Inverse colloidal crystal membranes for hydrophobic interaction membrane chromatography

A collaborative study on the robustness and portability of a capillary electrophoresis‐mass spectrometry method for peptide mapping was performed by an international team, consisting of 13 independent laboratories from academia and industry. All participants used the same batch of samples, reagents and coated capillaries to run their assays, whereas they utilized the capillary electrophoresis‐mass spectrometry equipment available in their laboratories. The equipment used varied in model, type and instrument manufacturer. Furthermore, different types of sheath‐flow capillary electrophoresis–mass spectrometry interfaces were used. Migration time, peak height and peak area of ten representative target peptides of trypsin‐digested bovine serum albumin were determined by every laboratory on two consecutive days. The data were critically evaluated to identify outliers and final values for means, repeatability (precision within a laboratory) and reproducibility (precision between laboratories) were established. For relative migration time the repeatability was between 0.05 and 0.18% RSD and the reproducibility between 0.14 and 1.3% RSD. For relative peak area repeatability and reproducibility values obtained were 3–12 and 9–29% RSD, respectively. These results demonstrate that capillary electrophoresis‐mass spectrometry is robust enough to allow a method transfer across multiple laboratories and should promote a more widespread use of peptide mapping and other capillary electrophoresis‐mass spectrometry applications in biopharmaceutical analysis and related fields.     

Tetraarylborate polymer networks as single-ion conducting solid electrolytes

A new family of solid polymer electrolytes based upon anionic tetrakis(phenyl)borate tetrahedral nodes and linear bis-alkyne linkers is reported. Sonogashira polymerizations using tetrakis(4-iodophenyl)borate, tetrakis(4-iodo-2,3,5,6-tetrafluorophenyl)borate and tetrakis(4-bromo-2,3,5,6-tetrafluorophenyl)borate delivered highly cross-linked polymer networks with both 1,4-diethynylbeznene and a tri(ethylene glycol) substituted derivative. Promising initial conductivity metrics have been observed, including high room temperature conductivities (up to 2.7 × 10^–4 S cm^–1), moderate activation energies (0.25–0.28 eV), and high lithium ion transport numbers (up to t _Li⁺ = 0.93). Initial investigations into the effects of important materials parameters such as bulk morphology, porosity, fluorination, and other chemical modification, provide starting design parameters for further development of this new class of solid electrolytes.     

Dynamic algorithm selection for pareto optimal set approximation

This paper presents a meta-algorithm for approximating the Pareto optimal set of costly black-box multiobjective optimization problems given a limited number of objective function evaluations. The key idea is to switch among different algorithms during the optimization search based on the predicted performance of each algorithm at the time. Algorithm performance is modeled using a machine learning technique based on the available information. The predicted best algorithm is then selected to run for a limited number of evaluations. The proposed approach is tested on several benchmark problems and the results are compared against those obtained using any one of the candidate algorithms alone.     

Compact poly(ethylene oxide) structures adsorbed at the ethylammonium nitrate-silica interface

The adsorption of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) onto silica from ethylammonium nitrate (a protic ionic liquid) has been investigated using colloid probe AFM force curve measurements. Steric repulsive forces were measured for PEO, confirming that PEO can compete with the ethylammonium cation and adsorb onto silica. The range of the repulsion increases with polymer molecular weight (e.g., from 1.4 nm for 0.01 wt % 10 kDa PEO to 40 nm for 0.01 wt % 300 kDa PEO) and with concentration (e.g., from 16 nm at 0.001 wt % to 78 nm at 0.4 wt % for 300 kDa PEO). Fits to the force curve data could not be obtained using standard models for a polymer brush, but excellent fits were obtained using the mushroom model, suggesting the adsorbed polymer films are compressed and relatively poorly solvated. No evidence for adsorption of 3.5 kDa PPO could be detected up to its solubility limit.     

Fouling behavior of microstructured hollow fiber membranes in dead-end filtrations: critical flux determination and NMR imaging of particle deposition

The fouling behavior of microstructured hollow fibers was investigated in constant flux filtrations of colloidal silica and sodium alginate. It was observed that the fouling resistance increases faster with structured fibers than with round fibers. Reversibility of structured fibers' fouling was similar during silica filtrations and better in sodium alginate filtrations when compared with round fibers. The deposition of two different silica sols on the membranes was observed by NMR imaging. The sols had different particle size and solution ionic strength and showed different deposition behaviors. For the smaller particle-sized sol in deionized solution (Ludox-TMA), there was more deposition within the grooves of the structured fibers and much less on the fins. For the alkali-stabilized sol Bindzil 9950, which had larger particles, the deposition was homogeneous across the surface of the structured fiber, and the thickness of the deposit was similar to that on the round fiber. This difference between the deposition behavior of the two sols is explained by differences in the back diffusion, which creates concentration polarization layers with different resistances. The Ludox sol formed a thick polarization layer with very low resistance. The Bindzil sol formed a slightly thinner polarization layer; however, its resistance was much higher, of similar magnitude as the intrinsic membrane resistance. This high resistance of the polarization layer during the Bindzil sol filtration is considered to lead to quick flow regulation toward equalizing the resistance along the fiber surface. The Ludox particles were trapped at the bottom of the grooves as a result of reduced back diffusion. The fouling behavior in sodium alginate filtrations was explained by considering the size-dependent deposition within the broad alginate size distribution. The better reversibility of fouling in the structured fibers is thought to be the result of a looser deposit within the grooves, which is more easily removed than a compressed deposit on the round fibers.     

A Novel APPI-MS Setup for In Situ Degradation Product Studies of Atmospherically Relevant Compounds: Capillary Atmospheric Pressure Photo Ionization (cAPPI)

We report on the development of a novel atmospheric pressure photoionization setup and its applicability for in situ degradation product studies of atmospherically relevant compounds. A custom miniature spark discharge lamp was embedded into an ion transfer capillary, which separates the atmospheric pressure from the low pressure region in the first differential pumping stage of a conventional atmospheric pressure ionization mass spectrometer. The lamp operates with a continuous argon flow and produces intense light emissions in the VUV. The custom lamp is operated windowless and efficiently illuminates the sample flow through the transfer capillary on an area smaller than 1 mm². Limits of detection in the lower ppbV range, a temporal resolution of milliseconds in the positive as well as the quasi simultaneously operating negative ion mode, and a significant reduction of ion transformation processes render this system applicable to real time studies of rapidly changing chemical systems. The method termed capillary atmospheric pressure photo ionization (cAPPI) is characterized with respect to the lamp emission properties as a function of the operating conditions, temporal response, and its applicability for in situ degradation product studies of atmospherically relevant compounds, respectively.     

Localization of Fatty Acyl and Double Bond Positions in Phosphatidylcholines Using a Dual Stage CID Fragmentation Coupled with Ion Mobility Mass Spectrometry

A high content molecular fragmentation for the analysis of phosphatidylcholines (PC) was achieved utilizing a two-stage [trap (first generation fragmentation) and transfer (second generation fragmentation)] collision-induced dissociation (CID) in combination with travelling-wave ion mobility spectrometry (TWIMS). The novel aspects of this work reside in the fact that a TWIMS arrangement was used to obtain a high level structural information including location of fatty acyl substituents and double bonds for PCs in plasma, and the presence of alkali metal adduct ions such as [M?+?Li]⁺ was not required to obtain double bond positions. Elemental compositions for fragment ions were confirmed by accurate mass measurements. A very specific first generation fragment ion m/z 577 (M-phosphoryl choline) from the PC [16:0/18:1 (9Z)] was produced, which by further CID generated acylium ions containing either the fatty acyl 16:0 (C₁₅H₃₁CO⁺, m/z 239) or 18:1 (9Z) (C₁₇H₃₃CO⁺, m/z 265) substituent. Subsequent water loss from these acylium ions was key in producing hydrocarbon fragment ions mainly from the α-proximal position of the carbonyl group such as the hydrocarbon ion m/z 67 (+H₂C-HC?=?CH-CH?=?CH₂). Formation of these ions was of important significance for determining double bonds in the fatty acyl chains. In addition to this, and with the aid of ¹³C labeled lyso-phosphatidylcholine (LPC) 18:1 (9Z) in the ω-position (methyl) TAP fragmentation produced the ion at m/z 57. And was proven to be derived from the α-proximal (carboxylate) or distant ω-position (methyl) in the LPC.     

Multi-stage solvers optimized for damping and propagation

Explicit multi-stage solvers are routinely used to solve the semi-discretized equations that arise in Computational Fluid Dynamics (CFD) problems. Often they are used in combination with multi-grid methods. In that case, the role of the multi-stage solver is to efficiently reduce the high frequency modes on the current grid and is called a smoother. In the past, when optimizing the coefficients of the scheme, only the damping characteristics of the smoother were taken into account and the interaction with the remainder of the multi-grid cycle was neglected. Recently it had been found that coefficients that result in less damping, but allow for a higher Courant-Friedrichs-Lewy (CFL) number are often superior to schemes that try to optimize damping alone. While this is certainly true for multi-stage schemes used as a stand-alone solver, we investigate in this paper if using higher CFL numbers also yields better results in a multi-grid setting. We compare the results with a previous study we conducted and where a more accurate model of the multi-grid cycle was used to optimize the various parameters of the solver.We show that the use of the more accurate model results in better coefficients and that in a multi-grid setting propagation is of little importance.We also look into the gains to be made when we allow the parameters to be different for the pre- and post-smoother and show that even better coefficients can be found in this way.     

An amino-modified Zr-terephthalate metal-organic framework as an acid-base catalyst for cross-aldol condensation

After controlled pretreatment, some Zr-terephthalate metal-organic frameworks are highly selective catalysts for the cross-aldol condensation between benzaldehyde and heptanal. The proximity of Lewis acid and base sites in the amino-functionalized UiO-66(NH(2)) material further raises the reaction yields.