TY - JOUR
AU - Lu, Yao
AB - Abstract 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. Introduction High-performance liquid chromatography (HPLC) is a chromatographic technique in analytical chemistry used to separate, identify and quantify each component in complex mixtures (1–3). During the past decade, HPLC column techniques have been advancing continuously and substantial improvements have been achieved in the development of reversed-phase HPLC packaging materials (4, 5). Traditional packed columns have gone through a long and tedious process of optimization and improvement to address the increasing challenges of purification and separation due to the rapid development of natural, pharmaceutical and clinical sciences (6–10). High efficiency and high-speed separations in HPLC have been studied by using small particles. As indicated, the reduction in particle size leads directly to higher column efficiency, or reduced plate height, in the high linear velocity region (11). However, columns packed with 5 μm particles are still most widely used, whereas 1–3 μm particles are used in short columns due to the high back pressure associated with such small particles. However, by decreasing the size of particles, the practical disadvantages stem from the excessive operational pressure drop needed to force mobile phase through the column and the difficulty of preparing a uniform packing of extremely fine materials. Intensive research has been carried out in several areas to overcome these troubles (12, 13), that is, so-called ultrahigh-pressure liquid chromatography (14, 15) and capillary electrochromatography (16, 17). The modern advanced pumps capable of delivering system pressures up to 1,000 bar are commercially available and employed for columns packed with sub-2 μm or even smaller particles (18, 19). The stationary phases based on ground silica monolith particles may be adopted to solve the column packing difficulties. Such stationary phases have been developed in many laboratories (20–26). Their unique character of ground particles brings up a partially monolithic structure in the resultant bed, providing rapid slurry flux during packing to give better packing quality than the case where spherical particles are packed. Higher separation efficiency (up to 195,000 plates/m) and better permeability (2.4 × 10−14 m2 for 3.9 μm C18-modified silica monolith particles) have been obtained with ligand-modified silica monolith particles than spherical porous silica particles. Their separation efficiencies can be well compared with those of core-shell particles of similar average particle sizes, whereas the resultant column back pressure is lower than that of conventional spherical particles (27, 28). Those stationary phases were mostly C18 and polystyrene ligand-modified silica monolith particles. The stationary phases of silica particles derivatized with proper alkyl chains are still by far the most widely employed products for reversed-phase HPLC columns. Polymer layer may be bound to the support surface of silica particles. The “grifting form” polymerization is better than the conventional free radical polymerization in the viewpoint of separation efficiency of the resultant phases. In conventional radical polymerization, it is difficult to control the rate of chain propagation, and generated polymers generally show a wide size distribution due to side reactions, including chain transfer and termination (29). In this work, one-pot reaction approach was adapted to form polymer layer to the support surface of materials. The column packing procedure has a vast effect on chromatographic performance (30). The operational parameters of column packing should be optimized to make durable, highly efficient and reproducible HPLC columns. The structure of the packed bed greatly affects the HETP in relation to the radial heterogeneity of packed bed (31). The change of stationary phase structure across the column diameter occurs at different slurry concentration, different packing rate and different aspect ratio (32). The low viscosity slurry method was identified as superior over high-density techniques for packing silica monolith particles. The constant packing pressure was favored over the constant flow rate version. It was also demonstrated that thin screens located at column inlets and outlets for capturing the stationary phase particles produced the better column efficiency than other capturing units (33). In this work, a three-stage sedimentation process was incorporated in the manufacturing of ground silica monolith particles to further enhance the particle size distribution (PSD). The ground silica monolith particles were then chemically modified with polystyrene ligand via one-pot polymerization, whereas ethylene dimethacrylate (EDMA) was used as the cross-linker. Five test compounds (phenol, acetophenone, 4-methyl-2-nitroaniline, benzene and toluene) were separated with the column packed with optimized stationary phase, and the average number of theoretical plates over five analytes was 39,300. Experimental Materials Polyethylene glycol (PEG), trimethylorthosilicate (TMOS), urea, acetic acid, phenol, acetophenone, 4-methyl-2-nitroaniline, benzene, toluene, 3-(methacryloxy)propyltrimethoxysilane (r-MAPS), EDMA, azodiisobutyronitrile (AIBN) and styrene were purchased from Sigma-Aldrich (St. Louis, MO, USA). HPLC-grade acetonitrile (ACN), methanol, 2-propanol, acetone and water were purchased from Mallinckrodt Baker (Phillipsburg, NJ, USA) and utilized without purification. Screen frits (1.0 μm pore size) were purchased from Valco (Houston, TX, USA) and glass-lined stainless steel tubing (30 cm, 1.0 mm I.D., 1/8 inch O.D.) and Teflon sleeves were purchased from Grace (Deerfield, IL, USA). Synthesis of ground silica monolith particles PEG 18 g and urea 20 g were dissolved in 0.01 M acetic acid (180 mL), and 60 mL TMOS was added slowly in a Teflon vial, and the mixture was stirred for 60 min under ice bath condition, then the Teflon vial was heated at 40°C for 24 h in an oven and at 120°C in an autoclave for 24 h. The Teflon container was removed from the autoclave, and the aqueous liquid was decanted off. The soft silica monolith was dried at 70°C for 24 h, smoothly ground with mortar and pestle, and calcined at 550°C for 12 h in a muffle furnace. The ground silica monolith particles of a total mass of 20 g were obtained. Three-stage sedimentation The calcined silica monolith particles (20 g) were suspended in 2.0 L methanol by vigorous stirring for overnight in a beaker and transferred to a plastic-made Imhoff sedimentation cone (Figure 1). The particles were left alone to settle by gravity for 5 h. Two zones of the same height were divided in the cone. The heavier particles settled down quickly to the bottom section and the lighter particles stayed in the top section. Both sections were separately collected by vacuum suction and filtered. The particles of only the bottom section were subjected to the second and third sedimentation in just the same way as in the first sedimentation. The bottom section of the last sedimentation was filtered and dried in an oven at 120°C for overnight. The recovery of this section was ca 60% (12 g). The ground silica monolith particles were then taken for scanning electron microscopic (SEM) pictures. Figure 1 Open in new tabDownload slide The sedimentation cone showing the up and down sections in which silica monolith particles are differentially sedimented according to their sizes. Figure 1 Open in new tabDownload slide The sedimentation cone showing the up and down sections in which silica monolith particles are differentially sedimented according to their sizes. Synthesis of polystyrene-bound stationary phase A total of 2 g ground silica monolith particles were dried at 120°C for 12 h in a vacuum oven. For the pretreatment of the ground silica monolith particles, the above dried silica monolith particles were suspended into the solution of γ-MAPS (3 mL) and methanol (27 mL) with ultrasound sonication for 20 min. The reaction mixture was reacted at 60°C for overnight with stirring to vinylized the surface of silica particles. Sequentially, the product was flushed with methanol to remove the residuals and then dried at 60°C with a flow of nitrogen for further use. As illustrated in Figure 2, the one-pot polymerization was employed for the preparation of the stationary phase for column. The polymerization solution was prepared using the following procedures: (1) styrene (2 mL), ACN (20 mL), 2-propanol (10 mL) and pretreated dried ground silica monolith particles were accurately weighted; (2) cross-linker reagent EDMA (1 mL) and AIBN as the initiator (0.2 g) were added into the same reactor; and (3) the resulting mixture was sonicated at room temperature for 15 min and then purged with nitrogen for 10 min to remove the bubbles. Subsequently, the polymerization mixture was reacted at 70°C for 10 h with constantly stirring. The resulting phase was washed to remove the residual reagents dried under a nitrogen atmosphere. Figure 2 Open in new tabDownload slide Reaction scheme of one-pot polymerization on silica monolith particles. Figure 2 Open in new tabDownload slide Reaction scheme of one-pot polymerization on silica monolith particles. Characterization The prepared stationary phase was characterized by particles size distribution (PSD), field-emission scanning electron microscopy (FE-SEM), elemental analysis and nitrogen adsorption/desorption analysis. The SEM images were carried on S4800 FE-SEM (Hitachi, Japan). The PSD data was obtained from Mastersizer 2000 particle size analyzer (Worcestershire, UK). The elemental analysis data was carried on Thermo Electron Flash EA1112 elemental analyzer (Waltham, MA, USA). The nitrogen adsorption/desorption isotherms, Barrett–Joyner–Halenda (BJH) adsorption pore sizes and Brunauer–Emmett–Teller (BET)-specific surface areas of bare particles and copolymer-stationary phase were obtained by a BEL-Japan BELSORP-Max (Osaka, Japan). The samples were degassed at 373 K for 10 h under the vacuum up to 10−3 Torr. The total pore volume was determined by the amount of N2 adsorbed at a relative pressure of P/Po = 0.99. HPLC The HPLC system was homebuilt by assembling a 10 AD pump (Schimadzu, Tokyo Japan), a Valco (Houston, TX, USA) C14W.05 injector with 50 nL injection loop and a Jasco (Tokyo, Japan) UV-2075 capillary window detector. The software Multichro 2000 from Yullin Technology (Seoul, Korea) was used for acquisition and processing of chromatographic data. A commercial screen frit (1.0 μm pore) was placed in a reducing union (1/8–1/16 inch) and a glass-lined stainless steel column (1.0 × 150 mm) was fitted to the union, and the other end of column was connected to the packer slurry reservoir. A slurry (concentration 0.1 g/mL) was prepared by suspending 120 mg chiral stationary phase in 1.2 mL methanol and treated with ultrasound sonication for 20 min (30). The pressure sequence employed for the 150 mm length column was as follows: 1,000 bar for 5 min with vibration, 800 bar for 10 min with vibration and 600 bar for 30 min without vibration. The column after packing was connected to the HPLC system and the mobile phase was 60/40 (v/v) ACN/water with 0.1% TFA. The KNO3 was used to determine the column void volume. Results Three-stage sedimentation of ground silica monolith particles Very tiny fines were initially included in the product of ground silica monolith particles causing serious problems such as development of high back pressure, poor column packing quality and frit clogging. In order to remove such fines, 20 g silica monolith particles are vigorously dispersed in 2 L methanol for overnight and introduced into the sedimentation cone. As the heavier particles settled into the bottom section, the lighter particles (fine particles) were suspended in the upper portion of the cone. The particles of each section were collected. The bottom section was used for second and third sedimentation to completely remove the fines. The polystyrene modification of the above silica monolith particles resulted in a stationary phase of enhanced separation efficiency, as demonstrated in the following sections. Morphology of the stationary phase The SEM images of bare and polystyrene-modified particles are shown in Figure 3. The SEM photographs were taken to confirm the presence of a cross-linked network layer on the silica support. Figure 3 revealed a clear change of surface morphology from the bare silica particles (Figure 3A and C) to the polystyrene-bound silica particles (Figure 3B and D) in different scale magnification. The surface of modified particles was much smoother than bare particles owing to the layer of polystyrene. TEM images of hierarchical periodic pore structures are clear and very informative (Figure 3F) compared with bare particles (Figure 3E). The diversity in particle shapes enabled partial monolithic structures (some through-flow channels) in the bed when the particles were packed in a column. Thus, the permeability of the column based on the ground silica monolith particles is better than that of the column based on the spherical silica particles. Figure 3 Open in new tabDownload slide Microscopic views of silica monolith particles: SEM images of (A and C) bare particles and (B and D) polystyrene-modified particles; (E) TEM image of bare particles and (F) polystyrene-bound TEM image. Figure 3 Open in new tabDownload slide Microscopic views of silica monolith particles: SEM images of (A and C) bare particles and (B and D) polystyrene-modified particles; (E) TEM image of bare particles and (F) polystyrene-bound TEM image. PSD The PSD of the packed particles in HPLC columns has always been recognized as an important factor influencing their performance. Intuitively, it seems desirable to use the HPLC packing materials of narrow PSD. The number-based and volume-based numerical particle size data are comparatively summarized in Table I. It is convenient and reasonable to use the volume-based d(0.5) value as the average particle size (23–28). The volume-based d(0.5) was increased from 2.679 to 4.094 μm for the change from bare particles to polystyrene-bound particles. The volume-based PSD curves of silica monolith particles before and after modification are compared in Figure 4. As shown in Figure 4, the bare silica monolith particles were free of very fine particles, and the particle size was significantly increased by polystyrene modification. Table I Comparison of Particle Size Distribution of Bare Silica Monolith Particles with that of Polystyrene-Modified Particles . Silica monolith particles . Ligand-stationary phase . . d(0.1)a . d(0.5)b . d(0.9)c . d(0.1)a . d(0.5)b . d(0.9)c . Number 1.035 1.506 2.401 1.36 1.960 2.980 Volume 1.796 2.679 3.995 2.028 4.094 7.627 . Silica monolith particles . Ligand-stationary phase . . d(0.1)a . d(0.5)b . d(0.9)c . d(0.1)a . d(0.5)b . d(0.9)c . Number 1.035 1.506 2.401 1.36 1.960 2.980 Volume 1.796 2.679 3.995 2.028 4.094 7.627 aParticle diameter corresponding to the integrated area ratio of 0.1 when integrated in the range of 0–d diameter. bParticle diameter corresponding to the integrated area ratio of 0.5 when integrated in the range of 0–d diameter. cParticle diameter corresponding to the integrated area ratio of 0.9 when integrated in the range of 0–d diameter. Open in new tab Table I Comparison of Particle Size Distribution of Bare Silica Monolith Particles with that of Polystyrene-Modified Particles . Silica monolith particles . Ligand-stationary phase . . d(0.1)a . d(0.5)b . d(0.9)c . d(0.1)a . d(0.5)b . d(0.9)c . Number 1.035 1.506 2.401 1.36 1.960 2.980 Volume 1.796 2.679 3.995 2.028 4.094 7.627 . Silica monolith particles . Ligand-stationary phase . . d(0.1)a . d(0.5)b . d(0.9)c . d(0.1)a . d(0.5)b . d(0.9)c . Number 1.035 1.506 2.401 1.36 1.960 2.980 Volume 1.796 2.679 3.995 2.028 4.094 7.627 aParticle diameter corresponding to the integrated area ratio of 0.1 when integrated in the range of 0–d diameter. bParticle diameter corresponding to the integrated area ratio of 0.5 when integrated in the range of 0–d diameter. cParticle diameter corresponding to the integrated area ratio of 0.9 when integrated in the range of 0–d diameter. Open in new tab Figure 4 Open in new tabDownload slide Comparison of volume-based particle size distribution of silica monolith particles before modification (square) and after modification (circle). Figure 4 Open in new tabDownload slide Comparison of volume-based particle size distribution of silica monolith particles before modification (square) and after modification (circle). BET/BJH analysis The BET/BJH analysis results of this study in comparison with those of previous study are summarized in Table II. The BJH adsorption pore size distribution plots for the bare and modified silica monolith particles are compared in Figure 5. The average pore size of silica monolith particles decreased from 269 to 199 Å after one-pot modification with styrene ligand, as shown in Table II. The pore volume of silica monolith particles has been decreased from 0.75 to 0.43 cm3/g, demonstrating formation of some polystyrene layer on the inner pore surface. The BET-specific surface area of silica monolith particles was decreased from 106 to 81 m2/g after polystyrene modification. Briefly, the data altogether support the fact that the bare silica monolith particles were successfully modified with styrene and EDMA primarily on the outer surface of particles and subsidiarily on the surface of inner pores. Table II The BET/BJH Analysis Data of This Study in Comparison with Those of Previous Studies . Bare silica monolith particles . Ligand-bound silica particles . . Reference (30) . Current study . Reference (30) . Current study . Pore size (Å) 366 269 245 199 Pore volume (cm3/g) 0.97 0.75 0.73 0.43 Surface area (m2/g) 114 106 104 81 . Bare silica monolith particles . Ligand-bound silica particles . . Reference (30) . Current study . Reference (30) . Current study . Pore size (Å) 366 269 245 199 Pore volume (cm3/g) 0.97 0.75 0.73 0.43 Surface area (m2/g) 114 106 104 81 Open in new tab Table II The BET/BJH Analysis Data of This Study in Comparison with Those of Previous Studies . Bare silica monolith particles . Ligand-bound silica particles . . Reference (30) . Current study . Reference (30) . Current study . Pore size (Å) 366 269 245 199 Pore volume (cm3/g) 0.97 0.75 0.73 0.43 Surface area (m2/g) 114 106 104 81 . Bare silica monolith particles . Ligand-bound silica particles . . Reference (30) . Current study . Reference (30) . Current study . Pore size (Å) 366 269 245 199 Pore volume (cm3/g) 0.97 0.75 0.73 0.43 Surface area (m2/g) 114 106 104 81 Open in new tab Figure 5 Open in new tabDownload slide Comparison of the BJH adsorption pore size distribution between the bare silica monolith particles (square) and the styrene-modified silica monolith particles (circle). Figure 5 Open in new tabDownload slide Comparison of the BJH adsorption pore size distribution between the bare silica monolith particles (square) and the styrene-modified silica monolith particles (circle). Elemental analysis It included 1.32% carbon, 0.78% oxygen and 0.24% hydrogen according to elemental analysis after the silica monolith particles modified with γ-MAPS. After the one-pot polymerization of styrene and EDMA, the elemental analysis data of carbon 7.68%, oxygen 1.83% and hydrogen 0.73%, respectively. The oxygen content was increased, which indicated that the free methacrylate groups exist on the silica monolith particles. These reasonable results demonstrated that the cross-linked network copolymer layer was properly formed on the surface of silica monolith particles. HPLC chromatographic performance The excellent separation efficiency was obtained for the phase of this study and previous study (30), as shown in Table III. The chromatogram obtained in the optimized HPLC elution conditions is shown in Figure 6. The average plate number over five analytes was 39,300 per column, much better than that of three-step modification. Not only theoretical plates but also separation resolution was found superior, and all the test mixtures were better separated in a wider retention time range. The one-pot approach modification showed better separation efficiency than three-step modification in this study. The stabile cross-linked network polymer layer bound on the surface using one-pot modification, whereas the polymer chains on the surface by three-step reaction. During the column packing procedure, the polymer chains are easy collapsed using high packing pressure, resulting poor packing quality of the column. Table III The Average Plate Numbers Based on Three Columns of This Study in Comparison with the Data of Reference (30) Solute . Reference (30) . Current study . Phenol 37,200 ± 500 41,000 ± 500 Acetophenone 36,500 ± 600 40,300 ± 700 4-Methyl-2-nitroaniline 35,600 ± 500 39,200 ± 400 Benzene 35,200 ± 700 38,400 ± 600 Toluene 34,400 ± 700 37,900 ± 800 Average 35,500 39,300 Solute . Reference (30) . Current study . Phenol 37,200 ± 500 41,000 ± 500 Acetophenone 36,500 ± 600 40,300 ± 700 4-Methyl-2-nitroaniline 35,600 ± 500 39,200 ± 400 Benzene 35,200 ± 700 38,400 ± 600 Toluene 34,400 ± 700 37,900 ± 800 Average 35,500 39,300 Open in new tab Table III The Average Plate Numbers Based on Three Columns of This Study in Comparison with the Data of Reference (30) Solute . Reference (30) . Current study . Phenol 37,200 ± 500 41,000 ± 500 Acetophenone 36,500 ± 600 40,300 ± 700 4-Methyl-2-nitroaniline 35,600 ± 500 39,200 ± 400 Benzene 35,200 ± 700 38,400 ± 600 Toluene 34,400 ± 700 37,900 ± 800 Average 35,500 39,300 Solute . Reference (30) . Current study . Phenol 37,200 ± 500 41,000 ± 500 Acetophenone 36,500 ± 600 40,300 ± 700 4-Methyl-2-nitroaniline 35,600 ± 500 39,200 ± 400 Benzene 35,200 ± 700 38,400 ± 600 Toluene 34,400 ± 700 37,900 ± 800 Average 35,500 39,300 Open in new tab The column-to-column and intra-day to inter-day reproducibility were checked by packing three columns with three different batches of polystyrene-bound silica monolith particles, and the relative standard deviation in separation efficiency was at least better than 3.0% (Table IV). The retention time and resolution reproducibility was also found to be better than 2.0%. Figure 6 Open in new tabDownload slide The first chromatogram was for KNO3, the second one was the column packed with bare particles and the third one was the column packed with stationary phase for the test mixture. <Elution Order> A: phenol, B: acetophenone, C: 4-methyl-2-nitroaniline, D: benzene, E: toluene. Figure 6 Open in new tabDownload slide The first chromatogram was for KNO3, the second one was the column packed with bare particles and the third one was the column packed with stationary phase for the test mixture. <Elution Order> A: phenol, B: acetophenone, C: 4-methyl-2-nitroaniline, D: benzene, E: toluene. Table IV The Average and Relative Standard Deviation Data of Column Plate Count (N), Resolution (R) and Retention Time Based on Three Different Batches of Columns Analytes . Reproducibility . “N” values . Retention time (min) . Resolution (R) . Average . %RSD . Average . %RSD . Average . %RSD . Phenol 41,000 0.32 7.7 0.18 0.94 0.43 Acetophenone 40,300 1.05 8.6 0.26 1.15 0.62 4-Methyl-2-nitroaniline 39,200 0.86 9.7 0.42 1.41 1.03 Benzene 38,400 1.14 11.1 0.59 1.79 0.84 Toluene 37,900 2.12 12.6 1.03 2.18 1.53 Average 39,300 9.9 1.50 Analytes . Reproducibility . “N” values . Retention time (min) . Resolution (R) . Average . %RSD . Average . %RSD . Average . %RSD . Phenol 41,000 0.32 7.7 0.18 0.94 0.43 Acetophenone 40,300 1.05 8.6 0.26 1.15 0.62 4-Methyl-2-nitroaniline 39,200 0.86 9.7 0.42 1.41 1.03 Benzene 38,400 1.14 11.1 0.59 1.79 0.84 Toluene 37,900 2.12 12.6 1.03 2.18 1.53 Average 39,300 9.9 1.50 Open in new tab Table IV The Average and Relative Standard Deviation Data of Column Plate Count (N), Resolution (R) and Retention Time Based on Three Different Batches of Columns Analytes . Reproducibility . “N” values . Retention time (min) . Resolution (R) . Average . %RSD . Average . %RSD . Average . %RSD . Phenol 41,000 0.32 7.7 0.18 0.94 0.43 Acetophenone 40,300 1.05 8.6 0.26 1.15 0.62 4-Methyl-2-nitroaniline 39,200 0.86 9.7 0.42 1.41 1.03 Benzene 38,400 1.14 11.1 0.59 1.79 0.84 Toluene 37,900 2.12 12.6 1.03 2.18 1.53 Average 39,300 9.9 1.50 Analytes . Reproducibility . “N” values . Retention time (min) . Resolution (R) . Average . %RSD . Average . %RSD . Average . %RSD . Phenol 41,000 0.32 7.7 0.18 0.94 0.43 Acetophenone 40,300 1.05 8.6 0.26 1.15 0.62 4-Methyl-2-nitroaniline 39,200 0.86 9.7 0.42 1.41 1.03 Benzene 38,400 1.14 11.1 0.59 1.79 0.84 Toluene 37,900 2.12 12.6 1.03 2.18 1.53 Average 39,300 9.9 1.50 Open in new tab Discussion The discussion of the van Deemter plots was obtained in the developed 1.0 × 150 mm column packed with the polystyrene-bound phase. The total porosity of our column was found to be 0.62 based on the retention time of KNO3. The H values are <7.5 μm in the whole flow rate range, which means that the N value per column is at least >19,000 for the flow rate range of 5–60 μL/min. The optimized flow rate was 25 μL/min where the corresponding H value (average over five different analytes) was 3.82 μm in Figure 7a. In addition, the van Deemter plots of developed column and commercial YMC C18 column (15 cm × 2.1 mm, 2.7 μm) for a selected analyte 4-methyl-2-nitroaniline were compared in Figure 7b. The minimum of van Deemter curve is often used as a performance benchmark of the individual column tested. The commercial column exhibited a minimum plate height of 9.10 mm, whereas the OT-CLC column of this study showed a minimum of 3.82 mm. Figure 7 Open in new tabDownload slide (a) The van Deemter plots obtained with the column (1 × 150 mm) packed with the polystyrene-bound silica monolith particles in 60/40 acetonitrile/water with 0.1% TFA; (b) the van Deemter plots of developed column and commercial YMC C18 column for a selected analyte 4-methyl-2-nitroaniline. Figure 7 Open in new tabDownload slide (a) The van Deemter plots obtained with the column (1 × 150 mm) packed with the polystyrene-bound silica monolith particles in 60/40 acetonitrile/water with 0.1% TFA; (b) the van Deemter plots of developed column and commercial YMC C18 column for a selected analyte 4-methyl-2-nitroaniline. Conclusions In this study, the incorporation of styrene based on ground silica particles was developed by one-pot approach, whereas EDMA used as cross-linking agent for preparation stationary phase in HPLC. The nitrogen adsorption–desorption, PSD and elemental analysis data were demonstrated for the successfully modification. The sol–gel ground silica monolith particles without very fine particles have been prepared. The particles were successfully modified to have a stabile network polymer layer with good surface morphology by one-pot polymerization and packed in the 1.0 × 150 mm columns to show the separation efficiencies of 39,300 plates per column, which is better than three-step modification. The reproducibility in separation efficiency based on three columns packed with three different batches of stationary phase was at least better than 3%. This study offers a promising vision towards commercialization of chromatographic phases based on ground silica monolith particles. Acknowledgment This research was supported by the PhD Program through Jiangxi University of Traditional Chinese Medicine (5152000407) and Science and Technology Project of Education Department of Jiangxi Province (GJJ201249). 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TI - Polystyrene Immobilized Sol–Gel Ground Silica Monolith Particles Using One-Pot Reaction of Enhanced Separation Efficiency
JF - Journal of Chromatographic Science
DO - 10.1093/chromsci/bmab032
DA - 2021-03-27
UR - https://www.deepdyve.com/lp/oxford-university-press/polystyrene-immobilized-sol-gel-ground-silica-monolith-particles-using-3HbKTEicZn
SP - 1
EP - 1
VL - Advance Article
IS - 
DP - DeepDyve
ER -