Chromatographic behaviour of synthetic high pressure high temperature diamond in aqueous normal phase chromatography

Effect of ionic liquids as mobile phase additives on retention behaviors of G-quadruplexes in reversed-phase high performance liquid chromatography

G-quadruplexes (G4s) play an important role in a variety of biological processes and have extensive application prospects. Due to the significance of G4s in physiology and biosensing, studies on G4s have attracted much attention, stimulating the development or improvement of methods for G4 structures and polymorphism analysis. In this work, ionic liquids (ILs) were involved as mobile phase additives in reversed-phase high performance liquid chromatography (RP-HPLC) to analyse G4s with various conformations for the first time. How ILs affected the retention behaviors of G4s was investigated comprehensively. It was found that the addition of ILs markedly enhanced G4 retention, along with obvious amelioration on chromatographic peak shapes and separation. The influence of pH of mobile phase and types of ILs were also included in order to acquire an in-depth understanding. It appeared that the effect of ILs on G4 retention behaviors was the result of a combination of various interactions between G4s with the hydrophobic stationary phase and with the IL-containing mobile phase, where ion pair mechanism and enhanced hydrophobic interaction dominated. The findings of this work revealed that ILs could effectively improve the separation of G4s in RP-HPLC, which was conducive to G4 structural analysis, especially for G4s polymorphism elucidation.

Recent advances and applications of synthetic diamonds in solid-phase extraction and high-performance liquid chromatography

Since the advent of diamond-based adsorbents in the late 1960s, the interest in their use for solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) has steadily increased. This is primarily due to their unique properties, such as extreme chemical and thermal stability, high mechanical strength and biocompatibility, and complex mixed-mode retention mechanisms. Currently, the most commonly used synthetic diamonds in SPE and HPLC are detonation nanodiamonds (DND), high-pressure high-temperature (HPHT) diamonds, and chemical vapour deposition (CVD) diamonds. These diamonds have been either used as individual particles (in both modified and unmodified forms), or for surface modification, or entrapped within composites and core-shell particles to develop new diamond-based adsorbents. These diamond-based adsorbents have been used for a variety of applications, including streamlined proteome analysis; extraction of anions, cations, actinides, uranium, lanthanides, alkaline earth metals, transition metals, and post-transition metals; and development of reversed-phase, normal phase, hydrophilic interaction, ion chromatography, and mixed-mode liquid chromatography columns, to name but a few. These varied applications of different types of diamonds are typically governed by their specific properties. This review discusses the various surface and bulk properties of DND, HPHT diamonds, and CVD diamonds that facilitate or limit their use in different SPE and HPLC based applications.