A collaborative study was conducted to validate a method for the determination of glyphosate and aminomethylphosphonic acid (AMPA) in crops. The analytes are extracted from crops with water, and the crude extracts are then subjected to a cation exchange cleanup. The analytes are derivatized by the direct addition of the aqueous extract into a mixture of heptafluorobutanol and trifluoroacetic anhydride. The derivatized analytes are quantitated by capillary gas chromatography with mass-selective detection (MSD). The collaborative study involved 13 laboratories located in 5 countries 12 laboratories returned valid data sets. The crops tested were field corn grain, soya forage, and walnut nutmeat at concentrations of 0.050, 0.40, and 2.0 mg/kg. The study used a split-level pair replication scheme with blindly coded laboratory samples. Twelve materials were analyzed, including 1 control and 3 split-level pairs for each matrix, 1 pair at each nominal concentration. For glyphosate, the mean recovery was 91%, the average intralaboratory variance, the repeatability relative standard deviation (RSDr), was 11%, and the interlaboratory variance, the reproducibility relative standard deviation (RSDR), was 16%. For AMPA, the mean recovery was 87%, the RSDr was 16%, and the RSDR was 25% at mg/kg levels.

The inhibition of the thermal reaction between hydrogen and oxygen by hydrogen bromide lias bccn studied over a wide range of mixture composition and vessel diameter at 50072 using vessels coated with boric acid. Under these conditions, surface reactions arc unimportant and the inhibition arises through the sequence of reactions : H+HBr = H24-Br

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A Langmuir probe technique has been used to measure electron energy distribution functions in the positive column of a D C glow discharge in oxygen. The electron energy distribution function is shown to fit a functional form given by f(E) = CE1I2 exp (-BEn) where n = 1.6 + 0 . 1 ; the average electron energies lie between 4.4 and 5.0 eV.Une sonde de Langmuir a Cte utiliste pour mesurer les fonctions de distribution d'Cnergie des Clectrons dans la colonne positive d'une decharge luminescente a courant continu dans I'oxygene. On montre que la fonction de distribution d'energie des Clectrons est decrite par la forrne analytique f(E) = CE112 exp (-BE3 oh n = 1.6 + 0.1 ; les energies moyennes des Clectrons se situent entre 4.4 et 5.0 eV. [Traduit par le journal]Can.

On treatment with dodecylammonium chloride, a synthetic Na-saturated phyllomanganate undergoes a cation-exchange reaction in which the structure expands from a collapsed basal spacing of 7 ,~ or a hydrated one of 10 N to ~ 25-5 •. The exchange reaction is strongly influenced by the saturating cation in the original manganate and by the degree of hydration of the interlayer zone in which the exchangeable cations are located. Of the 12 cations tested, from Groups IA, IIA and lIB of the Periodic Table, only Co-manganate undergoes alkylammonium exchange when fully-dehydrated by evacuation. The results are discussed in the context of existing knowledge of the synthetic phyllomanganate and, by extrapolation, the potential value of the technique in the characterization of natural manganates has been assessed.