Perfusion chromatography

Novel monolithic poly(phenyl acrylate-co-1,4-phenylene diacrylate) capillary columns for biopolymer chromatography

Monolithic capillary columns were prepared by thermally initiated free radical polymerisation of phenyl acrylate (PA) and 1,4-phenylene diacrylate (PDA) in the confines of 200 microm I.D. fused silica capillaries. Polymerisation was performed in the presence of 2-propanol and tetrahydrofuran (THF) as inert diluents (porogens), using alpha,alpha'-azoisobutyronitrile (AIBN) as initiator. Morphology and porosity of the resulting monoliths were comprehensively studied by scanning electron microscopy (SEM), mercury intrusion porosimetry and inverse size-exclusion chromatography (ISEC). The novel poly(phenyl acrylate-co-1,4-phenylene diacrylate) (PA/PDA) monoliths showed high mechanical stability and were successfully applied to the separation of proteins and oligodeoxynucleotides, employing reversed-phase (RP) and ion-pair reversed-phase (IP-RP) conditions, respectively. Maximum loading capacities for cytochrome c and d(pT)(16) were evaluated and found to be in the region of 200 fmol. Batch-to-batch reproducibility was determined for three independently prepared PA/PDA monolithic capillary columns. Relative standard deviations (RSDs) of retention time (t(R)) of 0.7-1.6% for proteins and 0.2-2.5% for d(pT)(12-18) proved high reproducibility of the PA/PDA supports.

Variation analysis of affinity-membrane model based on Freundlich adsorption

The variation analysis of membrane properties including membrane thickness and pore-size was carried out theoretically by using affinity-membrane model based upon the Freundlich adsorption equation. As the percentage variation of membrane thickness and distribution of pore-size increase, we find that (1) the time of total saturation is delayed; (2) the loading capacity at the point of breakthrough are decreased; (3) solute recovery efficiency and ligand utilization efficiency is decreased; (4) the thickness of unused membrane is increased. The results show that even small variations of thickness and distribution of pore size may severely degrade the membrane performance.

Comparing monolithic and microparticular capillary columns for the separation and analysis of peptide mixtures by liquid chromatography-mass spectrometry

A mixture of ten proteins was trypsinized and injected onto poly-(styrene-divinylben-zene) monolithic columns (60 x 0.20 or 0.10 mm ID) and a column packed with C18 silica particles (75 x 0.075 mm ID), respectively. The columns were eluted at 200-2000 nL/min with gradients of ACN in 0.050% TFA. Eluting peptides were detected by ESI-MS/MS and subsequently identified by database searching. The 100 microm ID monolithic column showed the highest cumulative Mowse scores based on the highest ion scores for the peptides and the largest number of identified peptides. It is shown that the number of identified peptides strongly depends on the dynamic range within the peptide mixture. In consequence, all proteins were identified in a mixture of relatively balanced analyte amounts (12.5-80 fmol) whereas only peptides for six out of ten proteins were found in a sample of high-dynamic range (0.65-270 fmol). The 100 microm monolithic column showed the highest reproducibility for peptide identifications in three consecutive runs. Depending on sample amount, 57-72% of the identified peptides were detectable in each of the three runs of triplicate analyses. The results demonstrate the high suitability of 100 microm monolithic columns for high-resolution peptide separations in proteomic research.

Mathematical analysis of affinity membrane chromatography

A mathematical model including convection, diffusion and Freundlich adsorption is developed. To examine the validity of the model, the affinity membranes were prepared by coating chitosan on the nylon membranes, a ligand of poly-L-lysine was bound to the chitoan-coating membranes, and the adsorption behavior of bilirubin through the stacked affinity membranes was investigated. The agreements between the theoretical and experimental results are exceptional. Using our new model, we show that: (1) As Pe increases, the breakthrough curves become sharper. For Pe greater than 30, the effect of axial diffusion is insignificant; (2) As m increases, the time of total saturation is delayed and the loading capacity at the point of breakthrough is increased; (3) As n decreases, the time of total saturation is delayed and the loading capacity at the point of breakthrough is increased; (4) As r increases, both the time of total saturation and the loading capacity at the point of breakthrough are increased; (5) adsorption rate influences the time of total saturation strongly but contributes little to the loading capacity.

Preparative and analytical chromatography of pegylated myelopoietin using monolithic media

Monolithic media were compared with Q- and SP-Sepharose high performance chromatography for preparative purification and with Q- and SP-5PW chromatography for analysis of a pegylated form of myelopoietin (MPO), an engineered hematopoietic growth factor. The use of either monolithic or Sepharose based supports for preparative chromatography produced highly purified pegylated MPO with the monolithic media demonstrating peak resolution and repeatability at flow rates of 1 and 5 ml/min resulting in run times as much as five-fold shorter compared to Sepharose separations. The monolithic disks also resulted in 10-fold shorter run times for the analytical chromatography, however, their chromatographic profiles and peak symmetry were not as sharp compared to their Q-5PW and SP-5PW counterparts.

Characterization of some physical and chromatographic properties of monolithic poly(styrene–co-divinylbenzene) columns

Monolithic capillary columns were prepared by copolymerization of styrene and divinylbenzene inside a 200 microm i.d. fused silica capillary using a mixture of tetrahydrofuran and decanol as porogen. Important chromatographic features of the synthesized columns were characterized and critically compared to the properties of columns packed with micropellicular, octadecylated poly(styrene-co-divinylbenzene) (PS-DVB-C18) particles. The permeability of a 60 mm long monolithic column was slightly higher than that of an equally dimensioned column packed with PS-DVB-C18 beads and was invariant up to at least 250 bar column inlet pressure, indicating the high-pressure stability of the monolithic columns. Interestingly, monolithic columns showed a 3.6 times better separation efficiency for oligonucleotides than granular columns. To study differences of the molecular diffusion processes between granular and monolithic columns, Van Deemter plots were measured. Due to the favorable pore structure of monolithic columns all kind of diffusional band broadening was reduced two to five times. Using inverse size-exclusion chromatography a total porosity of 70% was determined, which consisted of internodule porosity (20%) and internal porosity (50%). The observed fast mass transfer and the resulting high separation efficiency suggested that the surface of the monolithic stationary phase is rather rough and does not feature real pores accessible to macromolecular analytes such as polypeptides or oligonucleotides. The maximum analytical loading capacity of monolithic columns for oligonucleotides was found to be in the region of 500 fmol, which compared well to the loading capacity of the granular columns. Batch-to-batch reproducibility proved to be better with granular stationary phases compared to monolithic stationary phase, in which each column bed is the result of a unique column preparation process.

Novel general expressions that describe the behavior of the height equivalent of a theoretical plate in chromatographic systems involving electrically-driven and pressure-driven flows

Novel general expressions are constructed and presented that describe the behavior of the height equivalent of a theoretical plate (plate height), H, as a function of the linear velocity, Vx, along the axis, x, of the column and the kinetic parameters that characterize the mass transfer and adsorption mechanisms in chromatographic columns. Open tube capillaries as well as columns packed with either non-porous or porous particles are studied. The porous particles could have unimodal or bimodal pore-size distributions and intraparticle convective fluid flow and pore diffusion are considered. The expressions for the plate height, H, presented in this work could be applicable to high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) systems, and could be used together with experimental plate height, H, versus linear velocity, Vx, data to determine the values of the parameters that characterize intraparticle convective fluid flow and pore diffusion. Furthermore, chromatographic systems under unretained as well as under retained conditions are examined. The experimental values of the plate height, H, versus the linear velocity, Vx, for a CEC system involving charged porous silica C8 particles and an uncharged analyte are compared with the theoretical results for the plate height, H, obtained from the expressions presented in this work. The agreement between theory and experiment is good, and the results indicate that the magnitude of the intraparticle electroosmotic flow (EOF) in the pores of the particles is substantial while the pore diffusion coefficient was of small magnitude. But the overall intraparticle mass transfer resistance in these particles was low because of the significant contribution of the intraparticle EOF. Simulation results are also presented (i) for a hybrid HPLC-CEC system, and (ii) for different CEC systems involving open capillaries as well as packed columns having non-porous or porous particles. The analysis of the results indicates (a) the reasons for the superior performance exhibited by the hybrid HPLC-CEC system over the performance obtained when the system is operated only in the HPLC mode, and (b) the operational configuration and the properties that the structure of the porous particles would have to have in CEC systems involving uncharged or charged analytes under unretained or retained conditions in order to obtain high CEC efficiency (low values of the plate height, H).

Mathematical analysis of frontal affinity chromatography in particle and membrane configurations

The scaleup and optimization of large-scale affinity-chromatographic operations in the recovery, separation and purification of biochemical components is of major industrial importance. The development of mathematical models to describe affinity-chromatographic processes, and the use of these models in computer programs to predict column performance is an engineering approach that can help to attain these bioprocess engineering tasks successfully. Most affinity-chromatographic separations are operated in the frontal mode, using fixed-bed columns. Purely diffusive and perfusion particles and membrane-based affinity chromatography are among the main commercially available technologies for these separations. For a particular application, a basic understanding of the main similarities and differences between particle and membrane frontal affinity chromatography and how these characteristics are reflected in the transport models is of fundamental relevance. This review presents the basic theoretical considerations used in the development of particle and membrane affinity chromatography models that can be applied in the design and operation of large-scale affinity separations in fixed-bed columns. A transport model for column affinity chromatography that considers column dispersion, particle internal convection, external film resistance, finite kinetic rate, plus macropore and micropore resistances is analyzed as a framework for exploring further the mathematical analysis. Such models provide a general realistic description of almost all practical systems. Specific mathematical models that take into account geometric considerations and transport effects have been developed for both particle and membrane affinity chromatography systems. Some of the most common simplified models, based on linear driving-force (LDF) and equilibrium assumptions, are emphasized. Analytical solutions of the corresponding simplified dimensionless affinity models are presented. Particular methods for estimating the parameters that characterize the mass-transfer and adsorption mechanisms in affinity systems are described.

New synthetic ways for the preparation of high-performance liquid chromatography supports

The latest developments and in particular important synthetic aspects for the preparation of modern HPLC supports are reviewed. In this context, the chemistry of inorganic supports based on silica, zirconia, titania or aluminum oxide as well as of organic supports based on poly(styrene-divinylbenzene), acrylates, methacrylates and other, more specialized polymers is covered. Special consideration is given to modern approaches such as sol-gel technology, molecular imprinting, perfusion chromatography, the preparation of monolithic separation media as well as to organic HPLC supports prepared by new polymer technologies such as ring-opening metathesis polymerization. Synthetic particularities relevant for the corresponding applications are outlined.

High-performance liquid chromatography-electrospray ionization mass spectrometry of single- and double-stranded nucleic acids using monolithic capillary columns

Monolithic capillary columns were prepared by copolymerization of styrene and divinylbenzene inside a 200-microm i.d. fused silica capillary using a mixture of tetrahydrofuran and decanol as porogen. With gradients of acetonitrile in 100 mM triethylammonium acetate, the synthesized columns allowed the rapid and highly efficient separation of single-stranded oligodeoxynucleotides and double-stranded DNA fragments by ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC). Compared with capillary columns packed with micropellicular, octadecylated poly-(styrene/divinylbenzene) particles, an improvement in column performance of approximately 40% was obtained, enabling the analysis of an 18-mer oligodeoxynucleotide with a column efficiency of more than 190000 plates per meter. The chromatographic separation system was on-line-coupled to electrospray ionization mass spectrometry (ESI-MS). To improve the mass spectrometric detectabilities, 25 mM triethylammonium bicarbonate was utilized as an ion-pair reagent at the cost of only little reduction in separation performance and acetonitrile was added postcolumn as the sheath liquid through the triaxial electrospray probe. High-quality mass spectra of femtomole amounts of 3-mer to 80-mer oligodeoxynucleotides were recorded showing very little cation adduction. Double-stranded DNA fragments ranging in size from 51 to 587 base pairs were separated and detected by IP-RP-HPLC-ESI-MS. Accurate mass determination by deconvolution of the mass spectra was feasible for DNA fragments up to the 267-mer with a molecular mass of 165 019, whereas the spectra of longer fragments were too complex for deconvolution because of incomplete separation due to overloading of the column. Finally, on-line IP-RP-HPLC tandem MS was applied to the sequencing of short oligodeoxynucleotides.

Perfusion chromatography: an emergent technique for the analysis of food proteins

Perfusion chromatography is a technique arised to overcome the problem associated with mass transfer in the separation of large molecules such as proteins by high-performance liquid chromatography (HPLC). Perfusion media are constituted by two set of pores: throughpores (6000-8000 A) and diffusive pores (800-1500 A) which enable better access of macromolecules to the inner of the particle by the combination of convective and diffusive flow. As a consequence, times required for a chromatographic separation are reduced. Perfusion media are available in different chromatographic modes: reversed-phase, ion-exchange, hydrophobic interaction, and affinity. From the theoretical models developed to explain the dynamic of retention of solutes in perfusive supports, it was derived that efficiency of a separation was independent of the flow-rate and only depended slightly on the particle diameter. Furthermore, loading capacity was also independent of the superficial velocity. All these advantages have promoted the use of this chromatographic technique for the separation of biomolecules both in analytical and preparative chromatography. Characteristics of perfusion chromatography make this technique very interesting for the analysis of food proteins. Perfusion chromatography enables the assessment of protein composition of a foodstuff at sufficient speed and low cost to be suitable in routine analysis.

Modeling and simulation of the dynamic behavior of monoliths. Effects of pore structure from pore network model analysis and comparison with columns packed with porous spherical particles

A mathematical model is presented that could be used to describe the dynamic behavior, scale-up, and design of monoliths involving the adsorption of a solute of interest. The value of the pore diffusivity of the solute in the pores of the skeletons of the monolith is determined in an a priori manner by employing the pore network modeling theory of Meyers and Liapis [J. Chromatogr. A, 827 (1998) 197 and 852 (1999) 3]. The results clearly show that the pore diffusion coefficient, Dmp, of the solute depends on both the pore size distribution and the pore connectivity, nT, of the pores in the skeletons. It is shown that, for a given type of monolith, the film mass transfer coefficient, Kf, of the solute in the monolith could be determined from experiments based on Eq. (3) which was derived by Liapis [Math. Modelling Sci. Comput., 1 (1993) 397] from the fundamental physics. The mathematical model presented in this work is numerically solved in order to study the dynamic behavior of the adsorption of bovine serum albumin (BSA) in a monolith having skeletons of radius r(o) = 0.75x10(-6) m and through-pores having diameters of 1.5x10(-6)-1.8x10(-6) m [H. Minakuchi et al., J. Chromatogr. A, 762 (1997) 135]. The breakthrough curves of the BSA obtained from the monolith were steeper than those from columns packed with porous spherical particles whose radii ranged from 2.50x10(-6) m to 15.00x10(-6) m. Furthermore, and most importantly, the dynamic adsorptive capacity of the monolith was always greater than that of the packed beds for all values of the superficial fluid velocity, Vtp. The results of this work indicate that since in monoliths the size of through-pores could be controlled independently from the size of the skeletons, then if one could construct monolith structures having (a) relatively large through-pores with high through-pore connectivity that can provide high flow-rates at low pressure drops and (b) small-sized skeletons with mesopores having an appropriate pore size distribution (mesopores having diameters that are relatively large when compared with the diameter of the diffusing solute) and high pore connectivity, nT, the following positive results, which are necessary for obtaining efficient separations, could be realized: (i) the value of the pore diffusion coefficient, Dmp, of the solute would be large, (ii) the diffusion path length in the skeletons would be short, (iii) the diffusion velocity, vD, would be high, and (iv) the diffusional response time, t(drt), would be small. Monoliths with such pore structures could provide more efficient separations with respect to (a) dynamic adsorptive capacity and (b) required pressure drop for a given flow-rate, than columns packed with porous particles.

Network modeling of the convective flow and diffusion of molecules adsorbing in monoliths and in porous particles packed in a chromatographic column

A cubic lattice network of interconnected pores was constructed to represent the porous structure existing in a monolith (continuous bed) or in a column packed with porous chromatographic particles. Expressions were also constructed and utilized to simulate, through the use of the pore network model, the intraparticle interstitial velocity and pore diffusivity of adsorbate molecules in porous chromatographic particles or in monoliths under retained and unretained conditions. The combined effects of steric hindrance at the entrance to the pores and frictional resistance within the pores, as well as the effects of pore size, pore connectivity, nT, of the porous network, molecular size of adsorbate and ligand (active site), and the fractional saturation of adsorption sites (ligands), have been considered. The results for the adsorption systems studied in this work, indicate that the obstruction effects on the intraparticle interstitial velocity, due to (a) the thickness of the immobilized layer of active sites and (b) the thickness of the adsorbed layer, are small and appear to be insignificant when they are compared with the very significant effect that the value of the pore connectivity, nT, has on the magnitude of the intraparticle interstitial velocity. The effective pore diffusion coefficient of the adsorbate molecules was found to decline with increasing molecular size of ligand, with increasing fractional saturation of the active sites or with diminishing pore size, and with decreasing pore connectivity, nT. The results also show that the magnitude of the interstitial fluid velocity is many times larger than the diffusion velocity of the adsorbate molecules within the porous adsorbent particles. Furthermore, the results clearly show that the intraparticle interstitial velocity and the pore diffusivity of the adsorbate increase significantly as the value of the pore connectivity, nT, of the porous medium increases. The results of this work indicate that the pore network model and the expressions presented in this work, could allow one, for a given porous adsorbent, adsorbate, ligand (active site), and interstitial column fluid velocity, to determine in an a priori manner the values of the intraparticle interstitial velocity and pore diffusivity within the monolith or within the porous adsorbent particles as the fractional saturation of the active sites changes. The values of these transport parameters could then be employed in the macroscopic models that could predict the dynamic behavior, scale-up, and design of chromatographic systems. The theoretical results could also have important implications in the selection of a ligand as well as in the selection and construction of an affinity porous matrix.

Characterization of large-pore polymeric supports for use in perfusion biochromatography

Perfusion chromatography is uniquely characterized by the flow of a portion of the column eluent directly through the resin in the packed bed. The benefits of this phenomenon and some of the properties of perfusive resins have been described before, and can be summarized as enhanced mass transport to interior binding sites. Here we extend the understanding of this phenomenon by comparing resins with different pore size distributions. Resins are chosen to give approximately the same specific pore volumes (as shown in the characterization section) but the varying contribution of large pores is used to control the amount of liquid flowing through the beads. POROS R1 has the largest contribution of throughpores, and therefore the greatest intraparticle flow. POROS R2 has a lower contribution of throughpores, and a higher surface area coming from a greater population of diffusive pores, but still shows significant mass transport enhancements relative to a purely diffusive control. Oligo R3 is dominated by a high population of diffusive pores, and is used comparatively as a non-perfusive resin. Although the pore size distribution can be engineered to control mass transport rates, the resulting surface area is not the only means by which binding capacity can be controlled. Surface coatings are employed to increase binding capacity without fundamentally altering the mass transport properties. Models are used to describe the amount of flow transecting the beads, and comparisons of coated resins to uncoated (polystyrene) resins leads to the conclusion that these coatings do not obstruct the throughpore structures. This is an important conclusion since the binding capacity of the coated product, in some cases, is shown to be over 10-fold higher than the precursor polystyrene scaffold (i.e., POROS R1 or POROS R2).

Comparison of diffusion and diffusion-convection matrices for use in ion-exchange separations of proteins

A comprehensive study has been undertaken to characterise a range of chromatographic properties for a series of modified polystyrene-divinylbenzene (PS-DVB) chromatography matrices. The matrices studied included diffusion matrices and matrices that allowed convective mass transfer of liquid into the particles at high flow-rates, so-called "perfusion" matrices. The matrices tested included the following: CG1000sd 20-50 microns (TosoHaas), PLRP4000s 15-25 microns, 50-70 microns (Polymer Labs.), Source 15RPC and 30RPC, 15S, 30S, (Pharmacia Biotech), POROS 20SP type 1 matrix and OH activated POROS 20 type 2 matrix (PerSeptive Biosystems) and SP Sepharose Fast Flow (Pharmacia Biotech). A Van Deemter equation was used to determine bead tortuosities and split ratios. Frontal analysis, resolution studies, ionic capacities and isotherms were measured. It was found that diffusion-convection chromatographic particles had smaller plate heights to comparable diffusion particles. The smallest diffusion bead, Source 15, had the lowest plate heights at low superficial velocities, but the small particle size resulted in a high back pressure at high flow-rates. The equilibrium binding capacities for lysozyme and IgG on the diffusion-convection matrices were substantially lower than the equilibrium binding capacities on the diffusion matrices. The dynamic capacities for these proteins were also lower on the diffusion-convection particles, compared to the diffusion particles, over the tested flow-rates. At high protein loading, resolution between proteins was higher on diffusion particles than on diffusion-convection particles. Diffusion-convection particles showed low or no resolution at high protein loading. At analytical level loadings, the diffusion-convection particles achieved a high resolution over the whole flow-rate range tested and were more suitable for this application than diffusion particles.

Frontal chromatography of proteins. Effect of axial dispersion on column performance

A mathematical model describing the dynamic adsorption of proteins in columns packed with spherical porous adsorbent particles is used to study the effect of axial dispersion on the performance of chromatographic systems. The values of the axial dispersion coefficient, DL, are estimated from a correlation based on a model describing axial dispersion in packed beds that provides satisfactory results when compared with experiment. Simulations of frontal chromatography in systems including axial dispersion and in systems without axial dispersion are made and compared to determine the effect of axial dispersion on the efficiency of the adsorption process; also, the system parameters that influence axial dispersion are examined. It is found that the reduction in the efficiency of the adsorption process due to axial dispersion is small (< 1%) for columns of length 10 cm or greater. However, for short columns, this efficiency reduction can be as large as 10%. Increasing the adsorbent particle diameter, dp, increases the magnitude of the reduction in efficiency due to axial dispersion; the effect of increasing the adsorbent particle diameter, dp, is much more pronounced in a short column than in a long column.

Permeable packings and perfusion chromatography in protein separation

The use of permeable packings in perfusion chromatography for protein separation is reviewed. Mass transport mechanisms in large-pore materials include forced convection in addition to diffusive transport. The key concept in perfusion chromatography is the "augmented" diffusivity by convection which explains the improved efficiency of perfusive packings compared with conventional supports. An extended Van Deemter equation has to be applied when calculating the height equivalent to a theoretical plate (HETP) of chromatographic columns with flow-through particles. It is shown that the effect of forced convective flow in pores is to drive the separation performance between diffusion-controlled and equilibrium limits. A methodology to understand mass transfer mechanisms in permeable packings is proposed. Experimental results for protein separation by high-performance liquid chromatography in new packing media are discussed. Simulated moving bed technology is addressed.

Model discrimination and estimation of the intraparticle mass transfer parameters for the adsorption of bovine serum albumin onto porous adsorbent particles by the use of experimental frontal analysis data

Experimental data from a chromatographic system involving the adsorption of bovine serum albumin (BSA) onto porous anion-exchange adsorbent particles packed in a column are presented. The parameters that characterize the mass transfer mechanisms of intraparticle diffusion and convection are estimated by fitting the predictions of dynamic mathematical models describing adsorption in column systems having spherical perfusive and purely diffusive adsorbent particles to the experimental breakthrough data obtained from the column adsorption system. Both linear and nonlinear expressions for the equilibrium isotherm are considered. The values of the transport parameters are estimated in the time domain for the nonlinear adsorption models and in the Laplace transform domain for the linear adsorption models. The capabilities of the different models to describe satisfactorily the dynamic behavior of the adsorption system are compared. The dynamic nonlinear adsorption model for purely diffusive particles is found to describe most appropriately the dynamic behavior of the experimental chromatographic system studied in this work.

Perfusion liquid chromatography of whey proteins

A perfusion reversed-phase (RP) HPLC method was developed for the rapid separation of the main bovine whey proteins: alpha-lactalbumin (alpha-LA), serum albumin (BSA) and the genetic variants of beta-lactoglobulin (A and B) (beta-LG A and beta-LG B). For the method development, the influence of factors favouring structural changes of proteins (temperature and organic acid concentration in the mobile phase), gradient and other chromatographic conditions and the mass of protein injected was examined. The optimized method allowed the separation of proteins in about 1.5 min (cycle time 3.5 min) with resolution around 1.0 for the beta-lactoglobulins. The method was applied to the determination of proteins in a whey from raw bovine milk. The precision of the determinations was < or = 3.75 mg per 100 ml (S.D.). With respect to the accuracy, errors < or = 7.0% in the determination of alpha-LA, beta-LG A and beta-LG B were obtained, compared with an RP-HPLC reference method. However, higher errors in the quantification of BSA were found owing to the lack of purity of the peak assigned. In addition, the proposed method has proved to be very useful in the detection of homologous whey proteins from different species (cow, sheep and goat) in milk mixtures.

Modified poly(glycidyl methacrylate-co-ethylene dimethacrylate) continuous rod columns for preparative-scale ion-exchange chromatography of proteins

A continuous rod of porous poly(glycidyl methacrylate-co-ethylene dimethacrylate) has been prepared by a free radical polymerization within the confines of a 300 x 8 mm I.D. chromatographic column. The epoxide groups of the rod have been modified by a reaction with diethylamine that affords ionizable functionalities required for the ion-exchange chromatographic mode. The properties of this rod column have been characterized and the column has been used successfully for the chromatographic separation of proteins. The column exhibits a dynamic capacity that exceeds 300 mg at a flow velocity of 200 cm/min. An excellent selectivity allows the separation of up to 300 mg of a protein mixture in a single run.