A quenching fluoroimmunoassay for analysis of the pesticide propazine in an apolar organic solvent, reverse micelles of AOT inn-octane: Effect of the micellar matrix and labeled antigen structure

A simple way of directly observing antigen-antibody binding in a reverse micellar system,n-octane containing reverse micelles of aerosol OT (AOT), using the hydrophobic pesticide propazine as antigen, is described. We observed two processes during fluorescein-labeled propazine (FP)-antibody (Ab) interaction in reverse micelles: (1) quenching of the fluorescence of FP after mixing of Ab and FP (due immune complex formation) and (2) restoration of FP fluorescence after addition of excess propazine to the immune complex formed. We found that the quenching efficiency depends on both the properties of the reverse micellar system (surfactant concentration, hydration degreeW ₀ = [water]/[surfactant]) and the structure of the labeled antigen. A quenching fluoroimmunoassay of propazine both in apolar organic solvents and in water is developed. The method is homogeneous. The quenching time is 10–30 min, and the detection limit of propazine is 100 nM (20 Μg/L) in organic solvent and 10nM (2 Μg/L) in water. Propazine can be added to the reverse micellar system when dissolved in AOT/octane, or in an octane/chloroform mixture, or in chloroform. This makes possible the use of the analysis directly for pesticide extracts in nonpolar organic solvents.     

Preparative Procedure for the Reduction of Substituted Nitroarenes with Hydrazine Hydrate in the Presence of a Nickel–Cobalt Nanocatalyst

A preparative procedure has been proposed for the reduction of substituted nitroarenes with hydrazine hydrate in the presence of a nanocatalyst based on cobalt–nickel nanoparticles, which ensured selective formation of the corresponding anilines in 78–80% yield in 20–45 min.     

Photochemical-fluorimetric method for the determination of total chlorophenoxyacid herbicides

A room temperature photochemically-induced fluorescence (RTPF) method is proposed for the quantitative analysis of seven widely-used chlorophenoxyacid herbicides. The influence of organic solvent, pH (in aqueous solutions), methanol percentage, and UV irradiation time on the excitation and emission wavelengths and fluorescence intensity was investigated. It was found that the largest fluorescence signals were obtained in a mixture of methanol and pH 5 buffer (50/50, v/v), while organic solvents and water produced generally lower signals. The tri- and bichlorinated phenoxyacid herbicides were photolysed significantly more slowly than the monochlorinated derivatives, and the derivatives of 2-propionic acid were photodegraded more quickly than the corresponding derivatives of acetic and butyric acid. Selected UV irradiation times were found to be 15 min for all herbicides under study. Linear calibration graphs were established over about one to two orders of magnitude in the interval 0.1-10 mug ml(-1). The RTPF limits of detection were between 36 ng ml(-1) and 179 ng ml(-1), according to the compound. Analytical application of RTPF to river water samples containing chlorophenoxyacid herbicides is discussed.     

Reactions of trans-[OsO2Cl2L2] (L = PPh3, AsPh3, SbPh3) with Acetic Acid

The possibility of reactions between trans-[OsO₂Cl₂L₂] (L = PPh₃, AsPh₃, SbPh₃) osmium(VI) complexes and glacial acetic acid to give osmium(IV) compounds of general formula [Os₂(-O)(-O₂CCH₃)₂Cl₄(L)₂] was studied.     

Using fast digital converters to detect bremsstrahlung radiation during the alpha decay of heavy nuclei

A large-volume germanium detector coupled with fast signal digitizers is proposed for use in experiments to study interference effects in yields of the bremsstrahlung radiation that accompanies alpha decays of heavy nuclei. When wavelet processing is applied to the signals from detectors, the time resolution can be as fine as ~30 ns for a detector with a volume of ≥100 cm³. This method is used to measure experimentally the probability of the emission of γ-quanta from excited states of daughter nuclei produced in the α-decay chain of ²²⁶Ra.     

Preparation of lead sulfide nanoparticles in the photolysis of aqueous solutions of lead thiosulfate complex

It was found from spectroscopic and microscopic data that lead sulfide nanoparticles are formed during the UV irradiation of aqueous solutions of lead thiosulfate complex. The yield and the size of the lead sulfide nanoparticles depend on the concentration of solution and the lead to thiosulfate ion ratio in the solution.     

A Fluorescence Polarization Immunoassay Procedure for Determining Dibutyl Phthalate in Water

Journal of Analytical Chemistry - We developed a fluorescence polarization immunoassay (FPIA) procedure for determining the dibutyl phthalate (DBP) plasticizer, a toxic technogenic environmental...     

Analytical Representation of the Integral Scattering Cross-Section in the Integrofunctional Discrete Source Method

Differential Equations - An analytical expression is obtained for the total scattering cross-section in the discrete source method, which uses the representation of the far field pattern of the...     

Prefracture time of gabbro specimens in a damage accumulation model

In the work, we experimentally determined the characteristic prefracture time of gabbro specimens in three-point bending. The obtained prefracture time was used to estimate the parameters in a model of brittle and quasibrittle material. Based on the verified model, numerical modeling was performed to describe the stress-strain evolution in gabbro specimens under three-point bending. The experiment and numerical calculations show that the final deformation stage involves beam deflection in blowup mode.