Multi-residue method for rapid screening and confirmation of pesticides in crude extracts of fruits and vegetables using isocratic liquid chromatography with electrospray tandem mass spectrometry

A LC-MS-MS method capable of the quantitative determination of a range of pesticide residues present in crude extracts from a variety of fruit and vegetables has been developed. Isocratic LC conditions have been used in conjunction with electrospray ionisation tandem mass spectrometry to detect and identify up to 38 pesticides presented as various mixtures in different matrices. The utility of the method is demonstrated by the analysis of crude extracts, with no sample clean up, from grape, kiwi fruit, strawberry, spinach, lemon, peach and nectarine. Mean recoveries ranging from 63 to 96% with relative standard deviations < 20% were obtained for 30 of the 38 pesticides following analysis of organic produce fortified at concentrations between 0.01 and 0.8 mg/kg. Detected residues were quantified from interpolation against calibration data generated using matrix-matched standards that covered analyte concentration ranges between 0.005 and 0.8 microg/ml. Conditions suitable for the qualitative and quantitative confirmation of residues detected in samples are specified.     

Synthesis of new fluorescent dyes in the benzoxazinone series: Aminobenzoxazinones with a rigidized structure

The structure of 7-aminobenzoxazinones was modified by enclosing their amino nitrogen atom in a julolidyl ring. This rigidization was expected to enhance the fluorescence performances in this series. Several fluorescent dyes and styryl derivatives were prepared and their spectral characteristics were investigated. Comparison with homologous benzoxazinones with a flexible amino group shows that rigidization does not improve the quantum yield and the photochemical stability, in contrast with the results reported for other classes of dyes, like coumarins or rhodamines.     

Planar defects in β-alumina

Sodium β-alumina crystals were elaborated by melting of a mixture of Na₂CO₃ and Al₂O₃ or by PbO flux evaporation and were studied by transmission electron microscopy. They exhibit regular planar defects lying in the {11.0} prismatic planes. These defects are described as antiphase boundaries for the cationic sublattice with fault vectors $\text{1}\text{2}\text{〈10.0〉}$ (such faults do not affect the anionic sublattice). As a consequence it would be interesting to study precisely the structure of the sodium β cationic lattice in the vicinity of the melting point.     

Effect of diffusion on rates and molecular weights in graft polymerization

A theoretical analysis has been made of the graft polymerization process in terms of the quantitative interrelationship between the initiation rate R_i, the k_p/k_t^1/ ratio of the monomer, the equilibrium solubility M of the monomer in the polymer, the polymer film thickness L, and the diffusivity D of the monomer in the polymer. It is shown how the values of these parameters in any grafting system interact to lead to diffusion-controlled graft polymerization. Whether graft polymerization is diffusion-free or diffusion-controlled depends on the values of K_p, d, k_p/k_p^1/2, and L as gathered in the parameter A = [(K_p/k_t^1/2)R_i, D,/^1/2] L/2. When the values of the various terms are such that A is less than 0.1 (i.e., D is large while R_i, k_p, and L are small), the reaction is diffusion-free. When A is greater than 3 (i.e., D is small while R_i, k_p, and L are large), the reaction is diffusion-controlled. The derived equations showing the relationship between kinetic and diffusional parameters are theoretically applicable to all grafting systems, i.e., for all monomer-polymer combinations under all conditions of reaction temperature, radiation intensity and polymer film thickness. The theoretical analysis has been verified for the rate and degree of polymerization for the radiation-induced graft polymerization of styrene to polyethylene.     

Action des perfluoroalkylcuivre(I) sur les perfluoroalkylethylenes

A series of new polyfluorinated dienes 3, containing the novel -CFCHCHCF-, pattern has been synthesized (50–70% yields) by reacting perfluoroalkyl iodides with perfluoroalkyl-ethylenes in the presence of copper. The monoalkenes R_fCFCHCH₂CF₂R′_f and the saturated compounds R_fCF₂CH₂CH₂CF₂R′_f were obtained by varying the experimental conditions. The ¹H and ¹⁹F NMR spectra are analysed and the reaction mechanism is discussed.     

The preparation of precisely defined lithium isotope mixtures

The need for accurate (< 0.06%) isotopic blends of ⁶Liand ⁷Li is explained and their preparation is discussed. It is shown that lithium must be determined at an accuracy level better than 0.035%. Four methods — acid-base titration with hydrochloric acid or benzoic acid, and weighing as sulphate or carbonate — were tested and improved for the precise and accurate analysis of lithium hydroxide solutions. The results of these four methods for a 0.1 M solution agreed within ± 0.02%. The preparation of pure isotopically enriched lithium hydroxide solutions, with specially purified cation- and anion-exchangers, is described. The prepared products contain as little as 100 μg of other alkali metals and 50 μg of alkaline-earth metals per gram of lithium, and are sufficiently free of anions to permit accurate chemical assay of lithium. No changes in the isotopic compositions of 99% ⁶Li or 99.99% ⁷Li were detected during the treatment.     

Conversion of 3-benzoyl-1-methyl-4-phenyl-γ-piperidol by arylamines and arylhydrazines. Synthesis of 3-arylamino-1-oxo-1-phenylpropanes and 1,3-diarylpyrazoles and their fragmentation under electron impact

It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007.     

Reduction par les sels chromeux de bromures benzyliques ortho-o-acyles avec transposition du groupement acyle : De l'' ester : acces aux ortho-hydroxybenzyl cetones non masquees et une nouvelle preparation de benzo¦b¦furannes substitues en position-2

The σ-bonded organochromium (III) complexes resulting from the reduction of -O-acyl benzylic bromides with CrCl₂., undergo an 1,5-transposition of the ester acyl functional group which allows, through selected experimental conditions either a selective access to the unmasked -hydroxybenl ketones or a new preparation of the 2-substituted benzo¦b¦furans . The scope and limitations of the method are presented.     

Wafer and epilayer improvement for integrated optics devices on InP: the ESPRIT project 2518

Ga _x In_1–x As _y P_1–y alloys lattice matched to InP substrates are currently used to fabricate optoelectronic and integrated optics devices. To achieve devices with high performances and high fabrication yield, the uniformity and reproducibility of the Ga _x In_1–x As _y P_1–y epitaxial layers (composition, thickness, doping, etc.) have become key parameters. These problems have been addressed in the frame of ESPRIT project 2518 and are presented in this paper. Several aspects have been considered starting from the optimization of InP substrates, the MOVPE growth of uniform GalnAsP layers, the material characterization to the validation of material uniformity on passive optical waveguides. Both scanning photoluminescence analysis and waveguide losses measurements performed on 2 inch wafers with a high lateral resolution have shown that high quality uniform GalnAsP layers can be obtained reproducibly on 2 InP substrates using a commercially available LP-MOCVD growth process. In particular, more than 60% of 36 mm long, 3m wide and 100m spaced rib waveguides exhibit losses below 0.8dBcm^–1.