Turbulent Supercritical Fluid Chromatography in Open-Tubular Columns for High-Throughput Separations

Emerging Separation Techniques in Supercritical Fluid Chromatography

Supercritical fluid chromatography (SFC) has unique separative characteristics distinguished from those of HPLC and gas chromatography. At present, SFC is widely used and there are many applications in various biological, medical, and pharmaceutical fields. In this review, we focus on recently developed novel techniques related to SFC separation including: new column stationary phases, microfluidics, two-dimensional separation, and gas-liquid separation. In addition, we discuss the application of SFC using a water-containing modifier to biological molecules such as amino acids, peptides, and small proteins that had been challenging analytes.

Rational Strategy for Space-Confined Seeded Growth of ZnO Nanowires in Meter-Long Microtubes

Seeded crystal growths of nanostructures within confined spaces offer an interesting approach to design chemical reaction spaces with tailored inner surface properties. However, such crystal growth within confined spaces tends to be inherently difficult as the length increases as a result of confinement effects. Here, we demonstrate a space-confined seeded growth of ZnO nanowires within meter-long microtubes of 100 μm inner diameter with the aspect ratio of up to 10 000, which had been unattainable to previous methods of seeded crystal growths. ZnO nanowires could be grown via seeded hydrothermal crystal growth for relatively short microtubes below the length of 40 mm, while any ZnO nanostructures were not observable at all for longer microtubes above 60 mm with the aspect ratio of 600. Microstructural and mass spectrometric analysis revealed that a conventional seed layer formation using zinc acetate is unfeasible within the confined space of long microtubes as a result of the formation of detrimental residual Zn complex compounds. To overcome this space-confined issue, a flow-assisted seed layer formation is proposed. This flow-assisted method enables growth of spatially uniform ZnO nanowires via removing residual compounds even for 1 m long microtubes with the aspect ratio of up to 10 000. Finally, the applicably of ZnO-nanowire-decorated long microtubes for liquid-phase separations was demonstrated.

The Application of Covalent Organic Frameworks for Chiral Chemistry

Covalent organic frameworks (COFs) made their debut in 2005 and caused enthusiastic attention because of their ordered, crystalline structure. They are constructed with pure organic building blocks that are linked together by robust covalent linkages. COFs are applied in numerous fields due to their large surface area, architecture and chemistry stabilities, functional pore walls, and tunable frameworks. Incorporating COFs with chiral compounds can build chiral COFs (CCOFs), which have exhibited significant advantages in the chiral chemistry field. This review focuses on the applications of COFs for chiral catalysis, chiral separation, and chiral sensoring up to now. Furthermore, the synthesis and design strategies of CCOFs are also discussed in this article, since the COFs used in chiral chemistry are generally CCOFs. There also sums up the benefits and defects of COFs used in the chiral field and outlines future opportunities. The studies described in this review demonstrate not only the advantages of COFs in practical use but also novel solutions for the problems in the chirality area.