A procedure is reported for the selective ammonia chemical ionization of some nitrogen and sulfur heterocycles in petroleum fractions using ion trap mass spectrometry (ITMS). The ion trap scan routine is designed to optimize the population of ammonium reagent ions and eject from the trap (by radio frequency/direct current isolation) electron ionization products formed during reagent ion formation prior to ionization of the sample. The ITMS procedure is compared with standard ion trap detector and conventional quadrupole ammonia chemical ionization for the determination of nitrogen and sulfur heterocycles in gas oil and kerosine samples. Greatly enhanced selectivity is shown for the ITMS procedure by suppression of competing charge-exchange processes.
The potential use of polyurea microcapsules, as Ôrelease carriersÕ for insect pheromones, has been demonstrated. (Z)-11-hexadecenyl acetate (Z11-16:Ac), the major sex pheromone component of several Noctuidae species, was used as the model molecule. The coating material's ability to release the pheromone was initially studied by the solid-phase micro-extraction technique. Polyurea microcapsules released Z11-16:Ac relatively slowly, with a duration of approximately 1 month, as it was determined under both laboratory and semi-field conditions. Preliminary laboratory bioassays revealed a satisfactory attraction of Sesamia males, at doses of 50 and 500 mg of dried microcapsules containing the aforementioned pheromone. Almost all male insects tested initiated flight and among them 40.2-49.4% successfully contacted the pheromone source. The preparation of polyurea microcapsules needs further refinement as to increase release duration; nevertheless, these results demonstrate strong potential for the future use of polyurea microcapsules as part of integrated insect control programmes.
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