A comparison of a gas chromatographic with electron-capture detection and a gas chromatographic with mass spectrometric detection screening methods for the analysis of famoxadone in grapes and wines

Famoxadone is a recent oxazolidinedione fungicide widely used in viticulture and in Integrated Pest Management strategies. In this work, after a simple and fast liquid-liquid extraction (LLE), two new gas chromatographic methods were developed to analyze famoxadone residues in grapes and wines, one with electron-capture detection (GC-ECD) and the other with mass spectrometry (GC-MS). Global uncertainties for validation parameters of both methods were compared. Limits of detection (LODs) were 0.06 and 0.02 mg/L, precision was not above 11.7 and 6.8% and recoveries were, on average, 103%+/-12 and 96%+/-12, respectively, for the GC-ECD and GC-MS methods. Similar expanded uncertainties in the range from 0.25 to 1.00 mg/L were below 35%, with increasing values for lower levels of famoxadone. GC-MS method had a lower LOD and a lower uncertainty if compared with the GC-ECD method.     

Determination of isoflavones in dietary supplements containing soy, Red Clover and kudzu: extraction followed by basic or acid hydrolysis

Isoflavones are phytochemicals found in many plants. Because of their structural similarity to beta-estradiol, health benefits of isoflavones have been evaluated in age-related and hormone-dependent diseases. Dietary supplement preparations contain extracts from soy, Red Clover and kudzu. Soy products contain primarily genistein, daidzein, and glycitein, while Red Clover products contain primarily formononetin and biochanin A. Kudzu extracts contain puerarin and daidzein among other components. Previous methods of analysis focused on the determination of isoflavones from a single botanical source, while dietary supplements are often a blend of extracts from different plants. We developed a method for the analysis of isoflavones in dietary supplements regardless of their botanical composition, using HPLC-PDA because of its applicability to routine analysis. Isoflavones are found as free compounds, glucoside derivatives, 6'-O-malonyl-beta-d-glucoside and 6'-O-acetyl-beta-d-glucoside derivatives. In this study, the samples were extracted at room temperature with 50:50 (v/v) MeCN/water, and then analyzed before and after hydrolyzing the isoflavones by acid or basic digestion. 2'-Methoxy-flavone and 6-methoxy-flavone were used as internal standards and were added together to every sample. Daidzein, glycitein, genistein, puerarin, calycosin, pratensein, pseudobaptigenin, formononetin, biochanin A and prunetin were among the isoflavones determined.     

Multifractal rainfall extremes: Theoretical analysis and practical estimation

We study the extremes generated by a multifractal model of temporal rainfall and propose a practical method to estimate the Intensity–Duration–Frequency (IDF) curves. The model assumes that rainfall is a sequence of independent and identically distributed multiplicative cascades of the beta-lognormal type, with common duration D. When properly fitted to data, this simple model was found to produce accurate IDF results [Langousis A, Veneziano D. Intensity–duration–frequency curves from scaling representations of rainfall. Water Resour Res 2007;43. doi:10.1029/2006WR005245]. Previous studies also showed that the IDF values from multifractal representations of rainfall scale with duration d and return period T under either d → 0 or T → ∞, with different scaling exponents in the two cases. We determine the regions of the (d, T)-plane in which each asymptotic scaling behavior applies in good approximation, find expressions for the IDF values in the scaling and non-scaling regimes, and quantify the bias when estimating the asymptotic power-law tail of rainfall intensity from finite-duration records, as was often done in the past. Numerically calculated exact IDF curves are compared to several analytic approximations. The approximations are found to be accurate and are used to propose a practical IDF estimation procedure.     

Time Scales in Polymer Modified Asphalts

Historically, Maxwell was probably the first one who recognized the importance of time scales for understanding the mechanical response of asphalt. In instantaneous response asphalt behaves as an elastic, solid-like material, on the other hand its long time response is that of a viscous, fluid-like material. In the linear viscoelastic region asphalt behaves as a low molecular weight polymer. However, in the nonlinear region of high strains or rates of strain the behavior of some asphaltic systems can be rather complicated. In asphalts, asphaltenes, resins and alkanes compose a complex colloidal system, in which alkanes act as a solvent, asphaltenes as micelles and the polar resins as stabilizers. In order to enhance the mechanical properties of asphalts they are frequently modified by blending them with appropriate polymers. Changes in the impermanent network that can be formed in some of these blends can lead to an unexpected behavior of the steady shear viscosity function. Several different time scales emerge from this behavior. A possible relation of these “nonlinear” time scales to the linear viscoelastic time scales is discussed and examples of anomalous behavior of polymer-modified asphalts are given.     

A Fully Magnetizing Phase Transition

We analyze the Farey spin chain, a one-dimensional spin system with long-range multibody interactions. Using a polymer model technique, we show that when the temperature is decreased below the (single) critical temperature T _c=1/2, the magnetization jumps from zero to one.