Taylor dispersion analysis in fused silica capillaries: a tutorial review

Biological and pharmaceutical analytes like liposomes, therapeutic proteins, nanoparticles, and drug-delivery systems are utilized in applications, such as pharmaceutical formulations or biomimetic models, in which controlling their size is often...

White light continuum in negative hollow-core fiber filled with inert gases

As of the writing of this work, generation of white light continuum (WLC) in hollow-core photonic crystal fibers (HCPCF) filled with gases is being thoroughly researched. These structures allow the possibility of adjusting light generation properties by changing the fill gas pressure. Kagomé hollow-core PCF and silica capillaries have been used to study the nonlinear effects in gases as they facilitate exploring these weak properties. In this paper, we numerically analyze the generation of WLC in a new type of hollow-core PCF, called negative curvature hollow-core fiber (NCHCF), itself filled with different inert gases. We show that this type of fiber is a better alternative to the Kagomé and capillary fibers because it exhibits low losses and the WLC spectrum generated presents a relatively flat wavelength span from around 400[Formula: see text]nm to 2400[Formula: see text]nm under certain circumstances.

3D printed droplet generation devices for serial femtosecond crystallography enabled by surface coating

The role of surface wetting properties and their impact on the performance of 3D printed microfluidic droplet generation devices for serial femtosecond crystallography (SFX) are reported. SFX is a novel crystallography method enabling structure determination of proteins at room temperature with atomic resolution using X-ray free-electron lasers (XFELs). In SFX, protein crystals in their mother liquor are delivered and intersected with a pulsed X-ray beam using a liquid jet injector. Owing to the pulsed nature of the X-ray beam, liquid jets tend to waste the vast majority of injected crystals, which this work aims to overcome with the delivery of aqueous protein crystal suspension droplets segmented by an oil phase. For this purpose, 3D printed droplet generators that can be easily customized for a variety of XFEL measurements have been developed. The surface properties, in particular the wetting properties of the resist materials compatible with the employed two-photon printing technology, have so far not been characterized extensively, but are crucial for stable droplet generation. This work investigates experimentally the effectiveness and the long-term stability of three different surface treatments on photoresist films and glass as models for our 3D printed droplet generator and the fused silica capillaries employed in the other fluidic components of an SFX experiment. Finally, the droplet generation performance of an assembly consisting of the 3D printed device and fused silica capillaries is examined. Stable and reproducible droplet generation was achieved with a fluorinated surface coating which also allowed for robust downstream droplet delivery. Experimental XFEL diffraction data of crystals formed from the large membrane protein complex photosystem I demonstrate the full compatibility of the new injection method with very fragile membrane protein crystals and show that successful droplet generation of crystal-laden aqueous droplets intersected by an oil phase correlates with increased crystal hit rates.

Lipophilicity determination of acidic compounds: MEEKC as a reliable high-throughput methodology

In the present study a pressure-assisted MEEKC method with reversed-polarity using a conventional CE instrument with UV detection and uncoated fused silica capillaries is validated as a high-throughput methodology for the lipophilicity determination of the neutral species of acidic compounds (pK_a > 3.5). After the calibration of the system with four standard compounds of known log P_o/w, mass distribution ratios (log k_MEEKC) of new molecules can be directly converted into log P_o/w values by means of a simple linear equation (log P_o/w=a·log k_MEEKC+b). The method was internally and externally validated for a log P_o/w range between -1.54 and 4.75, with higher accuracies than conventional liquid chromatographic methods.

Comparative Enantioseparation of Amlodipine by HPLC and Capillary Electrophoresis

Objective: The purpose of this study was to separate the enantiomers of amlodipine by High Performance Liquid Chromatography (HPLC) using ovomucoid (OVM) as chiral selector, respectively by Capillary Electrophoresis (CE) using cyclodextrines and to evaluate the analytical performance of the both proposed methods.Material and methods: HPLC enantioseparation of amlodipine was performed on an HPLC Agilent Technologies 1100 series using as chiral stationary phase an Ultron ES OVM, 150x4.6 mm column with ovomucoid as chiral selector. The stereoselective CE analysis of amlodipine was achieved on Agilent Technologies 7100 CE using uncoated fused-silica capillaries 48 cm x 50 mm and different type of cyclodextrins as chiral selectors.Results: A mobile phase consisting of 80% Na2HPO4 10 mM at a pH level of 5.0 and 20% ACN, isocratic elution at a flow of 1 ml/min turned to be the optimal experimental conditions for HPLC analysis (R=5.51; α=1.71) with retention times shorter than 10 minutes for the two isomers, tR (S-AML) = 4.63 (min); tR (R-AML) = 5.54 (min). The migration times for amlodipine enantiomers were tm (S-AML) = 8.15 (min) and tm (R-AML)= 8.45 (min) and the optimum CE conditions have proven to be a buffer solution containing 25 mM H3PO4 at pH 3.0 and 20 mM α-CD as chiral selector and a capillary temperature set at 15°C (R=1.51; α=1.03).Conclusion: The analytical performances of the chromatographic method using OVM as chiral selector are superior to the electrophoretic analysis method but the CE method is more economical and may represent an alternative to the HPLC chromatographic separation.

12. Influence of Reaction Conditions on Polymer Morphology in Fused Silica Capillaries

Hydrophobic poly-(benzyl methacrylate-co-1,4 butanediol dimethacrylate) (pBMA) microtubes have been produced through in situ polymerization inside fused silica capillaries. Solvent polarity, reaction temperature and the number of successive polymerization reactions were varied in order to investigate their effect on microtube morphology. It was determined that altering the reaction temperature and solvent polarity enabled control over the degree of tubular morphology, such that the pBMA tubes became more tubular at lower temperatures and in more polar solvents. The thickness of the pBMA tubes increased through multiple successive polymerization reactions. It was determined that pBMA microtube thickness and degree of tubular morphology were controllable, which enables alteration of pBMA tube morphology to optimize their performance in a variety of microscale applications.