A high-temperature superconducting-receiver system for use in nuclear magnetic resonance (NMR) microscopy is described. The scaling behavior of sources of sample and receiver-coil noise is analyzed, and it is demonstrated that Johnson, or thermal, noise in the receiver coil is the factor that limits resolution. The behavior of superconductors in the environment of an NMR experiment is examined, and a prototypical system for imaging biological specimens is discussed. Preliminary spin-echo images are shown, and the ultimate limits of the signal-to-noise ratio of the probe are investigated.
CaF2 films have been grown epitaxially on (100) and (111) Si substrates by molecular beam epitaxy. These films have been characterized by electron microscopy, reflection high-energy electron diffraction, Rutherford backscattering ion channeling, and back-reflection Laue x-ray diffraction. In addition, chemical etching has been used to reveal dislocations and to delineate cracks. Film cracking appears to be related to crystalline perfection through misfit dislocation mobility. It is possible to grow high quality, (xmin=3.0%) single-crystal films on (111) Si which are free of cracks and atomically flat. However, the high free energy of the (100) surface in an ionic fluorite crystal prevents the growth of comparable CaF2 films on the (100) Si surface.
Spinosad is an insect control agent that is derived from a naturally occurring soil bacterium and is effective on several classes of insects, especially Lepidoptera larvae. Spinosad is registered in many countries for use on a variety of crops, including cotton, corn, soybeans, fruits, and vegetables. Residue methods utilizing high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection have been described for determining spinosad and its metabolites in environmental and food matrices. These residue methods typically involve an extraction with organic solvents, followed by purification using liquid-liquid partitioning and/or solid phase extraction prior to measurement by HPLC-UV. The residue methods determine the active ingredients (spinosyns A and D) and up to three minor metabolites (spinosyn B, spinosyn K, and N-demethylspinosyn D). The methods have validated limits of quantitation ranging from 0.010 to 0.040 microgram/g. This paper briefly reviews the residue methodology for spinosad and metabolites in food and environmental matrices and provides a summary of method validation results for 61 different sample types, including newly published results for 37 additional crop matrices and processed commodities.
Spinosad is an insect control agent that is derived from a naturally occurring organism and is effective on a wide variety of crops, including citrus crops. A method is described for the determination of spinosad and its metabolites in citrus crops and orange processed commodities. The method determines residues of the active ingredients (spinosyns A and D) and three minor metabolites (spinosyn B, spinosyn K, and N-demethylspinosyn D). For dried orange pulp and orange oil, the method has a limit of quantitation (LOQ) of 0.02 microg/g and a limit of detection (LOD) of 0.006 microg/g. For all other sample matrices (whole fruit, edible fruit, juice, and peel), the method has an LOQ of 0.01 microg/g and an LOD of 0.003 microg/g. The analytes are extracted from the various sample types using appropriate solvents, and the extracts are purified by liquid-liquid partitioning and/or solid-phase extraction. All five analytes are determined simultaneously in the purified extracts by reversed-phase high-performance liquid chromatography with ultraviolet detection at 250 nm.
Spinosad is a naturally derived insect-control agent for use on cotton and a variety of other crops.
A method is described for the determination of spinosad and its major metabolites in beef and poultry
meat, milk, cream, and eggs. The method determines residues of the active ingredients (spinosyns
A and D) and two metabolites (spinosyn B and N-demethylspinosyn D). For chicken fat, the method
has a limit of quantitation (LOQ) of 0.02 μg/g and a limit of detection (LOD) of 0.006 μg/g. For all
other chicken tissues, beef tissues, milk, cream, and eggs, the method has an LOQ of 0.01 μg/g and
an LOD of 0.003 μg/g. The analytes are extracted from the various sample types using appropriate
solvents, and the extracts are purified by liquid−liquid partitioning and solid-phase extraction. All
four analytes are determined simultaneously in the purified extracts by reversed-phase high-performance liquid chromatography with ultraviolet detection at 250 nm.
Keywords: Spinosad; spinosyn A; spinosyn D; spinosyn B; N-demethylspinosyn D; beef; poultry;
chicken; meat; milk, cream; eggs; quantitation; HPLC-UV
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