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Thermo-dielectric analysis
Part 2: Zeolites
By means of thermo-dielectric analysis, some natural and synthetic zeolites were studied (clinoptilolite, mordenite,X, Y andA). The results indicate the existence of two effects, one related to water evolution, reflected in a decrease of dielectric constant; the second peak is related to ionic conduction at high temperature. Both peaks characterize zeolites, in thermo-dielectric analysis.
Abstract
Knudsen mass-loss effusion technique was used for measuring the vapor pressures at different temperatures of the following crystalline compounds: diphenylacetic acid, between 357.27 and 379.08 K; triphenylacetic acid, between 418.98 and 436.97 K; 2,2-diphenylpropanoic acid, between 366.08 and 386.00 K; 3,3-diphenylpropanoic acid, between 366.09 and 386.03 K; 3,3,3-triphenylpropanoic acid, between 402.17 and 420.10 K. From the temperature dependence of the vapor pressure of each crystalline compound, the standard (p 0 = 105 Pa) molar enthalpies and Gibbs energies of sublimation, at T = 298.15 K, were derived. The measured thermodynamic properties are compared with literature results for phenylacetic and phenylpropanoic acids and correlations for estimation of the vapor pressures from the enthalpy of sublimation and the temperature of fusion of these and other compounds are presented.
Ear rots of maize caused by Fusarium spp. reduce grain yield and produce mycotoxins, which are harmful to humans and animals. To breed maize cultivars resistant to Fusarium spp., reliable large-scale phenotyping is essential. Our objectives were to (i) examine the precision of the ELISA method for determination of important mycotoxins, namely deoxynivalenol (DON) and fumonisins (FUM), (ii) evaluate the potential of near-infrared reflectance spectroscopy (NIRS) to estimate concentrations of DON and FUM in grain produced in inoculated maize plants, and (iii) compare the efficiency of ELISA, NIRS, and visual rating of disease severity for estimation of mycotoxin concentrations. Insignificant variation was observed between duplicate evaluations of DON and FUM by ELISA, showing the high repeatability of this method. DON and FUM determinations by ELISA were more closely correlated with mycotoxin concentrations predicted through NIRS than with visual rating of disease severity. For the prediction of DON, NIRS had very high magnitude of the coefficients of determination of calibration and cross validation (R 2 = 0.90–0.88). Thus, NIRS has a promising potential to predict DON concentration in grain samples of inoculated maize genotypes evaluated in resistance breeding programs.
