Determination of 22 triazole compounds including parent fungicides and metabolites in apples, peaches, flour, and water by liquid chromatography/tandem mass spectrometry

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed for the determination of 14 parent triazole fungicides and 8 of their metabolites found in apples, peaches, flour, raw water, and tap water. The triazole fungicides chosen for this multiresidue method development project included propiconazole, fenbuconazole and its RH-9129 and RH-9130 metabolites, cyproconazole, difenoconazole, tebuconazole and its HWG 2061 metabolite, hexaconazole, bromuconazole (both stereoisomers), epoxiconazole, tetraconazole, triticonazole and its RPA-404886 and RPA-406341 metabolites, triadimefon, triadimenol, and myclobutanil. Of special concern to the U.S. Environmental Protection Agency were the metabolites common to all triazole fungicides: free triazole, 1,2,4-triazole (T), and its 2 conjugates: triazolylalanine (TA) and triazolylacetic acid (TAA). These metabolites were the primary focus of this project. All samples we cleaned up by a combination of C18 solid-phase extraction (SPE), mixed-mode cationic SPE, and mixed-mode anionic SPE columns. A triple-stage quadrupole mass spectrometer, equipped with electrospray ionization in the positive-ion mode, was used to determine the compounds of interest. T, TA, and TAA were quantitated using isotopically labeled internal standards (IS), in which the 1,2,4-triazole ring had been synthesized by using 13C and 15N (IS_T, IS_TA, and IS_TAA). These isotopically labeled internal standards were necessary to correct for matrix effects. The T, TA, and TAA metabolites were quantitated at the 25-50 parts-per-billion (ppb) level in food commodities and at 0.50 ppb in water. Recoveries were 70-101% from apples, 60-121% from peaches, 57-118% from flour, 75-99% from raw water, and 79-99% from tap water.     

High-resolution solid-state 19F-NMR spectroscopy of the sorption and diffusion of fluorine-containing aromatic molecules in polymeric media

High-resolution ¹⁹F solid-state NMR spectroscopy was employed to study the sorption properties of hexafluorobenzene (HFB) and 3,5-bis (trifluoromethyl) aniline (TFMA) in polystyrene (PS) and butyl rubber (BR). The NMR spectra indicate that the penetrants undergo dual-mode sorption in the glassy polymer (PS), but are highly mobile in the rubbery polymer (BR). In addition, the NMR method was utilized in the experimental determination of diffusion coefficients for the HFB/PS, TFMA/PS, and HFB/BR systems through desorption studies. The diffusion results for the TFMA/PS case agree very well with those previously obtained via resonance nuclear reaction analysis. © 1993 John Wiley & Sons, Inc.     

Generation and assembly of spheroid-like particles

This paper reports a straightforward approach in generating spheroid-like particles and also the orientational orders observed in the self-assembly of these particles. Nonspherical particles, such as spheroid-like particles, are useful in both fundamental studies and industrial applications due to the geometry impact that they bring to the bulk properties of various material systems. Developing processes to generate nonspherical particles is an ongoing quest to meet the need of using such particles in different applications. The approach reported here takes advantage of a controlled chemical etching process. Exposing the spherical silica particles partially to carbon tetrafluoride in a reactive ion plasma-etching chamber transformed the particles from spherical shape into spheroid-like shape. A simple model is proposed to predict the geometry of the resulting nonspherical particles. The shape and dimension of the nonspherical particles generated through such a process matched well with the prediction of the model. The assembly of these spheroid-like particles showed a unique orientational order associated with the alignment of their axes. This approach will help further studies on the fundamental properties of the nonspherical particles, such as packing, rheology, and optical interaction.