters. From the speckle measurement, we propose a method to differentiate media. Moreover, a calculation of the transmitted light profile by Monte Carlo simulation allowed us to get a better insight on the speckle size evolution versus scattering.

Polarization errors associated with zero-order achromatic quarter-wave plates in the whole visible spectral range.

By a combination of quarter-wave plates made of different birefringent materials it is possible to produce achromatic quarter-wave plates whose degree of achromatism is dependant on the dispersions of birefringence and on the thicknesses of the individual quarter-wave plates. These waveplates are widely used in optical instrumentation and the residual errors associated with these devices can be very important in high resolution spectro-polarimetry measurements. The misalignment of optic axis in a double crystal waveplate is one of the main source of error and leads to elliptical eigenpolarization modes in the retarder and the oscillation of its orientation according to the wavelength. This paper will discuss, first, how the characteristics of a quartz-MgF2 quarter-wave plate is affected by such a misalignment. A correlation with the experiment is then achieved in order to highlight the interest of taking a possible tilt error into consideration when doing polarimetric measurements.

The prevalence of exfoliation syndrome in different areas of France.

A prospective study was performed by 30 ophthalmologists to determine the prevalence of exfoliation syndrome (ES) in different areas of France and its relationship with glaucoma. The prevalence of ES in France is 5.5%; there are geographical variations: in Brittany and in the South East, the prevalence of ES is statistically higher than in the other areas. The percentage of patients with ES and glaucoma is 65.5%. The mean age of patients with ES with glaucoma (74.8) is significantly lower than the mean age of patients with ES without glaucoma (76.9). The association of ES with glaucoma appears early and does not increase with age.

A comparison of native and covalently crosslinked creatine kinases: denaturation and reassembly.

Creatine kinase from rabbit muscle, a dimeric protein of molecular weight 81,000, was crosslinked with glutaraldehyde. The time course of the reaction was monitored by inhibition of activity, fluorescence polarization, and electrophoretic mobility in polyacrylamide slab gels containing sodium dodecyl sulfate. Inactivation is complete in 40 min. ADP (1.2 mM) decreases the rate but does not prevent complete inactivation. Fluorescence polarization analysis of N-dansylaziridyl creatine kinase suggests the formation of high molecular weight oligomers. This is confirmed through electrophoretic molecular weight analysis, which demonstrates the formation of products with molecular weight greater than 150,000 throughout the course of reaction with glutaraldehyde. During crosslinking at least three other products appear with apparent molecular weights of 150,000, 95,000, and 85,000. The 150,000 and 95,000 molecular weight products are transient, disappearing after 40 min of exposure to glutaraldehyde. Monomers of 40,000 molecular weight have also been eliminated by 40 min. The 85,000 molecular weight product, which is not present until 10 min after crosslinking, is the only product other than oligomers present at 60 min of crosslinking. These two products are separated by gel filtration. The isolated 85,000 molecular weight protein exhibits absorption and fluorescence spectra identical to those of noncrosslinked creatine kinase. Upon denaturation in 8 M urea, the noncrosslinked and crosslinked preparations undergo a 2.8-fold and 2.0-fold increase, respectively, in intrinsic protein fluorescence. Since crosslinked enzyme is incapable of dissociation upon denaturation, the difference in fluorescence (28%) between crosslinked and noncrosslinked protein in denaturant may be attributed to the contribution of dissociation to the total fluorescence change resulting from denaturation. The kinetics of reassembly of both preparations exhibit a rapid, initial decrease in fluorescence, followed by a slower, more protracted decline until the level of fluorescence of the undenatured proteins is achieved. The decrease in fluorescence during the first phase of reassembly is 93 and 72% of the total fluorescence change for crosslinked and noncrosslinked enzyme, respectively. Since, the magnitude of these changes is considerably greater than the fluorescence change attributed to association of subunits, the first kinetic phase cannot reflect dimerization, and most probably constitutes the refolding of subunits. The second, slower phase of reassembly, which is approximately 28% of the fluorescence change observed in the reassembly of noncrosslinked enzyme, but only 7% for crosslinked species, may be assigned to reassociation.