Comparison of capillary gas chromatographic method and automated spectrophotofluorometric methods for measuring content uniformity of conjugated oestrogens in pharmaceutical preparations

To measure the content uniformity of conjugated cestrogens tablets, the USP XXII monograph specifies a capillary gas chromatographic method. This involves separation of the trimethylsilyl derivatives of the various oestrogens found in a typical conjugated oestrogens tablet using a fused-silica 0V 225 bonded phase column. Hydrogen is used as the carrier gas with FID detection. A more rapid spectrophotofluorometric method of analysis has been developed in which the oestrogens are extracted from the dosage form into water, then transferred into organic solvent as the dicyclohexylamine complex. Fluorescence is developed by heating the solution of the complex in the presence of 70% sulphuric acid. The chemistry and detection are carried out using a segmented-flow analyser.The spectrophotofluorometric method is preferred as a routine control for content uniformity because considerable time is saved during sample preparation and analysis compared to gas chromatography. Coefficients of variation show that both methods produce acceptable results. These results fall well within the USP XXII [1] monograph, limits and also well within the tighter limits imposed by the USP XXII, section 905.     

Orientation effects during the flow of short-fibre reinforced thermoplastics

A study has been carried out to investigate molecular orientation in injection moulded bars of short glass fibre reinforced polypropylene and polyethylene. For the range of fibre concentrations encountered commercially, the fibres do not appear to have any direct effect on the matrix orientation. As the fibre concentration increases, however, the matrix orientation becomes dominated by the orientation of the fibres. These effects are interpreted in terms of current ideas of the rheology of polymer melts during injection moulding and the crystallization of polymers at fibre surfaces.     

Dressing plasmons in particle-in-cavity architectures

Placing metallic nanoparticles inside cavities, rather than in dimers, greatly improves their plasmonic response. Such particle-in-cavity (PIC) hybrid architectures are shown to produce extremely strong field enhancement at the particle-cavity junctions, arising from the cascaded focusing of large optical cross sections into small gaps. These simply constructed PIC structures produce the strongest field enhancement for coupled nanoparticles, up to 90% stronger than for a dimer. The coupling is found to follow a universal power law with particle-surface separation, both for field enhancements and resonant wavelength shifts. Significantly enhanced Raman signals are experimentally observed for molecules adsorbed in such PIC structures, in quantitive agreement with theoretical calculations. PIC architectures may have important implications in many applications, such as reliable single molecule sensing and light harvesting in plasmonic photovoltaic devices.     

Defining the nanostructured morphology of triblock copolymers using resonant soft X-ray scattering

The morphologies of a poly(1,4-isoprene)-block-polystyrene-block-poly(2-vinyl pyridine) (IS2VP) copolymer were investigated using resonant soft X-ray scattering (RSoXS) together with scanning force microscopy, small-angle X-ray scattering, and electron microscopy. Differences in the nanoscopic morphologies in the bulk and thin film samples were observed arising from the competition between segmental interactions between the blocks and the substrate and the surface energies of each block. Using soft X-rays at selected photon energies to isolate the scattering contribution from different polymer blocks, RSoXS unambiguously defined the complex morphology of the triblock copolymer. In the bulk sample, two nested, hexagonal arrays of P2VP and PI cylindrical microdomains residing in the PS matrix were observed. The cylindrical microdomains of one component were found to be located at the interstitial sites of the hexagonal array of the other component that has the larger d spacing. In solvent-annealed thin films with 40 nm in thickness, a hexagonal array of core-shell microdomains of P2VP cores with PS shells that reside in a PI matrix were observed.     

Effect of the dielectric-substrate interface on charge accumulation from vacuum ultraviolet irradiation of low-k porous organosilicate dielectrics

We compare the effect of various dielectric-substrate interfaces on charge accumulation during vacuum ultraviolet irradiation of capped low-k porous organosilicates to find that more charges are trapped in a dielectric stack deposited on silicon compared with the same stack deposited on copper. Insertion of a 5-nm interfacial thermal oxide layer further increases the amount of trapped charges in the dielectric. The difference between the photoemission and injection currents determines the number of charges trapped in the dielectric as a result of irradiation. Fewer charges are trapped when the injection current increases.     

Preparation and properties of stereoregular poly(hydroxyethyl methacrylate) polymers and hydrogels

Linear poly(hydroxyethyl methacrylate) (PHEMA) has been synthesized in highly syndiotactic and highly isotactic configurations. The high syndiotactic PHEMA prepared by u.v. photolysis at ?40° C was found by ¹³C n.m.r. to have a tactic triad content of 84% syndio, 16% hetero and 0% iso. High isotactic PHEMA was prepared by anionic polymerization of benzoxyethyl methacrylate in toluene followed by selective hydrolysis of the benzoate ester, and was observed by ¹³C n.m.r. to have a 5% syndio, 15% hetero and 80% isotactic triad content. A linear PHEMA polymer formed by radical polymerization at 60°C in ethanol solvent was found to have a tactic triad content of 58% syndio, 42% hetero and 0% iso. These polymers have been crosslinked with hexamethylene diisocyanate and their water swelling properties determined as functions of temperature and crosslinker concentration. Isotactic PHEMA exhibited greater aqueous swelling below 30° C than the syndiotactic PHEMA samples. The stereochemistry of the polymer chain is shown to be a factor in determining the swelling behaviour of hydrophilic methacrylate gels.     

Photochemical degradation of glassy polyesters of low softening point

The photodegradation of polyesters prepared by the reaction of o-phthalic, adipic, and “dimer” acids with ethylene glycol has been studied. The polyesters softened at temperatures in the range of 25–50°C. Polymer films were irradiated in air by means of a medium pressure mercury lamp and the extent of formation of COOH groups determined by infrared spectroscopy. The films were also irradiated in vacuo and in air by means of a high-pressure mercury lamp, and the volatile products, consisting mainly of carbon monoxide and carbon dioxide, were determined by gas chromatography. The results are interpreted in terms of simultaneous Norrish type I and type II decompositions of the polyesters. The type I process accounts for the formation of carbon monoxide and carbon dioxide in the absence of air. The enhanced yield of carbon dioxide in irradiations performed in air is ascribed to the formation of hydroperoxide which undergoes further photolysis. The type II process accounts for the formation of COOH groups. The photodegradation of these glassy polyesters parallels that of crystalline poly(ethylene terephthalate) and is relatively unaffected by changes in composition of the aromatic polyester.     

Vestitol: A phytoalexin with insect feeding-deterrent activity

A major feeding deterrent forCostelytra zealandica larvae was isolated from the root of the resistant pasture legumeLotus pedunculatus and was identified as 3R-(—)-vestitol. This compound was also identified in feeding deterrent-activeL. pedunculatus leaf extracts. (—)-Vestitol and a secondLotus isoflavan, sativan, have been reported to have phytoalexin activity, and the implications of this for the study and understanding of insect resistance are briefly discussed.     

CASTING CHARACTERISTICS OF CLAYS: I,IMPROVED METHODS FOR DETERMINATION*

Part I of this investigation covers the development of reliable laboratory tests to indicate the relative properties of different clays with the primary consideration of their casting behavior. Methods are given for the determination of casting rate, permeability, water retention, fluidity, thixotropy, organic content, shrinkage, and dry strength. By determining the effect of varying increments of electrolyte on the foregoing properties, it is possible to select clays which have desirable casting characteristics for commercial use. Samples of fast- and slow-casting kaolins and ball clays were used to indicate the utility of the methods employed; results are also given for two composite bodies. In developing the test procedures using the Büchner funnel (vacuum), the effect of the following factors was determined: mixing procedure, ratio of clay to flint, feldspar vs. flint as the nonplastic, electrolyte content, quantity of slip used, specific gravity of slip, slip temperature, aging, and vacuum pressure; The optimum procedure for testing clays was then evolved. Part II and Part III of this series of studies are in preparation for publication.