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141.
Andrzej Swinarew Beata Piekarnik Zbigniew Grobelny Andrzej Stolarzewicz Jurate Simokaitienė Egle Andrikaityte Juozas V. Gražulevičius 《Macromolecular Symposia》2011,308(1):8-11
Summary: The polymerization of (9-carbazolyl)methylthiirane in the presence of cyclic oligo(potassium glycidoxide) as the macroinitiator activated 18-crown-6 leads to polythioether with the molecular masses relatively near to the calculated ones. This polythioether dispersed in a commercially available transparent polymer gives a new blue photoluminescent material. 相似文献
142.
Kolakowski BM McCooeye MA Mester Z 《Rapid communications in mass spectrometry : RCM》2006,20(22):3319-3329
The separation and ion focusing properties of High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) depend on desolvated ions entering the device, leading to a compound-specific, reproducible compensation voltage (CV) for each ion. This study shows that the conditions identified for stable spray and satisfactory ion desolvation in normal electrospray ionization mass spectrometry (ESI-MS) operation might significantly differ from those required for FAIMS-MS. In a typical setup with high-flow electrospray conditions, ions could be incompletely desolvated, resulting in the formation of unidentified clusters with differing behavior in a FAIMS environment. This causes compound-specific shifts of as much as 10 V in CV values when the mobile phase composition and/or flow rate are varied. The shifts diminish and finally disappear when the flow rate of methanol, used as mobile phase, is reduced to 40 microL/min and that of acetonitrile to 20 microL/min. The reproducibility of the observed CV was determined by scanning the CV while infusing a five-component mixture into a 400 microL/min flow of methanol or 50:50 acetonitrile/water. The relative standard deviation (RSD) for these multiple scans ranged from 0.7% to 6%. Therefore, under a constant set of experimental parameters, the CV does not shift appreciably. These observations have an impact on method development strategies. High flow rates can be used with the FAIMS device, since the CV values are reproducible, but it is likely that clusters are forming. Therefore, CV scans should be performed under conditions which mimic the chromatographic elution or flow injection analysis conditions, including matrix composition, to minimize errors in CV determination. An alternative approach is to determine the liquid flow rate at which the CV becomes compound-specific and to split the mobile phase stream accordingly. These experimental results may be specific to the setup used for this study and may not be directly applicable to other instrument FAIMS devices. 相似文献
143.
Eleven free-base corroles with different electron-donating or electron-withdrawing meso substituents were characterized as to their electrochemistry and UV-visible spectroscopy in benzonitrile (PhCN) or pyridine containing tetra-n-butylammonium perchlorate (0.1 M). Six forms of the compounds with different numbers of protons and/or oxidation states were spectroscopically identified and are represented as (Cor)H3, (.Cor)H2, [(Cor)H2]-, [(.Cor)H2]2-, [(Cor)H4]+, and [(.Cor)H4]2+, where Cor is a trianionic corrole macrocycle. The electrochemistry and UV-visible properties are a function of corrole basicity, solvent basicity, and types or sizes of the meso substituents, and the compounds could be subdivided into one of two different groups, one of which comprises sterically hindered corroles and another that does not. The electroactive species in PhCN is (Cor)H3, whereas in pyridine, one inner proton dissociates, generating a mixture of (Cor)H3, [(Cor)H2]-, and pyH+. The addition of one electron to [(Cor)H2]- reversibly gives the [(.Cor)H2]2- pi-anion radical, whereas a reversible oxidation of the same species gives the neutral radical (.Cor)H2. The first one-electron reduction of (Cor)H3 occurs at the macrocycle in PhCN, but the initial product rapidly converts to [(Cor)H2]-, which undergoes additional reversible redox reactions at the conjugated pi-ring system. The first oxidation of (Cor)H3 in PhCN leads to a mixture of (.Cor)H2 and [(Cor)H4]+, both of which could be further oxidized or reduced. The UV-visible spectra of [(Cor)H4]+ were measured in PhCN after titrations with trifluoroacetic acid, after which selected samples were examined as to their electrochemistry. The HOMO-LUMO gaps of [(Cor)H2]-, (Cor)H3, and [(Cor)H4]+ were also determined. 相似文献
144.
An X-ray fluorescence method (XRF) is presented that allowed low detection limits (at the 0.1–23 ng mL−1 level) to be obtained for Cr, Mn, Fe, Ni, Zn, Sr, Pb, Bi and Br in water. The samples were prepared using a thin layer method. Trace elements were determined via the calibration curve and standard addition. Absorption effects and inhomogenities in prepared samples were checked for using the emission–transmission method and internal standards, respectively. The results from the XRF method were compared with the results from the inductively coupled plasma atomic emission spectrometry method.
相似文献
145.
Godlewska-Zyłkiewicz B 《Analytical and bioanalytical chemistry》2006,384(1):114-123
There are innumerable strains of microbes (bacteria, yeast and fungi) that degrade or transform chemicals and compounds into
simpler, safer or less toxic substances. These bioprocesses have been used for centuries in the treatment of municipal wastes,
in wine, cheese and bread making, and in bioleaching and metal recovery processes. Recent literature shows that microorganisms
can be also used as effective sorbents for solid phase extraction procedures. This review reveals that fundamental nonanalytical
studies on the parameters and conditions of biosorption processes and on metal–biomass interactions often result in efficient
analytical procedures and biotechnological applications. Some selected examples illustrate the latest developments in the
biosorption of metals by microbial biomass, which have opened the door to the application of microorganisms to analyte preconcentration,
matrix separation and speciation analysis. 相似文献
146.
Preparation and characterization of lithium niobate as a novel photocatalyst in hydrogen generation 总被引:2,自引:0,他引:2
Beata Zielińska Ewa Borowiak-Palen Ryszard J. Kalenzuk 《Journal of Physics and Chemistry of Solids》2008,69(1):236-242
Several chemical compounds based lithium niobate have been tested in the reaction for the photocatalytic hydrogen generation. The photocatalysts have been prepared by impregnation of Nb2O5 in the aqueous solution of lithium hydroxide and then the calcination at the temperature range of 400-650 °C. In this report, we present the interesting study showing that the most active catalyst for the photocatalytic generation of hydrogen is the one containing two lithium niobate phases such as LiNbO3 and LiNb3O8. It means that the lithium niobates based catalyst without any further modification or doping can be applied as a novel material for this process. 相似文献
147.
148.
149.
The overall topic of the investigation was the separation of basic proteins by cation exchange displacement chromatography. For this purpose two principal column morphologies were compared for the separation of ribonuclease A and alpha-chymotrypsinogen, two proteins found in the bovine pancreas. These were a column packed with porous particles (Macro-Prep S, 10 microm, 1000 A) and a monolithic column (UNO S1). Both columns are strong cation exchangers, carrying -SO3(-)-groups linked to a hydrophilic polymer support. Poly(diallyl-dimethylammonium chloride) (PDADMAC), a linear cationic polyelectrolyte composed of 100-200 quaternary pyrrolidinium rings, was used as displacer. The steric mass action (SMA) model and, in particular, the operating regime and dynamic affinity plots were used to aid method development. To date the SMA model has been applied primarily to simulate non-linear displacement chromatography of proteins using low molar mass displacers. Here, the model is applied to polyelectrolytes with a molar mass below 20000 g mol(-1), which corresponds to a degree of polymerization below 125 and an average contour length of less than 60 nm. The columns were characterized in terms of the adsorption isotherms (affinity, capacity) of the investigated proteins and the displacer. 相似文献
150.
Joanna?KowalskaEmail author Monika?Asztemborska Beata?Godlewska-?y?kiewicz Jerzy?Golimowski 《Mikrochimica acta》2005,150(1):55-58
The influence of different cleaning procedures applied to quartz vessels used for sample preparation on the Pt contents in blank solutions was studied. The platinum concentration was determined by inductively coupled plasma mass spectrometry. The strong dependence of the memory effect of the quartz crucible on the previously stored Pt content of the sample was observed. It was shown that cleaning a quartz crucible previously used for Pt determinations with hot nitric acid was insufficient. When heating the vessels with a mixture of nitric, perchloric and hydrochloric acid, considerable amounts of Pt are released. In the case of new crucibles, the platinum contents in blanks were very low after cleaning with hot nitric acid. 相似文献