ОПРЕДЕЛЕНИЕ АЛЮМИНИЯ В ВОДНЫХ РАСТВОРАХ МЕТОДОМ ИНВЕРСИОННОЙ ВОЛЬТАМПЕРОМЕТРИИ

The possibility for determining the concentration of aluminum in aqueous solutions by stripping voltammetry has been demonstrated. The method is based on electrochemical cathodic aluminum accumulation on a vibrating mercury film electrode with subsequent registration of anodic current on the potentiodynamic voltammogram. Unlike conventional electrochemical methods of indirect determination of aluminum, based on the analysis of the adsorbed complexes of aluminum with dyes, the proposed approach allows to realize the direct determination of aluminum without binding it into coordination compounds. The method is based on the process of reversible reduction and oxidation of aluminum at pH 3,0-4,5 in aqueous dimethyl sulfoxide electrolyte containing calcium chloride, discovered by the authors, and has relative standard deviation of 1,8-2,4% in the aluminum concentration range from 10-4 to 10-5 g/dm3.Показана возможность определения концентрации алюминия в водных растворах методом инверсионной вольт-амперометрии. Метод основан на электрохимическом катодном концентрировании алюминия на вибрирующем ртутном пленочном электроде с последующей регистрацией анодного тока на потенциодинамической вольтампе-рограмме. В отличие от известных электрохимических методик косвенного определения алюминия, основанных на анализе адсорбированных комплексов алюминия с красителями, предложенный подход позволяет осуществлять прямое определение алюминия без связывания его в комплексные соединения. Метод базируется на обнаруженном авторами обратимом процессе восстановления-окисления алюминия при рН 3,0-4,5 в водно-диметилсульфоксидном электролите, содержащем хлорид кальция, и характеризуется относительным стандартным отклонением 1,8-2,4 % в интервале концентраций алюминия от 10-4 до 10-5 г/дм3

The Impact II, a Very High-Resolution Quadrupole Time-of-Flight Instrument (QTOF) for Deep Shotgun Proteomics

Hybrid quadrupole time-of-flight (QTOF) mass spectrometry is one of the two major principles used in proteomics. Although based on simple fundamentals, it has over the last decades greatly evolved in terms of achievable resolution, mass accuracy, and dynamic range. The Bruker impact platform of QTOF instruments takes advantage of these developments and here we develop and evaluate the impact II for shotgun proteomics applications. Adaption of our heated liquid chromatography system achieved very narrow peptide elution peaks. The impact II is equipped with a new collision cell with both axial and radial ion ejection, more than doubling ion extraction at high tandem MS frequencies. The new reflectron and detector improve resolving power compared with the previous model up to 80%, i.e. to 40,000 at m/z 1222. We analyzed the ion current from the inlet capillary and found very high transmission (>80%) up to the collision cell. Simulation and measurement indicated 60% transfer into the flight tube. We adapted MaxQuant for QTOF data, improving absolute average mass deviations to better than 1.45 ppm. More than 4800 proteins can be identified in a single run of HeLa digest in a 90 min gradient. The workflow achieved high technical reproducibility (R2 > 0.99) and accurate fold change determination in spike-in experiments in complex mixtures. Using label-free quantification we rapidly quantified haploid against diploid yeast and characterized overall proteome differences in mouse cell lines originating from different tissues. Finally, after high pH reversed-phase fractionation we identified 9515 proteins in a triplicate measurement of HeLa peptide mixture and 11,257 proteins in single measurements of cerebellum-the highest proteome coverage reported with a QTOF instrument so far

Phosphonic Acid-Functionalized Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly: Synthesis, Characterization, and Occlusion into Calcite Crystals

Dialkylphosphonate-functionalized and phosphonic acid-functionalized macromolecular chain transfer agents (macro-CTAs) were utilized for the reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) at 20% w/w solids in methanol at 64 °C. Spherical, worm-like and vesicular nano-objects could all be generated through systematic variation of the mean degree of polymerization of the core-forming PBzMA block when using relatively short macro-CTAs. Construction of detailed phase diagrams is essential for the reproducible targeting of pure copolymer morphologies, where these were characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS). For nano-objects prepared using the phosphonic acid-based macro-CTA, transfer from methanol dispersion to water leads to the development of anionic surface charge as a result of ionization of the stabilizer chains, but this does not adversely affect the copolymer morphology. Given the well-known strong affinity of phosphonic acid for calcium ions, selected nano-objects were evaluated for their in-situ occlusion within growing CaCO3 crystals. Scanning electron microscopy (SEM) studies provide convincing evidence for the occlusion of both worm-like and vesicular phosphonic acid-based nano-objects and hence the production of a series of interesting new organic-inorganic nanocomposites

Development of an approximate method for quantum optical models and their pseudo-Hermicity

An approximate method is suggested to obtain analytical expressions for the eigenvalues and eigenfunctions of the some quantum optical models. The method is based on the Lie-type transformation of the Hamiltonians. In a particular case it is demonstrated that $E\times \epsilon$ Jahn-Teller Hamiltonian can easily be solved within the framework of the suggested approximation. The method presented here is conceptually simple and can easily be extended to the other quantum optical models. We also show that for a purely imaginary coupling the $E\times \epsilon$ Hamiltonian becomes non-Hermitian but $P\sigma _{0}$-symmetric. Possible generalization of this approach is outlined.Comment: Paper prepared fo the "3rd International Workshop on Pseudo-Hermitian Hamiltonians in Quantum Physics" June 2005 Istanbul. To be published in Czechoslovak Journal of Physic

Droplet Microfluidics XRD Identifies Effective Nucleating Agents for Calcium Carbonate

The ability to control crystallization reactions is required in a vast range of processes including the production of functional inorganic materials and pharmaceuticals and the prevention of scale. However, it is currently limited by a lack of understanding of the mechanisms underlying crystal nucleation and growth. To address this challenge, it is necessary to carry out crystallization reactions in well‐defined environments, and ideally to perform in situ measurements. Here, a versatile microfluidic synchrotron‐based technique is presented to meet these demands. Droplet microfluidic‐coupled X‐ray diffraction (DMC‐XRD) enables the collection of time‐resolved, serial diffraction patterns from a stream of flowing droplets containing growing crystals. The droplets offer reproducible reaction environments, and radiation damage is effectively eliminated by the short residence time of each droplet in the beam. DMC‐XRD is then used to identify effective particulate nucleating agents for calcium carbonate and to study their influence on the crystallization pathway. Bioactive glasses and a model material for mineral dust are shown to significantly lower the induction time, highlighting the importance of both surface chemistry and topography on the nucleating efficiency of a surface. This technology is also extremely versatile, and could be used to study dynamic reactions with a wide range of synchrotron‐based techniques