An in situ growth approach to the fabrication of zeolite imidazolate framework-90 bonded capillary column for gas chromatography separation

Preparation of UiO-66 MOF-Bonded Porous-Layer Open-Tubular Columns Using an In Situ Growth Approach for Gas Chromatography

The thermally stable zirconium-based MOF, UiO-66, was employed for the preparation of bonded porous-layer open-tubular (PLOT) GC columns. The synthesis included the in situ growth of the UiO-66 film on the inner wall of the capillary through a one-step solvothermal procedure. SEM-EDX analysis revealed the formation of a thin, continuous, uniform, and compact layer of UiO-66 polycrystals on the functionalized inner wall of the column. The average polarity (ΔIav = 700) and the McReynolds constants reflected the polar nature of the UiO-66 stationary phase. Several mixtures of small organic compounds and real samples were used to evaluate the separation performance of the fabricated columns. Linear alkanes from n-pentane to n-decane were baseline separated within 1.35 min. Also, a series of six n-alkylbenzenes (C3-C8) were separated within 3 min with a minimum resolution of 3.09, whereas monohalobenzene mixtures were separated at 220 °C within 14s. UiO-66 PLOT columns are ideally suited for the isothermal separation of chlorobenzene structural isomers at 210 °C within 45 s with Rs ≥ 1.37. The prepared column featured outstanding thermal stability (up to 450 °C) without any observed bleeding or significant impact on its performance. This feature enabled the analysis of various petroleum-based samples.

A stamped aluminium gas chromatographic column disk employing directly grown anodic aluminium oxide stationary phase for the separation of aromatic and chlorinated compounds

In this study, mesoporous anodic aluminium oxide (AAO) with moderate polarity was used as a GC stationary phase to demonstrate the applicability to various compound species. The fluidic channel measured 6 meters in length and had a cross-section area of 0.127 mm2. The column disk measured 6.2 cm in diameter and was fabricated through a stamping process on an aluminium substrate. The AAO stationary phase was directly grown on the aluminium substrate through an anodization process using oxalic acid as the electrolyte. The pore size of the AAO stationary phase was approximately 50-70 nm, with film thicknesses ranging from 6-20 μm. AAO based on oxalic acid exhibited significantly reduced surface polarity, making it suitable for separating polarizable and slightly polar compounds. The theoretical plate number for benzene had reached 1800 plates per meter, and for n-butane, it had reached 2500 plates per meter. A complex mixture of 16 compounds spanning alkanes, olefins, aromatics, and chlorinated hydrocarbons was effectively separated in 8 minutes with the temperature programmed to 200 °C.

Trends in monoliths: Packings, stationary phases and nanoparticles

Monoliths media are gaining interest as excellent substitutes to conventional particle-packed columns. Monolithic columns show higher permeability and lower flow resistance than conventional liquid chromatography columns, providing high-throughput performance, resolution and separation in short run times. Monolithic columns with longer length, smaller inner diameter and specific selectivity to peptides or enantiomers have been played important role in hyphenated system. Monolithic stationary phases possess great efficiency, resolution, selectivity and sensitivity in the separation of complex biological samples, such as the complex mixtures of peptides for proteome analysis. The development of monolithic stationary phases has opened the new avenue in chromatographic separation science and is in turn playing much more important roles in the wide application area. Monolithic stationary phases have been widely used in fast and high efficiency one- and multi-dimensional separation systems, miniaturized devices, and hyphenated system coupled with mass spectrometers. The developing technology for preparation of monolithic stationary phases is revolutionizing the column technology for the separation of complex biological samples. These techniques using porous monoliths offer several advantages, including miniaturization and on-line coupling with analytical instruments. Additionally, monoliths are ideal support media for imprinting template-specific sites, resulting in the so-called molecularly-imprinted monoliths, with ultra-high selectivity. In this review, the origin of the concept, the differences between their characteristics and those of traditional packings, their advantages and drawbacks, theory of separations, the methods for the monoliths preparation of different forms, nanoparticle monoliths and metal-organic framework are discussed. Two application areas of monolithic metal-organic framework and nanoparticle monoliths are provided. The review article discusses the results reported in a total of 218 references. Other older references were included to illustrate the historical development of monoliths, both in preparation and types, as well as separation mechanism.

Linker Scissoring Strategy Enables Precise Shaping of Metal-Organic Frameworks for Chromatographic Separation

Precise shaping of metal-organic frameworks (MOFs) is significant in both fundamental coordination chemistry and practical applications, such as catalysis, separation, and biomedicine. Herein, we demonstrated a linker scissoring strategy for precisely shaping MOFs through surface conformational pairing. In this strategy, the bidentate linkers which were designed according to the original tetratopic ligands and the coordination environment of MOF surfaces, were utilized as the covering agents. The shape of these covering agents and the surface conformation of metals onto MOFs restricted them to coordinate on specific MOF facets thus precisely controlling the shape of the MOFs. Different shapes of PCN-608 from nanoplate (PCN-NP) to nanorod (PCN-NR) have been targeted by adding different bidentate linkers. The universality of this strategy was demonstrated by controlling the shapes of the NU-MOFs from nanoplate to nanorod. This strategy provides a new guiding principle to synthesize MOF nanocrystals with controlled shapes.

A novel column fabrication approach for capillary gas chromatography via a cross-linked organogel network with high stability and inertness

A new column fabrication approach for capillary gas chromatography with high column selectivity, stability and inertness.

An alternative approach for the preparation of a core–shell bimetallic central metal–organic framework as a hydrophilic interaction liquid chromatography stationary phase

A new type of core–shell composite material was prepared and applied as a hydrophilic interaction liquid chromatography (HILIC) stationary phase.

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry

Porous organic frameworks (POFs), a general term for covalent-organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state-of-the-art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in "turn-off" or "turn-on" fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.

Recent advances in metal-organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.

Molecularly imprinted plasmonic nanosensor for selective SERS detection of protein biomarkers

Molecularly imprinted plasmonic nanosensor has been prepared via the rational design of an ultrathin polymer layer on the surface of gold nanorods imprinted with the target protein. This nanosensor enabled selective fishing-out of the target protein biomarker even from a complex real sample such as human serum. Sensitive SERS detection of the protein biomarkers with a strong Raman enhancement was achieved by formation of protein imprinted gold nanorods aggregates, stacking of protein imprinted gold nanorods onto a glass plate, or self-assembly of protein imprinted gold nanorods into close-packed array. High specificity and sensitivity of this method were demonstrated with a detection limit of at least 10(-8)mol/L for the target protein. This could provide a promising alternative for the currently used immunoassays and fluorescence detection, and offer an ultrasensitive, non-destructive, and label-free technique for clinical diagnosis applications.

In situ hydrothermal growth of a dual-ligand metal–organic framework film on a stainless steel fiber for solid-phase microextraction of polycyclic aromatic hydrocarbons in environmental water samples

In situ hydrothermal growth of bio-MOF-1 film on stainless steel fiber for solid-phase microextraction of polycyclic aromatic hydrocarbons.