Catalyst assisted synthesis of initiator attached silica monolith particles via isocyanate-hydroxyl reaction for production of polystyrene bound chromatographic stationary phase of excellent separation efficiency

Preparation of mixed-mode stationary phase for separation of peptides and proteins in high performance liquid chromatography

Porous silica particles were prepared by sol–gel method with some modification to get wide-pore particles. These particles were derivatized with N-phenylmaleimide-methylvinylisocyanate (PMI) and styrene by reversible addition fragmentation chain transfer (RAFT) polymerization to prepare N-phenylmaleimide embedded polystyrene (PMP) stationary phases. Narrow bore stainless steel column (100 × 1.8 mm i.d) was packed by slurry packing method. The chromatographic performance of PMP column was evaluated for the separation of synthetic peptides mixture composed of five peptides (Gly-Tyr, Gly-Leu-Tyr, Gly-Gly-Tyr-Arg, Tyr-Ile-Gly-Ser-Arg, Leucine enkephalin) and tryptic digest of human serum albumin (HAS) respectively. Number of theoretical plates as high as 280,000 plates/m were obtained for peptides mixture at optimum elution condition. Separation performance of the developed column was compared with commercial Ascentis Express RP-Amide column and it was observed that separation performance of PMP column was better than commercial column in terms of separation efficiency and resolution.

Fast liquid chromatography method for separation of peptides using a sub-2 μm ground silica monolith packed column

A stationary phase based on sub-2 μm ground silica monolith particles was fabricated by in situ polymerization and applied in micro-column for separation of peptides. The sub-2 μm silica particles were obtained from monolith using sol-gel process followed by grinding and sedimentation to remove the fines. Initially, the silica monolith particles were pretreated with 3-trimethoxysilyl propyl methacrylate to attach double-bonded ligands onto the surface, then a network structure was formed onto the surface of the particle using styrene, N-isopropylacrylamide, and ethylene glycoldimethacrylate. The effect of the flow rate of the mobile phase on the separation performance was investigated. The stationary phase was characterized by field emission scanning electron microscopy, thermogravimetry, particle size distribution, and element analysis. The resultant phase was packed in glass-lined stainless steel micro-columns (2.1 mm × 50 mm) and evaluated for fast separation. An average number of theoretical plates as high as 9800 plates/column (5.10 μm plate height) was achieved for five synthetic peptides under the optimized flow rate of 0.15 mL/min. The repeatabilities of column-to-column, intraday, and interday through relative standard deviation were found better than 4%, exhibiting satisfactory repeatability of the developed micro-column for fast separation of peptides.

Mixed-mode open tubular column for peptide separations by capillary electrochromatography

Mixed-mode chromatography open tubular column has been developed for peptide separation in electrochromatography. A column with 92 cm effective length and 50 μm internal diameter is fabricated internally with a copolymer sheet of restricted thickness. Catalyst facilitated binding of the coupling agent 3,5-bis (trifluoromethyl) phenyl isocyanate has been carried out at the interior surface of the column. The initiator sodium diethyldithiocarbamate was bound to the coupling agent. A small amount of N-[2-(acryloylamino) phenyl] acrylamide was used along with methacrylic acid and styrene in the monomer mixture to induce a little polar character in the stationary phase fabricated inside the column. Twenty-three peptides have been separated from a chemically digested protein mixture present in cytochrome C in capillary electrochromatography, in addition to the separation of six commercial peptides. We achieved an average plate count of over 1.5 million/m with the column of current study both for the digested protein components and commercial peptides using 70/30% v/v (acetonitrile/20 mM ammonium formate) at pH 6.5. In addition, the column resulted in baseline separation of all the peptides with very good resolution, enhanced peak capacity, and better retention time span.

Polystyrene Immobilized Sol-Gel Ground Silica Monolith Particles Using One-Pot Reaction of Enhanced Separation Efficiency

The stationary phase based on sol-gel ground silica monolith particles has been produced by one-pot polymerization method incorporation of styrene and ethylene dimethacrylate. First, the ground silica monolith particles were prepared by a sol-gel process followed by sedimentation. The particles were then subjected to modify with styrene ligand via one-pot polymerization, whereas ethylene dimethacrylate was used as the cross-linker. The glass lined stainless steel columns (1 mm internal diameter, 150 mm length) were packed with the above phase for estimation of the chromatographic performance in high-performance liquid chromatography. An average number of theoretical plates of as high as 39,300 plates/column was obtained under the optimized elution condition. The column-to-column reproducibility was proved satisfactory in separation efficiency and retention factor. The experimental results indicate that sol-gel ground silica particles prepared by an aid of one-pot modification can provide a better way for preparation of highly efficient stationary phase.

Particle packed mixed-mode chromatographic stationary phase for the separation of peptide in liquid chromatography

A particle-based stationary phase has been prepared for the separation of five synthetic peptides and a mixture containing tryptic digest of cytochrome C in liquid chromatography. Particles originating from silica monolith were differentially sedimented to obtain 1-2 μm particles. A stationary phase was achieved by the coating of poly(styrene-methacrylic acid-N-phenylacrylamide) copolymer onto the particles via reversible addition-fragmentation chain transfer polymerization reaction. Stainless steel column (30 cm long and 1 mm internal diameter) was packed with stationary phase. Very high separation efficiency (ca. 351 000 plates/m) was achieved for five commercial peptides with a percent relative standard deviation of less than 1%. Protocol for the synthesis and modification of silica monolith particles has been well optimized with a good reproducibility both in particle and pore size. The column resolved about 21 peptide components from a mixture containing tryptic digest of cytochrome C, under the elution conditions of acetonitrile/15 mM ammonium format (65/35 v/v%) with a flow rate of 28 μL/min.

Hydroxypropyl-β-cyclodextrin encapsulated stationary phase based on silica monolith particles for enantioseparation in liquid chromatography

Hydroxypropyl-β-cyclodextrin-encapsulated stationary phase incorporated on silica monolith particles was prepared by physical embedding, providing a new method for the development of chiral stationary phase for enantioseparation in liquid chromatography. Ground silica monolith particles of about 2.0 μm were prepared via sol-gel reaction followed by differential sedimentation. Initially, the silica monolith particles were pretreated with 3-trimethoxysilyl propyl methacrylate to attach double-bonded ligands onto the surface, then a network structure was formed onto the surface of the particle using N-isopropyl acrylamide as functional monomer. Hydroxypropyl-β-cyclodextrin was encapsulated inside N-isopropyl acrylamide copolymerized layer on the surface of silica monolith particles. The effect of the amount of chiral selector on the chromatographic efficiency of the chiral stationary phase was examined. The glass lined stainless steel columns (1 mm internal diameter, 300 mm length) were packed with the stationary phase for estimation of the efficiency by separation of phenylsuccinic acid, oxybutynin, equol, and naproxen enantiomers in high-performance liquid chromatography, with the resolutions of 1.54, 1.72, 2.54, and 2.31, respectively. The column to column repeatabilities through relative standard deviation were found better than 3%. The experimental results indicate that the sol-gel ground silica particles modified with β-cyclodextrin provide a promising way for the separation of chiral enantiomers.