Photometrische Wismutbestimmung mit Brenzcatechinviolett

Zusammenfassung Es wurden die Bedingungen der photometrischen Wismutbestimmung mit Brenzcatechinviolett bei der WellenlÄnge _max=580 nm ausgearbeitet und der Einflu\ der Fremdionen untersucht. Das Lambert-Beersche Gesetz gilt in den Konzentrationsgrenzen 0,0–6,2 g Bi/ml bei 1,6 cm Schichtdicke.

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Summary A method is given for the photometric determination of bismuth using pyrocatechol violet, at the wave-length of _max=580 nm. Interferences by foreign ions have been examined. Beer's law is obeyed from 0.0 to 6.2 g Bi/ml (1,6 cm cuvettes).

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Als erste Mitteilung dieser Reihe soll die Arbeit: Malát, M.: Naturwissenschaften 48, 569 (1961) betrachtet werden.     

Modelling,optimisation and control of selectivity in the separation of aromatic bases by electrokinetic chromatography using a neutral cyclodextrin as a pseudostationary phase

A simple mathematical model describing the separation of a series of aromatic bases by electrokinetic chromatography using beta-cyclodextrin (beta-CD) as a pseudostationary phase is described. The model takes into account changes in electrolyte pH and the different formation constants between the neutral and charged forms of the analytes with the CD. Constants in the model were obtained within the two-dimensional experimental space defined by pH and [beta-CD] with nonlinear regression using only five experimental points. These constants agreed with expected trends in analyte-CD interactions and predicted much higher formation constants for the neutral analyte-CD complex than for the charged analyte-CD complex. Correlation between predicted and observed mobilities using additional 20 points within the experimental space gave r(2) = 0.995. Optimisation of the pH and [beta-CD] was performed using both the normalised resolution product and minimum resolution product criteria and provided two optimum separations which exhibited different selectivities. Differences between predicted and observed migration times at these optima were less than 2.5 and 5% for the normalised resolution product and the minimum resolution criteria, respectively. In both cases the correct migration order was predicted. The model was also applied successfully to the optimisation of conditions for the separation of a specific mixture of analytes or for conditions under which particular analytes migrated in a desired order.     

On-line coupling of capillary isotachophoresis and zone electrophoresis for the assay of phenolic compounds in plant extracts

The combination of capillary isotachophoresis (ITP) and capillary zone electrophoresis (CZE) in the column coupling configuration was optimized in a mode where the electrolyte for the CZE step is different from the leading and terminating ITP electrolytes. Two colored markers, picric acid and 1-nitroso-2-naphthol, were used for exact timing of the transfer of isotachophoretically stacked analyte zones into the CZE column and for the control of the residual amount of the leading and terminating ITP electrolytes entering the CZE capillary together with the analytes, thus controlling the duration of transient ITP migration in the CZE capillary and ensuring good separation of the analytes and reproducibility of the migration times (relative standard deviations 1%). ITP-CZE was applied to the simultaneous assay of several cinnamic acid derivatives and flavonoids in methanolic extracts of Sambucus flowers and Crataegus leaves and flowers. The preconcentrating and cleansing effect of the ITP step allowed injection of relatively large sample volumes (30 microL). The limits of detection were approximately 20-50 ng x mL(-1) and 100 ng x mL(-1) for the acids and flavonoids, respectively ( thick similar 200-times lower compared to conventional CE) with spectrophotometric detection at 254 nm. The ITP-CZE exhibited satisfactory linearity and precision when using CZE buffer of pseudo "pH" 9.0; 1-nitroso-2-naphthol was employed as the internal standard. The separation took approximately 35 min. The ITP-CZE results for rutin, hyperoside, and vitexin-2-O"-rhamnoside were in good accordance with those obtained previously by high-performance liquid chromatography.     

On the Hahn-Banach Extension Property in Hardy and mixed norm spaces on the unit ball

For a nonempty setE of nonnegative integers letH _E ^{p, q, a} andH _E ^p be the closed linear span of

Rapid determination of 90Sr in urine samples using AnaLig® Sr-01

This paper describes the use of IBC’s AnaLig^® Sr-01 molecular recognition technology product to effectively and selectively pre-concentrate, separate, and recover strontium from urine samples. This method uses two-stage columns separation consisting of two different commercial products Eichrom’s Pre-filter Material and AnaLig^® Sr-01 column from IBC Advanced Technologies. This method does not involve co-precipitation of strontium as phosphates and oxalates from urine samples. The new rapid method separates strontium-90 with high chemical recovery.     

Allyl sulfides and α‐substituted acrylates as addition–fragmentation chain transfer agents for methacrylate polymer networks

The rapid and uncontrolled nature of network formation from di(meth)acrylate monomers produces high shrinkage stress and results in polymers with oftentimes brittle mechanical properties. Methods for regulating polymerization and network formation are sought. One option is the use of addition–fragmentation chain transfer (AFCT) agents, which are well known to control molecular weight and molecular weight distribution of monofunctional (meth)acrylates. A series of novel and previously described AFCT reagents were synthesized and screened with laser flash photolysis to determine reactivity. Well‐performing AFCT reagents were then tested in polymerizations with monofunctional and difunctional methacrylates. With monofunctional monomers, the molecular weight and polydispersity of the resultant linear polymers tend to decrease with the addition of AFCT agent. In copolymerization with dimethacrylate monomers, the AFCT agents were found to substantially lower and sharpen the glass transition. Sharpness of the glass transition is here indicative of a more regular and homogenous network. After coupling of the instruments, photorheology was performed simultaneously with real‐time IR to show an increase in monomer conversion at the time of gelation, which appears to have a positive effect on reducing shrinkage stress. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 394–406     

Poly(2‐oxazoline) hydrogels crosslinked with aliphatic bis(2‐oxazoline)s: Properties,cytotoxicity, and cell cultivation

A series of hydrogels from 2‐ethyl‐2‐oxazoline and three bis(2‐oxazoline) crosslinkers—1,4‐butylene‐2,2′‐bis(2‐oxazoline), 1,6‐hexamethylene‐2,2′‐bis(2‐oxazoline), and 1,8‐octamethylene‐2,2′‐bis(2‐oxazoline)—are prepared. The hydrogels differ by the length of aliphatic chain of crosslinker and by the percentage of crosslinker (2–10%). The influence of the type and the percentage of the crosslinker on swelling properties, mechanical properties, and state of water is studied. The equilibrium swelling degree in water ranges from 2 to 20. With a proper selection of the crosslinker, Young's modulus can be varied from 10 kPa to almost 100 kPa. To evaluate the potential for medical applications, the cytotoxicity of extracts and the contact toxicity toward murine fibroblasts are measured. The hydrogels with the crosslinker containing a shorter aliphatic exhibit low toxicity toward fibroblast cells. Moreover, the viability and the proliferation of pancreatic β‐cells incubated inside hydrogels for 12 days are analyzed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1548–1559     

New antiferroelectric liquid crystalline materials containing a keto group and two lactate groups

New chiral liquid crystalline materials containing a keto group and two lactate units attached to the mesogenic core have been synthesized and studied. All the new compounds show the paraelectric SmA, ferroelectric SmC* and antiferroelectric SmC*_A phases each over rather broad temperature ranges. The properties of the phases were characterized by DSC, electro-optical and dielectric studies. The spontaneous polarization, tilt angle, helical pitch, and switching times were determined for the polar phases.