Cross-linked polysiloxane-coated stable bond O-9-(2,6-diisopropylphenylcarbamoyl)quinine and quinidine chiral stationary phases as well as application in enantioselective cryo-HPLC.

In this work, brush-type chiral stationary phases (CSPs) with O-9-(2,6-diisopropylphenylcarbamoyl)-modified quinidine (DIPPCQD-brush/-SH) and O-9-(2,6-diisopropylphenylcarbamoyl)-modified quinine (DIPPCQN-brush/-SH) were prepared as benchmarks for comparison with new corresponding polymeric CSPs with more stable bonding chemistry. These polymeric CSPs were prepared by coating a thin poly(3-mercaptopropyl)-methylsiloxane film together with the chiral selector onto vinyl-modified silica. In a second step, immobilization of the quinine/quinidine derivatives as well as cross-linking of the polysiloxane film to the vinyl-silica is achieved by a double thiol-ene click reaction.

Preparation and characterization of poly(3-mercaptopropyl)methylsiloxane functionalized silica particles and their further modification for silver ion chromatography and enantioselective high-performance liquid chromatography.

The present work reports on the preparation of polythiol-functionalized silica particles by thermally and photo-initiated radical addition reactions using poly(3-mercaptopropyl)methylsiloxane (PMPMS) as sulfhydryl group-rich surface modification reagent. Prior to surface modification with PMPMS, the silica was vinylized with vinyl trimethoxysilane. Finally, the usefulness of the thiolated silica particles was demonstrated by their further modification for various HPLC applications such as argentation chromatography and chiral separations.

Evaluation of superficially porous particle based zwitterionic chiral ion exchangers against fully porous particle benchmarks for enantioselective ultra-high performance liquid chromatography.

Zwitterionic chiral ion-exchange selectors (ZWIX) obtained by conjugation of quinine and 2-aminocyclohexanesulfonic acid via a carbamate bond were immobilized on three different silica particle types, viz. 120 Å 3 μm fully porous particles (FPP), 200 Å 3 μm FPP and 160 Å 2.7 μm superficially porous particles (SPP).

Stable-bond polymeric reversed-phase/weak anion-exchange mixed-mode stationary phases obtained by simultaneous functionalization and crosslinking of a poly(3-mercaptopropyl)methylsiloxane-film on vinyl silica via thiol-ene double click reaction.

A polymeric reversed-phase/weak anion exchange (Poly-RP/WAX) mixed-mode stationary phase has been prepared by coating of a poly(3-mercaptopropyl)methylsiloxane film on vinyl-modified silica (100 Å, 5 μm) and simultaneous in situ functionalization with N-(10-undecenoyl)-3-aminoquinuclidine as well as crosslinking to the vinyl silica surface by solventless thiol-ene double click reaction. Such bonding chemistry showed greatly enhanced stability compared to brush-type analogs with bifunctional siloxane bonding to silica. Solid-state Si-CP/MAS NMR confirmed the immobilization of the siloxane layer.

Comparison of small size fully porous particles and superficially porous particles of chiral anion-exchange type stationary phases in ultra-high performance liquid chromatography: effect of particle and pore size on chromatographic efficiency and kinetic performance.

Recent advancements in particle design are common in reversed-phase liquid chromatography (RPLC), but in chiral separations their use is still sporadic in commercially available chiral stationary phases (CSPs). Due to reported lower mass transfer resistance, they might be a promising opportunity to increase efficiency and reduce time of analysis since the relatively higher mass transfer resistance term of CSPs caused by slow adsorption-desorption kinetics is the most performance-limiting factor in enantioselective chromatography. This study was dedicated to the evaluation of new support materials for tert-butylcarbamoylquinine (tBuCQN) based CSP to provide highly efficient and fast enantioseparations.

Zwitterionic codeine-derived methacrylate monoliths for enantioselective capillary electrochromatography of chiral acids and chiral bases.

Thiol-ene click reaction of N-acetyl-L-cysteine methyl ester to codeine, followed by reaction with allyl isocyanate and hydrolysis to the corresponding zwitterionic chiral selector and its subsequent bonding to the surface of a methacrylate monolith provided a new chiral capillary column for enantiomer separation of chiral acids and chiral bases. First, the epoxy groups of a poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith were converted into amine residues, followed by reaction with allylglycidyl ether. In this way, a spacer arm was bonded to the surface before coating and cross-linking poly(3-mercaptopropyl methylsiloxane) (PMPMS) via radical addition (thiol-ene click reaction) to the surface.

Imaging Peptide and Protein Chirality via Amino Acid Analysis by Chiral × Chiral Two-Dimensional Correlation Liquid Chromatography.

The present contribution illustrates the utilization of a chiral × chiral two-dimensional liquid chromatography (2DLC) setup with tert-butylcarbamoyl quinine chiral stationary phase (CSP) in the first dimension (D) and tert-butylcarbamoyl quinidine CSP in the second dimension (D) to analyze FMOC-derivatized d and l amino acids from peptide hydrolysates. Hereby, in the D and D chiral separation dimensions factors such as selector and immobilization chemistry of the CSPs, mobile phase, temperature, column hardware dimensions, stationary phase supports, particle type and packing were identical. Orthogonality between D and D CSPs was solely based on their stereochemistry, i.

Enantioselective multiple heartcut two-dimensional ultra-high-performance liquid chromatography method with a Coreshell chiral stationary phase in the second dimension for analysis of all proteinogenic amino acids in a single run.

A multiple heartcut (MHC) 2D-UHPLC method with UV detection has been developed for the enantioselective analysis of complex amino acid mixtures in a single run. The MHC method is based on an achiral gradient RPLC separation with 1.8 μm C18 phase (100 × 2.

Complementary enantioselectivity profiles of chiral cinchonan carbamate selectors with distinct carbamate residues and their implementation in enantioselective two-dimensional high-performance liquid chromatography of amino acids.

A cardinal requirement for effective 2D-HPLC separations is sufficient complementarity in the retention profiles of first and second dimension separations. It is shown that retention and enantioselectivity of chiral selectors derived from cinchona alkaloids can be conveniently modulated by structural variation of the carbamate residue of the quinine/quinidine carbamate ligand of such chiral stationary phases (CSP). A variety of aliphatic and aromatic residues have been tested in comparison to non-carbamoylated quinine CSP.

Surface-anchored counterions on weak chiral anion-exchangers accelerate separations and improve their compatibility for mass-spectrometry-hyphenation.

In the present work we propose new variants of chiral stationary phases (CSP) with tert-butylcarbamoylquinine (tBuCQN) as chiral selector molecule. Four tBuCQN-CSPs with distinct bonding chemistries are compared in terms of their pH-dependent surface charge by ζ-potential determinations, by achiral and chiral liquid chromatographic tests and LC-ESI-MS hyphenation. In one embodiment tBuCQN was immobilized on 3-mercaptopropylmethylsilyl-modified silica by thiol-ene click reaction (brush type CSP with selector coverage of 0.

Preparation of fluorescent labeled gentamicin as biological tracer and its characterization by liquid chromatography and high resolution mass spectrometry.

This work deals with the preparation of single-labeled bioconjugates of the antibiotic Gentamicin (GT) with the sulforhodamine-derived fluorescence dye Texas Red(®)-X (TR), its purification by high-performance liquid chromatography (HPLC) and its characterization by high-resolution mass spectrometry. Aminoglycosides such as GT are efficient antibiotics, but also problematic due to severe side effects such as nephro- and ototoxicity. Fluorescent labeled GT is used to visualize cellular uptake and distribution of the antibiotic to finally understand the mechanisms of serious adverse drug reactions.