SAXS from a poly(amido-amine)-heparin complex in aqueous solutions: a comparison between two analysis methods

Summary Joerchel's method is applied to SAXS spectra of a poly(amido-amine)-heparin complex in aqueous non diluted solutions, showing a noticeable interference effect. The results are compared with those obtained by the classical Guinier analysis applied to diluted solutions of the complex.

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Zusammenfassung SAXS-Spektren eines Poly(amido-amin)-Heparin-Komplexes in nicht verdünnten wäßrigen Lösungen, die bemerkenswerte Interferenzeffekte zeigen, wurden mittels der Joerchel'schen Methode analysiert. Die Ergebnisse wurden mit den durch die klassische Analyse von Guinier an verdünnten wäßrigen Komplexlösungen erhaltenen verglichen.

     

Small angle X-ray scattering investigations on vinylpyridine-butadiene rubbers

Methylvinylpyridine-butadiene copolymers vulcanized by various α, ω dibromo-alkanes were investigated by X-ray small angle scattering. In these systems, employing the Hosemann-Joerchel analysis, only one cluster dimension of about 45 Å has been found with a polydispersity not exceeding 35 per cent. Stretched rubbers show interference effects both in the meridional and equatorial directions.     

Changes in superstructure of drawn isotactic polypropylene with annealing: A two-dimensional small-angle x-ray analysis

Two-dimensional small-angle x-ray (SAXS) analysis is extended and applied to isotactic polypropylene cold-drawn and annealed near the melting point. The SAXS intensity down to very small angles is detected by a high-resolution point-collimation camera. The SAXS fiber pattern, exhibiting only one meridional reflection and continuous scattering on the equator, shows that the microparacrystallites (“bricks” of the macrolattice) are densely packed together laterally into finite extended layers. The drawing process increases the ultrafibrillar characteristics of the samples and annealing increases their lamellar character. Annealing is carried out at a temperature near the melting point with the ends of the samples fixed so that recrystallization under strain takes place. The volume crystallinity increases on annealing from 32 to 57%. The SAXS results are in good agreement with NMR results; nevertheless the ideal paracrystal model assumption is, in the present case, not quite consistent with the results.     

A simple method for the determination of malachite green and leucomalachite green residues in fish by a modified QuEChERS extraction and LC/MS/MS

A simple method using LC/MS/MS was developed and validated to determine residues of malachite green (MG) and leucomalachite green (LMG) in fish fillet. A modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) technique was used to perform the sample preparation. The optimal extraction and cleanup conditions were established using an experimental design. The validation parameters obtained to determine both MG and LMG complied with the requirements established by regulatory agencies for the presence of such substances in fish, which establish that the method must attain, at least, a minimum required performance limit of 2 ng/g. The accuracy values ranged between 95 and 107%, and the precision values were lower than 11.2%. The method was used in the analysis of tilapia samples (n = 20) commercialized in Campinas, SP, Brazil. None of the samples presented detectable levels of MG or LMG residues.     

A X-ray line profile study on as-polymerized isotactic polypropylene

The line profile analysis of high-resolution wide angle X-ray diffraction spectra (WAXS) has been employed to characterize two polypropylenes polymerized by: a) “conventional” Ziegler-Natta catalyst (PP-A) and b) “high-yield” new supported catalyst (PP-B). The observed differences in line-width are most reasonably due to a marked crystallite size anisotropy, more pronounced for PP-A. The smallest size is along the crystallographic a-axis, which is the preferred direction of growth of crystallites. Paracrystalline fluctuations, on the whole larger in the high-yield polymer than in the conventional one, are present. The diffuse background resulting from line profile analysis is preliminarily investigated here in terms of scattering from a microcrystalline array.     

X-ray study of microstructure of slightly plasticized poly-(vinylchloride) (PVC)

Small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) as well as transmission electron microscopy (TEM) techniques have been applied to investigate the microstructure of a number of commercial poly-(vinylchloride) (PVC) samples, stretched 200% and annealed for 1 h at 110 °C. From SAXS analysis, the microstructure is described as an ensemble of quasi-spherical particles one-dimensionally ordered (in the fiber axis direction) and with large distance fluctuations in the equatorial plane. The superstructure is described as fibrillar or nematic-like. TEM micrographs confirm the SAXS data.SAXS meridional patterns present 001 and 003 reflections of Ca-stearate added as stabilizer to the samples, while WAXS profiles do not show any crystalline reflection of Castearate.An interaction of Ca-stearate molecules with PVC chains is postulated, which could partially account for the phenomenon called antiplasticization of PVC.     

Advanced x-ray study on crystalline and amorphous components of as-polymerized isotactic polypropylene

The WAXS powder pattern profile analysis of as-polymerized high-yield isotactic polypropylene has been performed in order to evaluate the crystalline, the so-called amorphous, and the diffuse scattering components. The amorphous component has been interpreted in terms of microcrystallites.The intensity percentages of the sample components are: -crystalline =42.12%, -semimicrocrystalline=18.65%, and -microcrystalline=39.23%. The method allows a good evaluation of the anisotropic structural disorder as well as the crystallite dimensions anisotropy and crystallinity determination. Moreover, the contemporary occurrence of different crystalline modifications in the sample can be defined quantitatively.The crystallinity, expressed as the ratio between the integral intensities diffracted by the large -form crystallites plus the middle-size -form crystallites and the sum of the larger and smaller ones is 61%.