Preparation of polyethyleneglycol (PEG) coatings for microencapsulation of charcoal

Polyethyleneglycols (PEGs) with their high solubility in water cannot normally be used as a coating material in aqueous solutions such as blood. A λ-radiation procedure was therefore applied after coating charcoal granules with PEG in a non-aqueous phase, and an 80–90% insoluble polymer matrix on charcoal was obtained. PEGs with different molecular weights from 4000 to 300,000 were used for coating. The performance of this system was determined by using several test solutes, namely creatinine, uric acid, and vitamin B-12. It was observed that the pore size and structure of these membranes can be adjusted by changing the irradiation time and by using PEGs with different molecular weights. Thus, very high mass transfer rates can be achieved.     

Tailor-made agarose-based reactive beads for hemoperfusion and plasma perfusion

Composite beads of approximately 1mm diameter, made of cross-linked agarose and containing Fuller’s Earth or zirconium oxide powders, were prepared and used in extracorporeal systems for blood detoxification. The former was used for the removal of Paraquat, while the latter was used to remove inorganic phosphate from hyper-phosphatamic animals with or without acute renal failure. The high surface area of the powder, combined with the low resistance to diffusion in the cross-linked agarose matrix, are highly advantageous. The crosslinking provides high mechanical strength, heat stability, prolonged shelf life, good blood flow characteristics, and prevents the release of fine particles into the blood. Crosslinked agarose beads of 1 mm diameter, containing chemically-bound heparin were also prepared, and used as a model for direct contact removal of LDL-cholesterol from the blood of familial hypercholesterolemic patients by hemoperfusion. The high capacity of these beads (over 5 mg LDL/mL beads) indicates that this clinical modality can replace the highly expensive plasmapheresis procedure presently used.     

An orally administered microcapsule system for treating chronic renal failure patients

Ingestible adsorbents for the removal of uremic metabolites are being investigated as adjunctive therapy in the treatment of chronic uremia. In particular, a microcapsule product containing urease and zirconium phosphate (UZP) has been investigated for removing urea. A dog model, simulating chronic uremia, was developed to investigate: (1) the concentration of various nitrogenous metabolites (urea, creatinine, and uric acid) in the GI tract, (2) flux rates of H₂O and various nitrogenous metabolites in the GI tract, and (3) the efficacy of the microcapsule product. The results of these perfusion studies suggest that urea and creatinine can be removed from the GI tract via ingestible adsorbents. In addition, the model may be useful in investigating suspect uremic toxins, e.g., guanidinosuccinic acid (GSA). The reduction of blood urea nitrogen levels in the dog model when the animal was fed the microcapsule product was limited by the capacity of the zirconium phosphate to bind ammonium ion. Preliminary clinical studies with the microcapsule product indicate that it may be of potential adjunctive therapy in patients suffering from chronic renal failure.     

Quantification of reduced glutathione by HPLC-UV in erythrocytes of hemodialysis patients

Reduced glutathione (GSH) is a well-known multifunctional antioxidant. Its depletion is linked to a number of pathologies, such as renal insufficiency. Feasible methodologies in clinical chemistry are vital. Therefore a methodology for GSH quantification was optimized and validated by HPLC-UV. Important aspects such as acid deproteinization and GSH stability were established. The erythrocytes were hemolyzed, deproteinized, derivatized with 5,5-dithio-bis (2-nitrobenzoic) acid and analyzed using HPLC, on an RP18 gradient elution, lambda=330 nm. The method was applied to hemodialysis patients (n=75) compared with healthy subjects (n=40). The assay was linear from 0.5 to 3.0 mm (r2>0.99). The intra- and inter-run reproducibilities were obtained with CV%<10%. The accuracy (bias %) ranged from 1.32 to -6.38%, and the recovery was >94%. The derivatized sample was stable for 60 days at -20 degrees C. The GSH levels in hemodialysis patients showed a significant increase compared with healthy subjects (p<0.05) and an inverse correlation with age (r=-0.286; p=0.013) was found. This method used UV detection, reduction of the phosphate concentration in the mobile phase and effective protein removal with trichloroacetic acid. The method proved to be reproducible, precise, accurate and stable. Thus, it can be suggested for routine laboratory tests for the verification of physiopathological conditions.     

Alpha and gamma spectrometry for determination of natural and artificial radionuclides in tea, herbal tea and camomile marketed in Italy

Several kinds of tea, camomile and herbal tea were analysed to determine natural and artificial radioactivity. The radionuclides were determined by alpha (²¹⁰Po) and gamma (²²⁸Ac, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb, ⁴⁰K and ¹³⁷Cs) spectrometry. ²²⁸Ac ranged between 0.6 and 9.0 Bq kg⁻¹_dry; ²¹⁰Po between 1.90 and 36.1 Bq kg⁻¹_dry; ²¹⁴Pb and ²¹⁴Bi between 0.7 and 4.9 Bq kg⁻¹_dry; ²¹⁰Pb between < 10.0 and 58.9 Bq kg⁻¹_dry; ⁴⁰K between 463 and 936 Bq kg⁻¹_dry; ¹³⁷Cs between < 0.3 and 2.6 Bq kg⁻¹_dry. The percentage of ²¹⁰Po extraction in infusion was also determined; the arithmetical mean value of percentage of ²¹⁰Po extraction resulted 20.7 ± 7.50.     

Impact of Solvent and Their Contaminants on Pd/C Catalyzed Suzuki-Miyaura Cross-Coupling Reactions

The aim of this work was to understand if solvent contaminants can interfere in Suzuki’s cross-coupling reactions and if it can explain the lack of robustness in industrial processes. For this purpose, several parameters were tested on the industrial model reaction between 2-bromonaphthalene and phenylboronic acid catalyzed by Pd/C. Best results were obtained using THF as solvent. Traces of the precursors of the used solvents, such as 2,3-dihydrofurane or maleic anhydride (100–300 ppm related to the solvent) strongly poisoned the reaction, decreasing the conversion significantly. This means that to ensure robust production, solvent quality must be analyzed at the ppm level. Fortunately, addition of triphenylphosphine can circumvent the catalyst poisoning.     

Artificial red cells with crosslinked hemoglobin membranes

Artificial cells containing concentrated hemoglobin (Hb) solution were prepared by interfacial polymerization of Hb with glutaraldehyde (GA) in liquid membrane capsules (LMC). A solution containing 30% of Hb was emulsified in mineral oil as red cell-size microdroplets, and this emulsion was dispersed in an aqueous phase containing glutaraldehyde to form LMC. The LMC were semipermeable templates that held the microdroplets of Hb in suspension while GA diffused through the oil to the microdroplet surfaces. The GA crosslinked Hb at the surface of each microdroplet to form an artificial red-cell membrane encapsulating Hb solution. A water-soluble surfactant was used to eject the cells from the LMC and suspend them in saline. Several surfactants were evaluated. Cell size was controlled by agitation speed during preparation of the original emulsion. Cells of 2.52 = ±1.69 μm were prepared. The encapsulated Hb retained capacity to bind and release O₂. The cells had aP ₅₀ of 8.9 torr (1200 Pa) and a capacity of 0.55 cc O₂/g of total Hb, indicating that the crosslinked portion of the Hb did not contribute to O₂ transport.     

Magnetic properties of La0.5−xLnxSr0.5MnO3 (Ln=Pr, Nd, Gd and Y)

Magnetic and electron transport properties of four series of manganates of the composition La_0.5−xLn_xSr_0.5MnO₃ (Ln=Pr, Nd, Gd and Y) have been investigated to examine how the ferromagnetic metallic nature of the parent La compound changes over to antiferromagnetic insulating behavior, with change in Ln and x due to the associated changes in the A-site cation radius as well as the size disorder. When Ln=Pr and Nd, there is a transition from the tetragonal I4/mcm structure to the orthorhombic Immm and Imma structures at x=0.2 and 0.35, respectively. There is a gradual evolution of the properties from those of La_0.5Sr_0.5MnO₃ to those of Pr_0.5Sr_0.5MnO₃ or Nd_0.5Sr_0.5MnO₃ with increase in x. Thus, when x>0.2 and >0.35, respectively, the Pr- and Nd-substituted manganates show ferromagnetic transitions followed by antiferromagnetic transitions at low temperatures, with the ferromagnetic T_C decreasing with increasing x. The Gd and Y series of compounds are all orthorhombic and show a decrease in T_C with the increase in x, the ferromagnetism disappearing at high x. At a value of x corresponding to the A-site cation radius of Pr_0.5Sr_0.5MnO₃, the Gd and Y series of compounds exhibit ferromagnetism in the 250-300 K region and undergo an antiferromagnetic transition on cooling. The T_C−T_N gap is sensitive to the disorder arising from the size mismatch.     

Headspace gas chromatographic determination of ethylene oxide in air

Summary A simple and accurate headspace-GC method is described to determine the amount of ethylene oxide which has been collected from air using adsorption tubes containing activated charcoal and a relatively safe desorbing agent (N,N-dimethyl acetamide). The detection limit is 40μg/m³.     

The evolution of steep fronts in non-fickian polymer-penetrant systems

We adapt a recently proposed model for non-Fickian diffusion of penetrants into polymers and use it to study a drug-delivery problem. The model modified Fick's diffusion equation by the addition of stress-induced flux. A stress evolution equation incorporating aspects of the Maxwell and Kelvin-Voigt viscoelastic stress models completes the model. The relaxation time in the polymer is taken as a function of the penetrant concentration. The system is studied under the assumption that the diffusivity is large. Singular perturbation techniques are used to show that the concentration and stress evolve diffusively for small time, but exhibit steep fronts in a narrow region within the domain for larger time. These predictions are verified numerically for specified parameter values. Finally, the equations are studied in the steady state and are found to predict the evolution of shocks.     

Present state of teaching Analytical Chemistry in Hungary

Summary A review is given on the present state and characteristic features of the higher education system in Hungary with special regard to Analytical Chemistry. Similarities and differences between science university and technical university education are shown. Problems of teaching instrumental analysis and of specialization are discussed.Presented at Euroanalysis III conference, Dublin, August 20–25, 1978     

Potentiometric Na+, K+, Ca2+, and Cl? determination of serum and whole blood in comparison to routine clinical laboratory methods

Ohne ZusammenfassungSupported by a grant of the DFG; SFB 89-Cardiology, Göttingen.     

Plastic deformation mechanisms in polyimide resins and their semi-interpenetrating networks

The plastic deformation mechanisms in both thermoplastic and thermoset polyimide resins and their semi-interpenetrating networks (semi-IPNs) were investigated. The fundamental tendency to undergo strain localization (crazing and shear banding) as opposed to a more diffuse (or homogeneous) deformation in these polymers was evaluated. In situ polarized light microscopic observation of crack-tip deformation mechanisms in solvent-cast films was conducted with a miniature testing device attached to the microscope stage. NASA LaRC TPI, a thermoplastic polyimide, was found to exhibit combined shear yielding and crazing under plane-stress loading conditions. Contrarily, NR-150B2 thermoplastic polyimide exhibited diffuse shear yeilding; no shear banding or crazing was found near the crack tip. Adding a small amount of thermoplastic component, either NR-150B2 or LaRC TPI, was found to raise considerably the fracture toughness of PMR-15 thermoset PI. PMR-15 thermoset films also showed diffuse shear yielding, albeit with a much smaller deformation zone. This was consistent with its low toughness and could be understood on the basis of a limited extensibility of a highly crosslinked network. Numerical calculations were performed to confirm this low value of network chain draw ratio. The dimensions of the deformation zone ahead of the crack tip in a semi-IPN with a thermoset matrix were increased as a higher weight fraction of the thermoplastic component was added. The deformation zone size of a thermoplastic matrix was found to decrease with an increasing amount of thermoset PMR-15. Deformation also became more diffuse with a higher PMR-15 content in LaRC TPI. Fracture toughness variations can be correlated with deformation size changes in these semi-IPNs.     

The effect of annealing on slow crack growth in an ethylene-hexene copolymer

A quenched ethylene-hexene copolymer was annealed in the temperature range of 86 to 127°C. The morphological changes were monitored by differential scanning calorimetry (DSC) and density. The slow crack growth resistance tested at 80°C was a maximum at an annealing temperature of 113°C and a minimum of 123°C. The lifetimes can be varied by more than a factor of 20 depending on the thermal treatment. The increase in slow crack growth resistance between 86 and 113°C is attributed to an increase in the strength of the crystals by becoming more perfect and to the conversion of loose tie molecules into taut tie molecules. The decrease in strength between 113 and 123°C is attributed to the decrease in tie molecules when a large fraction of the as-quenched crystals begin to melt.     

Gas permeability and permselectivity of fluorinated polybenzoxazoles

Gas permeability and permselectivity are investigated for polybenzoxazoles from bis(3-amino-4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (BAHHP) and aromatic diacid chlorides. Effects of thermal cyclization on the permeation properties are also investigated. The polybenzoxazole from BAHHP and 4,4′-(1,1,1,3,3,3-hexafluoroisopropylidene)dibenzoyl chloride (HFDB) displays high performance for CO₂/CH₄ separation ( $ {\rm P}_{{\rm CO}_2 } $ = 6.1 × 10^?9 cm³ (STP) cm^?1 s^?1 cm-Hg^?1, and $ {{{\rm P}_{{\rm CO}_2 } } \mathord{\left/ {\vphantom {{{\rm P}_{{\rm CO}_2 } } {{\rm P}_{{\rm CH}_4 } }}} \right. \kern-\nulldelimiterspace} {{\rm P}_{{\rm CH}_4 } }} $ = 38 at 35°C). The polybenzoxazole from BAHHP and 2,6-naphthalene dicarbonyl chloride displays high performance for H₂/CO or H₂/CH₄ separation ( $ {\rm P}_{{\rm H}_2 } $ = 2.4 × 10^?9 cm³ (STP) cm^?1 s^?1 cm-Hg^?1, $ {{{\rm P}_{{\rm H}_2 } } \mathord{\left/ {\vphantom {{{\rm P}_{{\rm H}_2 } } {{\rm P}_{{\rm CO}} }}} \right. \kern-\nulldelimiterspace} {{\rm P}_{{\rm CO}} }} $ = 71, and $ {{{\rm P}_{{\rm H}_2 } } \mathord{\left/ {\vphantom {{{\rm P}_{{\rm H}_2 } } {{\rm P}_{{\rm CH}_{\rm 4} } }}} \right. \kern-\nulldelimiterspace} {{\rm P}_{{\rm CH}_{\rm 4} } }} $ = 250). Permeation properties for the polybenzoxazole from BAHHP and HFDB are close to those for a polyimide of similar chemical structure. The permeation properties are discussed in connection with packing density and local segmental mobility. © 1992 John Wiley & Sons, Inc.     

The in situ reactive compatibilization of nylon-6/polystyrene blends using anhydride functionalized polystyrenes

Nylon-6/polystyrene (PS) blends were reactively compatibilized by addition of various anhydride functionalized polystyrenes. The morphology of the blends was examined using a scanning electron microscopy (SEM) technique. The particle size of the dispersed styrenic phase was about 3.2 μm for the uncompatibilized 8/2 Nylon-6/PS blend while those of the compatibilized blends were decreased by as much as two orders of magnitude depending on the amount and type of the functionalized polystyrene (FPS) added. Several low-molecular weight polystyrenes with terminal anhydride groups, prepared by two different functionalization methods, were examined. The effect of molecular weight on particle size reduction depended on the basis of comparison, mass of additive, or moles of anhydride units. A high-molecular weight random copolymer of styrene and maleic anhydride was most effective when compared on a mass basis. The increase in adhesion between the Nylon-6 and the styrenic phases caused by the in situ reaction was evaluated by a lap shear technique. The free polystyrene, Nylon-6, and Nylon-FPS copolymer formed were separated by solvent extraction technique using formic acid and toluene. The extent of coupling reaction between the functionalized polystyrenes and Nylon-6 ranged from 25 to 43%. © 1992 John Wiley & Sons, Inc.     

Direct AAS determination of Co, Cr, Cu, Mn and Ni in U3O8 by electrothermal atomization

Summary An atomic absorption spectrometric method has been developed for the determination of chromium, cobalt, copper, manganese and nickel in U₃O₈ by electrothermal atomization of 5 mg powder samples. Nanogram amounts of all the elements can be estimated with a precision ranging between 7–12%. The non-specific absorption due to U₃O₈ for these measurements is negligible. The use of graphite powder with U₃O₈ in equal or double the sample amount improves sensitivity for the analyte element and prolongs the life of the atomizer.

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Direkte AAS-Bestimmung von Co, Cr, Cu, Mn und Ni in U₃O₈ durch elektrothermische Atomisierung

Zusammenfassung Das entwickelte AAS-Verfahren geht von pulverförmigen 5mg-Proben aus. Nanogramm-Mengen der genannten Elemente können mit einer Genauigkeit im Bereich von 7–12% bestimmt werden. Die durch U₃O₈ verursachte unspezifische Absorption ist zu vernachlässigen. Durch Graphitzusatz (in der gleichen oder doppelten Menge der Probe) wird die Empfindlichkeit der Bestimmung verbessert und die Lebensdauer des Atomizers verlängert.

     

Influence of concentration on the activation energy for diffusion in polymer-solvent systems

The self-diffusion of benzene, toluene, and ethylbenzene in polystyrene have been analyzed using the Vrentas/Duda free-volume diffusion model. Diffusion coefficient predictions suggest an exponential concentration dependence of the activation energy required to overcome attractive forces, E. Without the use of any diffusion data approximating E as zero over the entire concentration range yields self-diffusion coefficient predictions which are in good agreement with experimental data. © 1992 John Wiley & Sons, Inc.     

Analysis of Volatile Molecules Present in the Secretome of the Fungal Pathogen Candida glabrata

Candida albicans, Candida glabrata, Candida parapsilosis and Candida tropicalis are the four most common human fungal pathogens isolated that can cause superficial and invasive infections. It has been shown that specific metabolites present in the secretomes of these fungal pathogens are important for their virulence. C. glabrata is the second most common isolate world-wide and has an innate resistance to azoles, xenobiotics and oxidative stress that allows this fungal pathogen to evade the immune response and persist within the host. Here, we analyzed and compared the C. glabrata secretome with those of C. albicans, C. parapsilosis, C. tropicalis and the non-pathogenic yeast Saccharomyces cerevisiae. In C. glabrata, we identified a different number of metabolites depending on the growth media: 12 in synthetic complete media (SC), 27 in SC-glutamic acid and 23 in rich media (YPD). C. glabrata specific metabolites are 1-dodecene (0.09 ± 0.11%), 2,5-dimethylundecane (1.01 ± 0.19%), 3,7-dimethyldecane (0.14 ± 0.15%), and octadecane (0.4 ± 0.53%). The metabolites that are shared with C. albicans, C. glabrata, C. parapsilosis, C. tropicalis and S. cerevisiae are phenylethanol, which is synthesized from phenylalanine, and eicosane and nonanoic acid (identified as trimethylsilyl ester), which are synthesized from fatty acid metabolism. Phenylethanol is the most abundant metabolite in all fungi tested: 26.36 ± 17.42% (C. glabrata), 46.77 ± 15.58% (C. albicans), 49.76 ± 18.43% (C. tropicalis), 5.72 ± 0.66% (C. parapsilosis.) and 44.58 ± 27.91% (S. cerevisiae). The analysis of C. glabrata’s secretome will allow us to further our understanding of the possible role these metabolites could play in its virulence.