Electroneutral silica-based hybrid monolith for hydrophilic interaction capillary electrochromatography

Preparation and evaluation of highly hydrophilic aptamer-based hybrid affinity monolith for on-column specific discrimination of ochratoxin A

Nonspecific adsorption is a challenge of specific recognition on aptamer-based affinity monoliths. Here, a novel highly hydrophilic polyhedral oligomeric silsesquioxane (POSS)-containing aptamer-based hybrid-silica affinity monolith with a good recognition nature was prepared and used for specific discrimination of ochratoxin A (OTA). A homogeneous polymerization mixture consisted of POSS chemicals, hydrophilic monomers and aptamer solution was directly polymerized via the "one-pot" method. Preparation and characterization of the resultant affinity monolith were studied in detail. A highly hydrophilic nature was obtained and the typical hydrophilic interaction liquid chromatography (HILIC) was observed when acetonitrile (ACN) content in mobile phase was 25%, which reached the highest hydrophilicity of POSS-based hybrid monoliths. By using OTA as model analyte, the nonspecific adsorption was effectively suppressed. The recovery of the analogue ochratoxin B (OTB) was only about 0.1% even if the content of OTB was 50 times more than OTA, which was much better than other POSS-containing monoliths and polar siloxane-based hybrid monoliths. Applied to beer samples, the adsorption of background materials was drastically resisted, and efficient recognition of OTA was obtained with the recoveries of 94.9-99.8%. Much less disturbance was observed than that occurred in hydrophobic POSS-based affinity monolith. It lights an attractive implement with high hydrophilicity and specificity for online selective recognition of OTA.

Advances in hydrophilic nanomaterials for glycoproteomics

Owing to the formidable challenge posed by microheterogeneities in glycosylation sites, macroheterogeneity of the modification number of glycans, and low abundance and ionization efficiency of glycosylation, the crucial premise for conducting in-depth profiling of the glycoproteome is to develop highly efficient technology for separation and enrichment. The appearance of hydrophilic interaction chromatography (HILIC) has considerably accelerated the progress in glycoproteomics. In particular, additional hydrophilic nanomaterials have been developed for glycoproteomics research in the recent years. In this review, we mainly summarize the recent progresses made in the design and synthesis of different hydrophilic nanomaterials, as well as their applications in glycoproteomics, according to the classification of the main hydrophilic functional molecules on the surface. Further, we briefly illustrate the potential retention mechanism of the HILIC mode and discuss the limits and barriers of hydrophilic nanomaterials in glycoproteomics, as well as propose their possible development trends in the future.

One pot synthesis of carboxyl functionalized-polyhedral oligomeric siloxane based monolith via photoinitiated thiol-methacrylate polymerization for nano-hydrophilic interaction chromatography

A hybrid monolith exhibiting almost retention independent separation performance in hydrophilic interaction chromatography (HILIC) was obtained by one-pot photoinitiated thiol-methacrylate polymerization. Polyhedral oligomeric silsesquioxane containing methacrylate units (POSS-MA) was used as the main monomer and crosslinking agent, together with a hydrophilic ligand with two carboxyl groups, mercaptosuccinic acid (MSA) as the thiol agent and chromatographic ligand. The isocratic separation of nucleosides, nucleotides and organic acids on MSA attached-poly(POSS-MA) monolith was investigated in HILIC mode. The van-Deemter plots for obtained for nucleosides, nucleotides and benzoic acids clearly showed that there were two regions in each graph with two different slopes in the studied range of linear flow rate (i.e. 0.2-4.3mm/s). The slope of plate height-linear velocity curve was so small in the low linear velocity region between 0.2-2.1mm/s while the slope in high linear velocity region between 2.1-4.3mm/s was so higher with respect to the first region. The van-Deemter plots sketched for all analyte grous used in HILIC mode obeyed this tendency Almost "retention independent plate height behavior" was demonstrated in HILIC, using nucleotides, nucleotides or benzoic acids as the analytes in the linear velocity range of 0.2-2.1mm/s. This behavior was explained by the porous structure of the synthesized monolith facilitating the convective transport of analytes. The variation of plate height was not retention-independent within high linear velocity range (>3.2mm/s) when nucleosides were separated in HILIC mode.

Preparation of polyhedral oligomeric silsesquioxane based hybrid monoliths by thiol-ene click chemistry for capillary liquid chromatography

A facile organic–silica hybrid monolith was prepared by a thiol-ene click reaction of polyhedral oligomeric silsesquioxane methacryl substituted (POSS-MA) with 1,4-bis(mercaptoacetoxy) butane (BMAB) using toluene and dodecanol as a porogenic system.

Facile one-pot preparation of an imidazolium embedded C8 hybrid monolith using polyhedral oligomeric silsesquioxane for capillary liquid chromatography

In this study, a novel imidazolium embedded C₈ hybrid monolithic column based on polyhedral oligomeric silsesquioxane (POSS) was developed.

Hydrophilic interaction electrokinetic chromatography using bio-based nanofillers

Hydrophilic interaction (HI)-based separation like HILIC is effective for analyzing hydrophilic biological samples such as carbohydrates, peptides, and metabolites. To overcome the drawbacks of conventional HILIC such as large consumption of organic solvents and easy deterioration of the separation column, we developed HI electrokinetic chromatography (EKC) by employing bio-based nanomaterials as the hydrophilic pseudostationary phase. By mechanical/chemical treatments, cellulose, chitin, and chitosan were processed to 10-nm wide nanofibers/nanowhiskers (NFs/NWs), which are longer/shorter than 1000/200 nm, respectively. In HI-EKC of oligosaccharides using 0.001% uncharged cellulose NFs, strong interaction was observed for the large-size oligosaccharides with the retention factors (k) of up to 1.56, indicating a HILIC-mode interaction. In HI-EKC with 0.1% positively charged chitosan NFs, benzenedisulfonic acid, benzenesulfonic acid (BS), and p-hydroxy BS (HBS) had k values of 0.036, 0.018, and 0.018, respectively, suggesting that the ion-exchange interaction mainly occurred via sulfonate groups. Finally, HI-EKC was demonstrated using 0.05% chitin or chitosan NWs. In both cases using chitin and chitosan NWs, HBS showed much stronger interaction with k > 0.192 compared with BS with k < 0.070. It indicated structural difference between NFs and NWs affected the HI behavior in terms of both the ion-exchange and HILIC modes.

Dipyridyl-immobilized ionic liquid type hybrid silica monolith for hydrophilic interaction electrochromatography

A pyridinium-based immobilized ionic liquid type multifunctional hybrid silica monolith was prepared by the in situ polymerization of 3-chloropropyl-silica matrix and 4,4'-dipyridyl for hydrophilic interaction CEC. The obtained hybrid monolith possessed of high stable skeletal microstructures with obviously hydrophilic retention mechanism under ACN content >50% in the mobile phase. Strong and stable anodic EOF could be observed under a broad pH range from pH 3.0 to 9.0. Due to the immobilized dipyridyl groups bonded to the silica matrix surface, the resulting hydrophilic hybrid monolith possessed multiple separation interactions including hydrogen bond, π-π, and anion exchange. Excellent separations of various polar analytes including electroneutral phenols, charged acid nucleotides, and basic analytes were successfully achieved. The highest column efficiencies up to 120,000, 164,000, and 106,000 plates/m were obtained for nucleotides, nucleic acid bases, and nucleosides and nicotines, respectively. These results demonstrated that the dipyridyl-immobilized ionic liquid functionalized hybrid monolith possessed highly mechanical stability and good chromatographic performance for hydrophilic interaction electrochromatography.