The influence of the synthesis pressure on the chromatographic properties of poly(divinylbenzene-<Emphasis Type="Italic">co</Emphasis>-ethylvinylbenzene-<Emphasis Type="Italic">co</Emphasis>-2-hydroxyethyl methacrylate) monolithic columns

Monolithic columns based on copolymer of divinylbenzene (DVB), ethylvinylbenzene (EVB), and 2-hydroxyethyl methacrylate (HEMA) were prepared and applied to the separation of low-molecular-weight aromatic compounds. The monoliths were synthesized via thermally initiated free-radical polymerization in confines of stainless steel tubes with dimensions of 100 × 4.3 mm. In order to compensate for the polymer shrinkage during the synthesis and prevent the monolith from detachment from the column wall, the polymerization was conducted under nitrogen pressure. The excess pressure was varied from 0 bar to 9 bar. The synthesis under pressure was shown to improve the peak shapes and column efficiency in comparison with the synthesis in the closed tube. The optimum pressure for poly(DVB-co-EVB-co-HEMA) monoliths was found to be 3 bar. The efficiency of the column obtained at 3 bar is 13 500 TP/m for propylbenzene (k′ = 6) and 38 300 TP/m for uracil (k′ = 0).     

Preparation and evaluation of a neutral methacrylate-based monolithic column for hydrophilic interaction stationary phase by pressurized capillary electrochromatography

A polar and neutral polymethacrylate-based monolithic column was evaluated as a hydrophilic interaction capillary electrochromatography (HI-CEC) stationary phase with small polar–neutral or charged solutes. The polar sites on the surface of the monolithic solid phase responsible for hydrophilic interactions were provided from the hydroxy and ester groups on the surface of the monolithic stationary phase. These polar functionalities also attract ions from the mobile phase and impart the monolithic solid phase with a given zeta potential to generate electro-osmotic flow (EOF). The monolith was prepared by in situ copolymerization of a neutral monomer 2-hydroxyethyl methacrylate (HEMA) and a polar cross-linker with hydroxy group, pentaerythritol triacrylate (PETA), in the presence of a binary porogenic solvent consisting cyclohexanol and dodecanol. A typical HI-CEC mechanism was observed on the neutral polar stationary phase for both neutral and charged analytes. The composition of the polymerization mixture was systematically altered and optimized by altering the amount of HEMA in the polymerization solution as well as the composition of the porogenic solvent. The monoliths were tested in the pCEC mode. The resulting monoliths had different characteristics of hydrophilicity, column permeability, and efficiency. The effects of pH, salt concentration, and organic solvent content on the EOF velocity and the separation of nucleic acids and nucleosides on the optimized monolithic column were investigated. The optimized monolithic column resulted in good separation and with greater than 140,000 theoretical plates/m for pCEC.     

Preparation and characterization of lauryl methacrylate-based monolithic microbore column for reversed-phase liquid chromatography

Poly(lauryl methacrylate-co-ethylene dimethacrylate) monoliths were in situ synthesized within the confines of a silicosteel tubing of 1.02 mm i.d. and 1/16" o.d. for microbore reversed-phase HPLC. In order to obtain practically useful monoliths with adequate column efficiency, low flow resistance, and good mechanical strength, some parameters such as total monomer concentration (%T), cross-linking degree (%C) and polymerization temperature were optimized. High-efficiency monoliths were successfully obtained by thermal polymerization of a monomer mixture (40%T, 10%C) with a binary porogenic solvent consisting of 1-propanol and 1,4-butandiol (7:4, v/v) at a high temperature of 90 °C. The morphology and porous structure of the resulting monoliths were assessed by scanning electron microscope (SEM) and inverse size exclusion chromatography (ISEC), while the column performance was evaluated through the separations of a series of alkylbenzenes in acetonitrile-water (50:50, v/v) eluent. At a normal flow rate of 50 μL/min (corresponding to 1.66 mm/s), the optimized monolithic columns typically exhibited theoretical plate numbers of 6000 plates/10 cm-long column for amylbenzene (k>40), and the pressure drop was always less than 1 MPa/10 cm. The monoliths, which were chemically anchored to the tube inner wall surface using a bifunctional silylation agent, exhibited adequate mechanical strength of up to 12-13 MPa, and were properly operated at 10 times higher flow rate than normal, reducing the separation time to one tenth. The lauryl methacrylate-based monolithic column was applied to a rapid and efficient separation of ten common proteins such as aprotinin, ribonuclease A, insulin, cytochrome c, trypsin, transferrin, conalbumin, myoglobin, β-amylase, and ovalbumin in the precipitation-redissolution mode. Using a linear CH(3)CN gradient elution at a flow rate of 500 μL/min (10-times higher flow rate), 10 proteins were baseline separated within 2 min.     

Ultra high-performance liquid chromatography of porphyrins in clinical materials: column and mobile phase selection and optimisation

Ultra high-performance liquid chromatographic (UHPLC) systems on columns packed with materials ranging from 1.9 to 2.7 μm average particle size were assessed for the fast and sensitive analysis of porphyrins in clinical materials. The fastest separation was achieved on an Agilent Poroshell C(18) column (2.7 μm particle size, 50 × 4.6 mm i.d.), followed by a Thermo Hypersil Gold C(18) column (1.9 μm particle size, 50 × 2.1 mm i.d.) and the Thermo Hypersil BDS C(18) column (2.4 μm particle size, 100 × 2.1 mm i.d.). All columns required a mobile phase containing 1 m ammonium acetate buffer, pH 5.16, with a mixture of acetonitrile and methanol as the organic modifiers for optimum resolution of the type I and III isomers, particularly for uroporphyrin I and III isomers. All UHPLC columns were suitable and superior to conventional HPLC columns packed with 5 μm average particle size materials for clinical sample analysis.     

烷基酚聚氧乙烯醚在不同液相色谱分离模式中的分离研究

考察了烷基酚聚氧乙烯醚在反相色谱、正相键合色谱、硅胶吸附色谱、体积排阻色谱4种不同液相色谱分离模式中的分离效果,分别采用Kromasil C_(18)(250 mm× 4.6 mm,5 μm)、Agilent ZORBAX NH2(250 mm× 4.6 mm,5 μm)、Waters Spherisorb S3W(150 mm×2.0 mm,3 μm)和Shodex MSpak GF-310 2D(150 mm×2.0 mm,5 μm)色谱柱,以225 nm为紫外检测波长,对不同液相色谱分离模式的流动相组成、梯度洗脱条件、柱温、流速等进行了优化,并对烷基酚聚氧乙烯醚在不同液相色谱分离模式中的保留机理进行了初步探讨.结果表明,正相键合色谱实现了烷基酚聚氧乙烯醚的最佳分离;硅胶吸附色谱和体积排阻色谱的分离效果较正相键合色谱稍差.     

Preparation and Evaluation of Long Chain Alkyl Methacrylate Monoliths for Capillary Chromatography

This work describes the fabrication of long chain alkyl methacrylate monolithic materials for use as stationary phases in capillary liquid chromatography. After capillary inner wall surface activation with 3-(trimethoxysilyl)propyl methacrylate, monoliths were formed by copolymerization of either lauryl or stearyl methacrylate (LMA or SMA) with ethylene dimethacrylate (EDMA) as crosslinker, in the presence of azobisisobutyronitrile (AIBN) as initiator and a mixture of porogenic solvents including water, 1-propanol and 1,4-butanediol. The composition of the polymerization mixture was changed in terms of monomer, crosslinker and porogen ratio composition, in order to compare the influence of these parameters. The monoliths were prepared in 320 ??m i.d. and 200 mm length capillaries. The column morphology was characterized by optical microscopy and scanning electron microscopy (SEM). Total porosity and permeability of each column were calculated using uracil as unretained material by measuring the pressure drop across the columns as a function of linear velocity. The microglobule average size for each column was also determined using Hagen?CPoiseuille equation and compared with the SEM images. As expected, a decrease of the porogen to monomer ratio corresponded to smaller microglobules and a lower total porosity. The columns were then chromatographically evaluated; good results were obtained when these capillaries were used to separate mixtures of phenols, aromatics and drug compounds.     

Polymethacrylate-type monoliths functionalized with chiral amino phosphonic acid-derived strong cation exchange moieties for enantioselective nonaqueous capillary electrochromatography and investigation of the chemical composition of the monolithic polymer

In situ prepared monolithic poly(glycidyl methacrylate-co-ethylene dimethacrylate) (poly(GMA-co-EDMA)) capillary columns were activated to reactive thiol-monoliths and subsequently functionalized with (S)-N-(4-allyloxy-3,5-dichlorobenzoyl)-2-amino-3,3-dimethylbutanephosphonic acid as chiral selector by radical addition to afford enantioselective strong cation exchanger (SCX) capillary columns (100 microm inner diameter (ID)). These monolithic capillaries were devised for the enantioseparation of chiral bases by nonaqueous and aqueous capillary electrochromatography (CEC) and the results obtained for mefloquine and its tert-butylcarbamate as test compounds were compared to those obtained with particulate silica-based analogs (packed columns). Despite abolishment of nonspecific ionic interactions between the cationic solutes and residual silanols that may diminish separation factors of the silica-based chiral SCX particles, the poly(GMA-co-EDMA)-supported SCX monolith did not, as expected, show better enantioselectivities, which was assumed to be due to detrimental nonspecific interactions between the analytes and the lipophilic polymer backbone. In order to minimize these unfavorable contributions, less lipophilic monoliths were developed by copolymerization of different amounts of the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) with GMA and EDMA, leading to GMA-co-HEMA-co-EDMA-terpolymeric monoliths. By this increase of the hydrophilicity of the monolithic support the enantioselectivity of the resultant SCX stationary phase could be enhanced and reached values comparable to the packed silica-based enantioselective SCX capillaries. Additionally, the mobile phase composition and other variables were examined and it could be shown that the separation factors are considerably affected by diverse parameters such as acetonitrile-methanol ratio and type and concentration of the counterion. Mefloquine enantiomers could be separated with alpha-values up to 1.56 and a maximum plate count of ca. 60,000 m(-1) could be achieved.     

Fast separation of low molecular weight analytes on structurally optimized polymeric capillary monoliths

The optimization of recently introduced tetrakis(4-vinylbenzyl)silane (TVBS)-derived capillary monoliths to suit the fast separation of small molecules was accomplished by simultaneous changes in both the stoichiometry of the polymerization mixture and in the polymerization temperature. Four types of monoliths were prepared by varying the polymerization temperature within 60 and 65 °C as well as by changing the monomer content between 15.0 and 20.0 wt.%. Changes in the porosity and morphology of the capillary columns were studied applying inverse size exclusion chromatography (ISEC), nitrogen sorption (BET), and scanning electron microscopy (SEM). All monoliths were used for the reversed-phase separation of various sets of low molecular weight analytes such as alkyl benzenes, aryl amines, carboxylic acids, and a mixture of phenols and carbonyl compounds. Comparable efficiency and performance towards the different sets of analytes were observed. With optimized monolith structures, the fast separation of six-alkyl benzenes was accomplished within less than 2 min. This was made possible by a high linear solvent flow (10 mm/s) at low column pressure drops (<15 MPa).     

一种聚甲基丙烯酸酯类亲水作用毛细管电色谱整体柱的制备与评价

以2-羟基乙基甲基丙烯酸酯(HEMA)为单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,制备了亲水分离模式的聚HEMA-co-EDMA新型毛细管电色谱(CEC)整体柱。考察了整体柱的结构特征及其CEC性能,研究了极性物质的保留行为,并对其可能的保留机理进行了探讨。所制备的整体柱稳定性好,固定相表面带有极性羟基功能团,不仅能提供亲水相互作用位点,且能吸附流动相中的阴离子产生阳极电渗流(EOF)。在流动相中乙腈含量较高(＞62%,体积分数)的条件下,整体柱表现出典型的亲水作用,实现了对核苷、碱基和苯胺类带有碱性的强极性化合物的高效分离,并成功分离了苯酚类、苯甲酸类等中性或酸性的极性化合物。     

Towards porous polymer monoliths for the efficient, retention-independent performance in the isocratic separation of small molecules by means of nano-liquid chromatography

We have investigated the free-radical copolymerization dynamics of styrene and divinylbenzene in the presence of micro- and macro-porogenic diluents in 100 μm I.D. sized molds under conditions of slow thermal initiation leading to (macro)porous poly(styrene-co-divinylbenzene) monolithic scaffolds. These specifically designed experiments allowed the quantitative determination of monomer specific conversion against polymerization time to derive the porous polymer scaffold composition at each desirable copolymerization stage after phase separation. This was carried out over a time scale of 3h up to 48 h polymerization time, enabling the efficient and repeatable termination of the polymerization reactions. In parallel, the porous and hydrodynamic properties of the derived monolithic columns were thoroughly studied in isocratic nano-LC mode for the reversed-phase separation of a homologous series of small retained molecules. At the optimized initiator concentration, polymerization temperature and time, the macroporous poly(styrene-co-divinylbenzene) monoliths show a permanent mesoporous pore space, which was readily observable by electron microscopy and indicated by nitrogen adsorption experiments. Under these conditions, we consistently find a polymer scaffold composition which suggests a high degree of cross-linking and thus minimum amount of gel porosity. These columns reveal a retention-insensitive plate height in the separation of small retained molecules which only slightly decreases at increased linear mobile phase velocity. As the polymerization progresses, a build-up of less-densely cross-linked material occurs, which is directly reflected in the observed consistent increase in retention and plate heights. This leads to a significant deterioration in overall isocratic separation performance. The decrease in performance is ascribed in particular to the increased mass transfer resistance governing the monoliths' performance over the whole linear chromatographic flow velocity range at polymerization times significantly higher than that of phase separation. The performance of the optimized monoliths only becomes limited by fluid dispersion due to the poorly structured macroporous pore space.     

Preparation and application of hydrophobic hybrid monolithic columns containing polyhedral oligomeric silsesquioxanes for capillary electrochromatography

Hydrophobic organic-inorganic hybrid monolithic columns were synthesized via thermally initiated free radical polymerization with the confines of 75 μm id capillary using a polyhedral oligomeric silsesquioxane (POSS) reagent containing eight or more methacrylate groups as the crosslinker. Three organic functional monomers, butyl methacrylate (BuMA), lauryl methacrylate (LMA) and methacrylic acid (MAA), were selected and copolymerized with the POSS in the presence of 1-propanol and 1,4-butanediol to prepare the poly(POSS-co-BuMA), poly(POSS-co-LMA), and poly(POSS-co-MAA) monoliths, respectively. The 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) was copolymerized as ionizable monomer into the poly(POSS-co-BuMA) and poly(POSS-co-LMA) for the generation of EOF in capillary electrochromatography (CEC). A hybrid poly(POSS-co-LMA-co-MAA) monolith was also similarly prepared by copolymerizing ternary monomers of POSS, LMA, and MAA, and compared with poly(POSS-co-BuMA), poly(POSS-co-LMA), and poly(POSS-co-MAA) monoliths. The resulting four kinds of POSS-contained hybrid monoliths exhibited good permeability and mechanical stability. Their column efficiencies were evaluated by the separation of alkylbenzene homologues and polar compounds in CEC. The results indicated that the highest efficiencies of 194,100 and 102,100 theoretical plates per meter for thiourea and benzene were obtained on the poly(POSS-co-LMA-co-MAA) monolith. Additionally, the poly(POSS-co-LMA-co-MAA) monolith exhibited better selectivity for separation of polar compounds than those of other hybrid monoliths.     

Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivity

A new chiral monomer derived from cinchona alkaloid, namely O-9-(tert-butylcarbamoyl)-11-[2-(methacryloyloxy)ethylthio]-10,11-dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2-hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1-dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O-9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross-linking (10 wt% related to total monomers) and a pore diameter of about 1 microm in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C-term contribution to peak broadening) and more homogeneous flow profile (smaller A-term). Most importantly, as expected the new poly(1-co-HEMA-co-EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4-co-HEMA-co-EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine- and quinidine-derived monomers. Fluorescence-labeled 9-fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7-dimethylaminosulfonyl-1,3,2-benzoxadiazol-4-yl (DBD), carbazole-9-carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100,000 and 200,000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in-line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency.     

Monolithic capillary columns based on pentaerythritol acrylates for molecular‐size‐based separations of synthetic polymers

Monolithic capillary columns based on pentaerythritol triacrylate and pentaerythritol tetraacrylate were synthesized using different compositions of polymerization mixtures and different polymerization conditions. The impact of porogen type and porogen/monomer ratio on the porosity of synthesized monoliths was investigated. Porogen type appears to be the main factor influencing the separating properties of the monolithic sorbent. Using optimal polymerization conditions (porogen type, porogen/monomer ratio, reaction temperature, time etc.) monoliths with a porous structure optimized for polymer separations can be obtained. The monolithic capillary columns containing porous sorbents with optimized porosity are capable of separating 10 to 12 polystyrene standards in one chromatographic run utilizing both size exclusion chromatography and hydrodynamic chromatography separation mechanisms.     

Amino-Functionalized Monolithic Poly(glycidyl methacrylate-<Emphasis Type="Italic">co</Emphasis>-divinylbenzene) Ion-Exchange Stationary Phases for the Separation of Oligonucleotides

Monolithic capillary columns were prepared by thermal initiated copolymerization of glycidyl methacrylate (GMA) and divinylbenzene (DVB) inside silanized 200 µm i.d. fused silica capillaries. Polymerization mixtures containing different amounts of porogen (1-decanol and tetrahydrofuran (THF)) and different ratios of monomer and crosslinker were used for synthesis. For characterization the pore size distribution profiles of the resulting monoliths were determined by mercury intrusion porosimetry. The morphology of the copolymer was investigated by scanning electron micrographs (SEM). A high linear dependence between flow rate and pressure drop was achieved which indicates that the polymer is pressure-stable even at high flow rates. After characterization the produced GMA-DVB monoliths, which contain reactive epoxide groups, were modified by reaction with diethylamine to obtain a poly(3-diethylamino-2-hydroxypropyl methacrylate-co-divinylbenzene) ion-exchange monolithic stationary phase. The synthesized monoliths contain ionizable amino groups that are useful for anion-exchange chromatography (AEC). Poly(3-diethylamino-2-hydroxypropyl methacrylate-co-divinylbenzene) monolithic columns allowed a fast and highly efficient separation of a homologous series of phosphorylated oligothymidylic acids [d(pT)_12-18]. Since durability is an important parameter of chromatographic column characterization, the separation performance for d(pT)_12-18 in a freshly produced capillary column and on the same column after 100 chromatographic runs was compared.     

Dynamic evaluation of polypropylene capillary‐channeled fibers as a stationary phase in high‐performance liquid chromatography

Polypropylene (PP) capillary‐channeled polymer (C‐CP) fiber stationary phases are investigated for applications in HPLC. Specifically, the roles that fiber size and shape, linear velocity, interstitial fraction, and column inner diameter play in separation efficiency were evaluated using a uracil and butylparaben mixture eluted under isocratic conditions. Four fiber types, having nominal diameters ranging from 30 to 65 μm, were used in 250 mm × 2.1 mm columns. Optimum flow characteristics, as judged by plate height and resolution, were observed for 40 μm diameter PP C‐CP fibers packed at an interstitial fraction of ～0.63, over a broad range of linear velocities (～2 to 37 mm/s). The influence of column inner diameter was studied on 1.5, 2.1, and 4.6 mm columns packed at the optimal interstitial fraction. The best performing column in terms of plate height and resolution was the 2.1 mm inner diameter. C‐CP columns were also evaluated for the separation of a protein mixture composed of ribonuclease A, cytochrome c, and transferrin. Results obtained with the biomacromolecules mixture validate the optimal structural and operative conditions determined with the small solutes, laying the groundwork towards biomacromolecule applications, focusing more on the chemical aspects of separations.     

The Effects of the Column Length on the Efficiency of Capillary Zwitterionic Organic Polymer Monolithic Columns in HILIC Chromatography

Organic polymer monolithic columns of different lengths have been prepared in 320 µm i.d. fused silica capillary by in situ radical polymerization of N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium betaine as a zwitterionic functional monomer and bisphenol A glycerolate dimethacrylate as a crosslinking monomer in the presence of porogenic solvents. The zwitterionic monolithic columns are intended for separations of polar compounds in hydrophilic interaction chromatography (HILIC). The effects of the capillary column length, from 115 to 175 mm, on separation efficiency, were investigated under HILIC conditions, using 95:5 acetonitrile in water as the mobile phase. The extra-column contributions to band broadening significantly decrease the efficiency (apparent height equivalent to a theoretical plate), especially for weakly retained samples, and increase with diminishing column length. The experimental height equivalents of theoretical plate, HETP, were corrected for the extra-column contributions, which were determined for a series of columns by extrapolation to zero column length. On a 175 mm long column, the column efficiency, HETP = 16.5 μm, measured at the optimum linear flow velocity of 0.5 mm s⁻¹, improved to HETP = 5 µm, after correction for extra-column contributions. For more strongly retained small polar compounds, interactions with zwitterionic groups and (or) water adsorbed inside the pores decrease the column efficiency at higher flow rates.

     

Preparation of monolithic capillary columns for capillary electrochromatography by γ-ray irradiation

A novel approach is introduced and evaluated for the preparation of silica-based monoliths by a sol–gel technique where in situ polymerization was carried out by γ-ray irradiation within the capillary. The γ-radiation-initiated synthesis generated radicals directly on the monomer, thereby avoiding use of any initiator. The chromatographic behavior of the capillary monolithic columns was studied in the modes of CEC, p-CEC and low pressure-driven separation, all of which exhibited reversed-phase character. Various operational parameters, such as column temperature, separation voltage, acetonitrile content and buffer pH, were varied to assess their influence on column performance in the separation of a series of neutral compounds including thiourea, benzene, toluene, ethyl benzene, biphenyl and naphthalene. A scanning electron micrograph of a cross-section of the capillary column showed that the gel took the form of a spherical particle aggregate and adhered to the column inner wall. It provided a viable alternative to either thermally initiated or photo polymerization for the preparation of monolithic columns.     

布洛芬高分子前体药物及纳米微球的合成和表征

将非甾体消炎药布洛芬以共价键连接到舍双键的甲基丙烯酸-2-羟基乙酯(HEMA)上,制成含布洛芬药物的单体,进而通过自聚或共聚,合成了含布洛芬的高分子药物;采用乳液聚合方法制备了高分子药物蚋米微球。研究了影响聚合反应的有关因素,并对所合成的产物用^1H-NMR,GPC和TEM等检测手段进行了表征。     

The impact of extra-column band broadening on the chromatographic efficiency of 5 cm long narrow-bore very efficient columns

Small columns packed with core-shell and sub-2 μm totally porous particles and monolith columns are very popular to conduct fast and efficient chromatographic separations. In order to carry out fast separations, short (2-5 cm) and narrow-bore (2-2.1 mm) columns are used to decrease the analyte retention volume. Beside the column efficiency, another significant issue is the extra-column band-spreading. The extra-column dispersion of a given LC system can dramatically decrease the performance of a small very efficient column. The aim of this study was to compare the extra-column peak variance contribution of several commercially available LC systems. The efficiency loss of three different type 5 cm long narrow bore, very efficient columns (monolith, sub-2 μm fully porous and sub-2 μm core-shell packing) as a function of extra-column peak variance, and as a function of flow rate and also kinetic plots (analysis time versus apparent column efficiency) are presented.     

Fabrication of a poly(styrene-octadecene-divinylbenzene) monolithic column and its comparison with a poly(styrene-divinylbenzene) monolithic column for the separation of proteins

In this paper, a poly(styrene-octadecene-divinylbenzene) (PS-OD-DVB) monolithic column was prepared in one step by introducing a C18 carbon chain as monomer. N,N-Dimethylformamide and decanol served as porogens to make a homogeneous polymerization mixture in a fused silica capillary (320 microm inner diameter). Its physical and chromatographic properties were compared with those of poly(styrene-divinylbenzene) (PS-DVB) monolithic column, which was also fabricated by in-situ polymerization in a fused silica capillary with the same inner diameter. Six standard proteins were used to evaluate the columns and their potential application for the separation of human hemoglobin was also discussed. It was shown that the PS-OD-DVB and PS-DVB monoliths appeared to have similar efficiency for rapid separation of six proteins within 3.5 min. The PS-OD-DVB monolith was found to have higher loading capacity and higher resolution for the separation of alpha and beta chains of hemoglobin because of the introduction of C18 carbon chains, and shows great potential for the separation of bio-macromolecules.