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41.
The accuracy, repeatability, and reproducibility characteristics of a method using multitoxin immunoaffinity column cleanup with liquid chromatography (LC) for determination of aflatoxins (AF; sum of aflatoxins B1, B2, G1, and G2) and ochratoxin A (OTA) in powdered ginseng and ginger have been established in a collaborative study involving 13 laboratories from 7 countries. Blind duplicate samples of blank, spiked (AF and OTA added) at levels ranging from 0.25 to 16.0 microg/kg for AF and 0.25 to 8.0 microg/kg for OTA were analyzed. A naturally contaminated powdered ginger sample was also included. Test samples were extracted with methanol and 0.5% aqueous sodium hydrogen carbonate solution (700 + 300, v/v). The extract was centrifuged, diluted with phosphate buffer (PB), filtered, and applied to an immunoaffinity column containing antibodies specific for AF and OTA. After washing the column with water, the toxins were eluted from the column with methanol, and quantified by high-performance LC with fluorescence detection. Average recoveries of AF from ginseng and ginger ranged from 70 to 87% (at spiking levels ranging from 2 to 16 microg/kg), and of OTA, from 86 to 113% (at spiking levels ranging from 1 to 8 microg/kg). Relative standard deviations for within-laboratory repeatability (RSDr) ranged from 2.6 to 8.3% for AF, and from 2.5 to 10.7% for OTA. Relative standard deviations for between-laboratory reproducibility (RSDR) ranged from 5.7 to 28.6% for AF, and from 5.5 to 10.7% for OTA. HorRat values were < or = 2 for the multi-analytes in the 2 matrixes.  相似文献   
42.
Methodology and Computing in Applied Probability - In this paper we study approximations for the boundary crossing probabilities of moving sums of i.i.d. normal random variables. We approximate a...  相似文献   
43.
Mesoporous hollow carbon nanospheres (MHCS) have been extensively studied owning to their unique structural features and diverse potential applications. A surfactant‐free self‐assembly approach between resorcinol/formaldehyde and silicon alkoxide has emerged as an important strategy to prepare MHCS. Extending such a strategy to other substituted phenols to produce heterogeneous‐atom‐doped MHCS remains a challenge due to the very different polymerization kinetics of various resins. Herein, we report an ethylenediamine‐assisted strategy to control the cooperative self‐assembly between a 3‐aminophenol/formaldehyde resin and silica templates. Nitrogen‐doped mesoporous invaginated carbon nanospheres (N‐MICS) with an N content of 6.18 at %, high specific surface areas (up to 1118 m2 g?1), large pore volumes (2.47 cm3 g?1), and tunable mesopores (3.7–11.1 nm) have been prepared. When used as electrical double‐layer supercapacitors, N‐MICS show a high capacitance of 261 F g?1, an outstanding cycling stability (≈94 % capacitance retention after 10 000 cycles), and a good rate performance.  相似文献   
44.
The addition polymerization of a ferrocenyl-substituted P[double bond]C bond leads to new redox-active polymers with functional ferrocene and phosphine moieties.  相似文献   
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Theoretical evidence for the validity of the formulaE =mc 2 for gravitational energy in general relativity is reviewed. For isolated bodies the formula applies to both the inertial mass and the mass as a source of gravity. The formula also holds for the case of the mass density (as a source of gravity) of an inhomogeneous medium with small-scale gravitational interactions.  相似文献   
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Gas chromatography (GC) has been interfaced very simply and inexpensively with a flame photometric detector (FPD) and a direct current plasma (DCP) atomic emission spectrometer in order to perform highly specific and selective determination of organotins in fish and shellfish samples. GC–FPD studies employed a fused-silica, megabore column with a thin, immobilized stationary phase of DB-17 (1 μm thickness), with a commercially available GC–FPD instrument. No prior alkylation or hydridization reactions were performed on the organotins; rather they were separated as the original, native species. Separate GC–FPD and GC–DCP injections and quantitative determinations have been performed, though simultaneous FPD/DCP detection on a single injection is suggested. This permitted routine qualitative and quantitative determinations of organotin species in complex food matrices (fish/shellfish) via both element selective detectors. Isothermal GC–FPD/DCP conditions permitted baseline resolution of all four tin species of interest today: monobutyl-, dibutyl-, tributyl- (TBT), and tetrabutyl-tin. Optimization of the GC–DCP interface was accomplished, followed by a determination of detection limits and linearity of the calibration plots, and a comparison of the results with those obtained by the newer GC–FPD approach (which was also developed here). In three sample instances, qualitative and quantitative results for naturally occurring and spiked levels agreed for both the GC–FPD and GC–DCP approaches. Improved sample preparation and extraction procedures have been developed for organotins from fish samples involving extraction with an organic solvent, concentration, saponification, back-extraction, and injection of the eluent onto the GC column. Quantitative levels of organotins (solely TBT) in fish and shellfish are reported for samples from Europe, Korea, Scandinavia, and the USA.  相似文献   
50.
The macroscopic stress-energy tensor of an astronomical medium such as a galaxy of stars is determined by the field equation of general relativity from the small-scale variations in mass and velocity. In the weak-field, slow-motion approximation, in which the gravitational fields of the stars are Newtonian, it is found that the contribution by the small-scale gravitational fields to the macroscopic density and stress are, respectively, the Newtonian gravitational energy density and the Newtonian gravitational stress tensor. This result is based on the general-relativity field equation, not conservation laws, although the general-relativity field equation has the well-known property of being consistent with conservation laws.  相似文献   
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