Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/281—Sorbents specially adapted for preparative, analytical or investigative chromatography
  • B01J20/286—Phases chemically bonded to a substrate, e.g. to silica or to polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
  • B01J20/3202—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
  • B01J20/3204—Inorganic carriers, supports or substrates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
  • B01J20/3202—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
  • B01J20/3206—Organic carriers, supports or substrates
  • B01J20/3208—Polymeric carriers, supports or substrates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
  • B01J20/3214—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the method for obtaining this coating or impregnating
  • B01J20/3217—Resulting in a chemical bond between the coating or impregnating layer and the carrier, support or substrate, e.g. a covalent bond
  • B01J20/3219—Resulting in a chemical bond between the coating or impregnating layer and the carrier, support or substrate, e.g. a covalent bond involving a particular spacer or linking group, e.g. for attaching an active group
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
  • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
  • B01J20/3242—Layers with a functional group, e.g. an affinity material, a ligand, a reactant or a complexing group
  • B01J20/3268—Macromolecular compounds
  • B01J20/3278—Polymers being grafted on the carrier
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
  • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
  • B01J20/3242—Layers with a functional group, e.g. an affinity material, a ligand, a reactant or a complexing group
  • B01J20/3268—Macromolecular compounds
  • B01J20/328—Polymers on the carrier being further modified
  • B01J20/3282—Crosslinked polymers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/416—Systems
  • G01N27/447—Systems using electrophoresis
  • G01N27/44704—Details; Accessories
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/416—Systems
  • G01N27/447—Systems using electrophoresis
  • G01N27/44704—Details; Accessories
  • G01N27/44752—Controlling the zeta potential, e.g. by wall coatings

Definitions

• CE Capillary Electrophoresis
• silica dissolves at extreme pH's, which is another limitation of this approach.
• 3 Other approaches in addressing the above problem involve adding compounds 4"6 that compete with the analytes for interaction sites on the capillary wall. These additives, however, may adversely affect the separation of analytes.
• coatings are formed by reacting silanes that have appropriate reactive end groups with reactive end groups on prederivatized polymers. These coatings were disclosed by Berlin et al. 11 to minimize or reduce EO flow. They discussed several synthetic procedures for creating various derivatives of dextran n and PEG 13 and their utility in several applications iOncluding modifying control pore glass beads. However, data on the pH stability of this coating and its performance with proteins as test analytes were not shown. Following a similar approach, Hjerten and Kubo I4 showed the attachment of several polymers (e.g., methylcellulose and dextran) after a prederivatization step. The prederivatization step was required prior to attaching the polymers to the methacryl silane treated capillary. Additionally, the polymer coupling process was dependent upon a high yield of the prederivatization reaction.
• polymers e.g., methylcellulose and dextran
• Malik et al. 15,16 adapted a GC-type static coating procedure, in which the coating was achieved by depositing a mixture of polymer, initiators, and silane reagent on the surface of a capillary by using a low boiling point solvent. The capillary was then heat treated to cross-link the surface film.
• the coating thickness influenced the EO flow and performance and required optimization.
• variabilities in efficiencies were observed between analytes in a Superox-4 coated capillary and between two Superox-4 coated capillaries.
• two Ucon 75-H-90000 polymer coated capillaries tested under identical conditions gave different migration times and mobilities, indicating problems with the reproducibility of the coating process.
• polymer based support surfaces have been used for separating the components in a fluid stream such as for capillary electrophoresis or liquid chromatography.
• Such polymeric support surfaces can be on the inner walls of the conduit (e.g. capillary), or can form a packing of polymeric particles for liquid chromatography.
• such polymeric support surfaces do not have the desired properties for separating components.
• such surfaces have been modified by coating with suitable hydrophilic polymers as disclosed in Afeyan et al. (5,503,933).
• An object of the invention is to provide a cross-linked coating of preformed polymer directly or indirectly covalently linked to the surface of the support.
• an intermediate coupling agent is used between the support surface and the preformed polymer while, in the other embodiment, it is not.
• a solid support has a coating on its surface which alters the properties of the support surface for separating components in a fluid stream in contact therewith.
• the coating comprises a coupling agent including a functional group and is covalently bound to said support surface in a substantially uniform layer, and a preformed polymer comprising totally saturated, substituted or unsubstituted, carbon chain backbones from which leaving groups have been abstracted while in solution and in contact with said coupling agent layer to form bonding sites on said preformed polymer which covalently bind to said coupling agent and which crosslink said preformed polymer forming a coating comprising a three-dimensional, cross-linked polymer network on said solid support.
• the invention also includes a method of coating the solid support surface which alters the properties of the support surface for separating components in a fluid stream.
• the method comprises (a) covalently binding a coupling agent (including functional groups capable of forming free radical sites under hydrogen abstraction conditions) to said support surface in a uniform layer, and (b) thereafter, contacting said covalently bound coupling agent with a solution of said preformed polymer comprising totally saturated, substituted or unsubstituted, carbon chain backbones including leaving groups, under hydrogen abstraction conditions of elevated temperature in the presence of a free radical catalyst, said support surface not being soluble in said polymer, to remove leaving groups from said preformed polymer carbon chains to form free radical carbon binding sites which covalently bond to said coupling agent layer and to crosslink at least some of said preformed polymer through thus-formed free radical carbon binding sites therein to form a dimensional polymer network coating on said solid support surface.
• a coupling agent including functional groups capable of forming free radical sites under hydrogen abstraction conditions
• the second functional group in the coupling agent is typically a carbon moiety bound to a leaving group such as a reactive group (e.g. a halogen) or hydrogen.
• the leaving group is capable of being abstracted to a free radical under hydrogen abstraction conditions.
• the reactive groups or hydrogen may be terminal groups or interior of the carbon chain.
• one preferred support surface comprises silica with a coupling agent comprising a silane.
• Preferred leaving groups are hydrogen or halogens.
• the solid support preferably is either the inner wall of a capillary for capillary electrophoresis or the packing of a flow-through particle bed such as one used for liquid chromatography.
• no intermediate coupling agent is used for coating an organic polymeric solid support which has saturated or unsaturated carbon chains including functional groups capable of forming free radical sites under hydrogen abstraction conditions to alter the properties of separating components in a fluid stream in contact therewith.
• the coating comprises preformed polymer including totally saturated substituted or unsubstituted carbon chain backbones from which leaving groups have been abstracted while in solution and in contact with said support surface to form free radical binding sites on said preformed polymer and covalently bound to free radical binding sites formed on said support surface functional groups, and to crosslink said preformed polymer forming a coating comprising a three-dimensional, cross-linked polymer network on said solid support.
• One preferred method for coating the polymeric solid support surface comprises contacting said support surface with preformed polymer comprising totally saturated carbon chain backbones including leaving groups under hydrogen abstraction conditions of elevated temperature in the presence of a free radical catalyst, to abstract hydrogen or other leaving groups from said preformed polymer carbon chains to form abstracted carbon sites which covalently bond said support surface to carbon chains, and to crosslink at least some of said preformed polymer through free radicals created at said hydrogen extraction carbon sites therein to form a three-dimensional polymer network coating on said solid support surface.
• Figure 1 are electropherograms showing separations of basic proteins using various polymer coated capillaries.
• Figure 2 is a reproducibility study using a MET-PVP (360K) coated capillary.
• Figure 3 is a series of graphs slowing the effect of polymer molecular weight and concentration on efficiency of basic proteins.
• Figure 4 is a electropherogram illustrating acidic protein separations using a cationic polymer coated capillary.
• Figure 5 is a electropherogram illustrating separation of test anions using a cationic polymer coated capillary.
• Figure 6 is a electropherogram illustrating separation of proteins from 2% Vitamin D Milk using a MET-PVP coated capillary.
• Figure 7 is a electropherogram illustrating separation of hemoglobin variants using a MET-PVP coated capillary.
• the invention is directed to modifying the properties of a solid support surface for separating components in a fluid stream in contact with such surface.
• the support surface comprises the inner wall of a conduit such as a capillary for capillary electrophoresis or capillary electrochromatography or capillary liquid chromatography or supercritical fluid chromatography or gas chromatography.
• the solid support surface comprises the particulate packing of a flow-through particle bed used for liquid chromatography or capillary electrochromatography or supercritical fluid chromatography or gas chromatography.
• Other type of solid support surfaces useful in electrophoresis which could be modified according to the invention include silica or glass based microfabricated capillary array systems and slab-gel systems.
• the invention will first be described with respect to the embodiment in which a coupling agent is used and in which the solid support surface is the inner wall of a capillary for capillary electrophoresis.
• the coupling agent mode could be used for other solid surfaces as described above.
• a wide variety of solid support surfaces can be used so long as they are capable of covalent binding to a coupling agent which in turn is capable of covalent binding to a preformed polymer under hydrogen abstraction conditions.
• a common material used for the capillary in capillary electrophoresis is fused silica.
• Suitable support surfaces it contains hydroxyl groups which are readily coupled to preferred coupling agents such as silanes.
• Suitable inorganic solid support surfaces containing hydroxyl groups, or groups convertible to hydroxyl groups include silica, titania, quartz, glass, alumina, thoria, beryllia and zirconia.
• Suitable coupling agents are ones which are capable of covalent binding to such support surfaces and, in turn, of covalent binding to the preformed polymer under hydrogen abstraction conditions as described below.
• Mechanisms of attachment of coupling agents to common support surfaces such as silica are well known such as illustrated in Hjerten patent 4,680,201.
• These coupling agents typically are bifunctional compounds with a first functional group capable of covalent attachment to the solid support surface and a second functional group (in the form of a leaving group) capable of binding to the preformed polymer.
• Suitable coupling agent first functional groups capable of binding the solid support include mono, di and tri alkoxy groups such as methoxy and ethoxy groups and halogens such as chlorine.
• the coupling agent still includes a second functional group capable of forming a free radical binding site which covalently binding the preformed polymer.
• second functional group could be a saturated carbon chain in which the bound hydrogen is a leaving group.
• the second functional group could be a leaving group such as hydrogen or a halogen.
• second functional groups capable of binding the preformed polymer under hydrogen abstraction conditions are termed "second functional groups”.
• the preformed polymer in solution also forms a free radical binding site in contact with the coupling agent free radical binding site to form a covalent bonding between the coupling agent layer and the preformed polymer.
• Important labile hydrogen groups include protons on the carbonyl functions of aldehydes and formate esters, on the carbinol functions of primary or secondary alcohols, on the -carbon atoms of amines and ethers, on the thiol functions of mercaptans and on carbon atoms adjacent to unsaturated functions. Abstraction of leaving group abstraction follows the order of strength of the bonds being broken, except for abstraction of hydrogen:
• Chlorine, bromine and iodine are very labile (e.g. in polyhalomethanes and other haloalkanes).
• Suitable silanes in general can be designated as R ⁇ SiX ⁇ .
• the X group reacts with the substrate and this results in a covalent bond between the substrate and the silane.
• X is a hydrolyzable group and includes mono, di or tri substituted alkoxy such as methoxy or ethoxy, or halogen groups such as chlorine.
• the R group consists of a non-hydrolyzable organic chain which includes end-group functionalities such as acetoxy or acryloxy or allyl or amino or alkyl or benzyl, or vinyl groups. R may also includes other suitable functionalities such as halo or cyano or thiocyano or mercapto groups.
• Suitable silanes are listed in 1) Silicon Compounds: Register & Review, from United Chemical Technologies, 5th Ed.,
• the coating process described herein requires no reactive functionalities for coupling, either on the polymer or on the silane. Free radical sites formed on both the polymer and the silane are sufficient for simultaneous coupling and cross-linking. No special conditions are required for this coupling reaction.
• the capillaries coated by the above process satisfy the four major requirements of a coated capillary for CE; namely: (1) provide reproducible separation of analytes through generation of reproducible EO flow; (2) allow minimal interaction with the analytes, thus maximizing efficiency of the separation and recovery, (3) show minimal absorbance at the monitored wavelength for enhanced sensitivity, and (4) retain stable performance under a variety of buffer and pH conditions for robust operation.
• silane coupling agent bound to a silica solid support surface forms Si-O-Si linkages.
• coupling agents other than silanes may be employed to provide different coupling linkages.
• an allyl methacrylate coupling agent may be bound to a silica surface by Si-C linkage 17 .
• Analogous linkages are formed between silanes and hydroxyl-containing solid support surfaces other than silica (e.g. Ti-O-Si) (Matyska et al., in Poster #P-0561, 20th International Symposium of High Performance Liquid Phase Separations and Related Techniques, June 1996, San Francisco, CA).
• silica e.g. Ti-O-Si
• the preformed polymer of the present invention is coupled to the free radical sites formed at least in part by removal of leaving groups in the preformed polymer backbone under hydrogen abstraction conditions.
• the same principles apply to selection of suitable leaving groups for the coupling agent as for the preformed polymer.
• the preformed polymer is formed of totally saturated carbon chain backbones which have not been prederivatized to form unsaturation prior to covalent bonding with a coupling agent.
• the preformed polymer may include unsaturation in carbon side chains or moieties, such as aromatic groups, including benzene rings, e.g. in polystyrene.
• the carbon chain backbones typically include from 50 to 10,000 carbons in the chains. They may be of any suitable length to provide the desired property so long as they include leaving groups which are abstracted under hydrogen abstraction conditions to form covalent bonds with the coupling agent which has previously been covalently bound to the support surface.
• the coupling agent binds in a substantially uniform layer to the support surface. That is, it substantially covers the support surface by interacting with the available reactive sites on such surface when it is uniformly available as the inner wall of a capillary. If the surface is irregular such as the pores of a macroporous surface, there would be corresponding irregularity in the uniformity of the coating.
• the carbon chains, typically polymerized, of the preformed polymer may be unsubstituted, i.e. include only hydrogen groups along the chain which are abstractable under hydrogen abstraction condition to form free radical sites.
• the carbon chains may be substituted by a variety of groups or moieties which can serve different purposes.
• the group may comprise leaving groups (e.g. halogen) which are abstracted to form the free radical bonding sites for bonding to the coupling agent and for cross-linking.
• Other substituted leaving groups include hydrogen bound to sulfur as in mercapto "SH" groups typically at the end of the chain.
• the substitution may comprise non-leaving groups which serves the function of altering the properties of the support surface for separating the components in the fluid stream. For example, a quaternary nitrogen atom imparts ion exchange selectivity to the support surface after it is bound. Similarly, an OH group imparts hydrophilicity to the support surface after it is bound.
• a suitable list of preformed polymers which include appropriate leaving groups and also the ability to alter characteristics include substituted or unsubstituted polyalkylenes, polyesters, polyamines, polyamindes, polyethers, polysufonates, polyoxides, polyalkyleneglycols, polystyrenic based polymers, polyacetals, polychlorides, polysaccharides, polycarbonates, polymers of monoethylenically unsaturated monomers, polymers of polyvinylidene monomers and mixtures and copolymers of the above polymers.
• Preferred suitable specific preformed polymers include polyethyleneoxide, polyacrylamide, polyvinylalcohol, polyvinylpyrolidone, polyethyleneglycol, acrylamidomethylpropylsulfonic acid, polyacrylic acid and methacrylamidopropyltrimethylammonium chloride.
• Other characteristics of the preformed organic polymer are that they be sufficiently soluble in solvent to uniformly coat the solid support surface without dissolving the solid support.
• Suitable solvents include water, alcohols such as methanol, ethanol, polyols such as glycerine, ethylene glycol, ketone-alcohols such as diacetone alcohol, acids such as formic acid, acetic acid, ether-alcohols such as glycol ethers, lactones such as ⁇ -butryolactone, esters such as ethyl lactate, ethyl acetate, ketones such as methylcyclohexanone, acetone, chlorinated hydrocarbons such as methylene dichloride, chloroform, carbon tetrachloride, lactams such as 2-pyrolidone, N-methyl-2-pyrolidone, amines such as butylamine, cyclohexylamine, aniline, morpholine, nitroparaffms such as nitromethanes, hydrocarbons such as benzene, toluene, hexane, alone or in combination with other solvents, ether
• the separation characteristic of the coating can be used in a wide variety of applications. For example, it could be used in capillary electrophoresis in which the coating can vary EO flow.
• the coating can be anionic, cationic or neutral, depending on the desired effect.
• the coating substantially covers the solid surface. It covalently bonds in a cross-linked three-dimensional matrix between preformed polymer chains and with the coupling agent.
• This cross-linked coating is highly stable. It is stable over a wide pH range (e.g. 2 to 10) due to its high level of cross-linking on the surface.
• the extent of substitution on the polymer chain and on the coupling agent (e.g. silane) together with type of solvent and initiator system, 22 determines the extent of cross-linking and coupling.
• the coupling agent is first covalently bonded to the support surface as described above. Thereafter, the preformed polymer is dissolved in a suitable solvent in which it is soluble. However, the solid support surface remains in a solid form, i.e. it maintains the integrity of its shape, (e.g. at the inner wall of the capillary or particles).
• a suitable solvent in which it is soluble.
• the solid support surface remains in a solid form, i.e. it maintains the integrity of its shape, (e.g. at the inner wall of the capillary or particles).
• the relative solubility characteristics of the support surfaces and preformed polymers are well known.
• Suitable free radical catalysts include ammonium persulfate, hydrogen peroxide, hydrazine and A20 based catalysts.
• Cross-liriking of neutral polymer coatings are formed by cross-linking polymers such as PVP, 23,24 polystyrene or polyvinyl acetate 25 by treating with the above free radical catalyst at elevated temperature.
• the general mechanism of cross-linking with these free radical catalysts includes abstracting hydrogen atoms from the polymer chain by S0 4 " or OH " radicals. 26
• the molecular weight of the preformed polymer may be varied over a wide range so long as it is capable of being dissolved for uniform contact with the support surface. Typical molecular weights may vary from 5,000 to as high as 1,000,000 or more.
• the preformed polymer covalently links to the coupling agent and simultaneously cross-links to form a coating comprising a three-dimensional polymer network on the support structure.
• This cross-linked nature provides high pH stability to the surface coating and inhibits nonspecific interactions of the analyte with the surface.
• Cross-linking occurs in the coating and can be verified from literature on cross-linking of polymers. Experimental verification of cross-linking was done by solution phase experiments where the linear polymer dissolves in normally used solvents whereas the cross-linked polymers does not. High pH stability of this coating compared to linear polymer coating is an indirect verification of cross-linking.
• the hydrogen abstraction conditions according to the present invention are the conditions well known for hydrogen abstraction from polymers. Encyclopedia of Polymer Science and Engineering, John Wiley & Sons, New York, (1990) Vol. 4, p.385; 24,25 .
• the conditions include elevated temperatures for a sufficient holding time in the presence of a free radical catalyst.
• elevated temperatures means a temperature in excess of room temperature, typically from a minimum of 40°C to as high as 150°C.
• the temperature may vary with the labile characteristics of the leaving group in the covalently bound coupling agent and in the preformed polymer, the type of free radical catalyst, and the like.
• the solvent used will either enhance the formation of cross-linking by transferring the low molecular weight radical to the polymer chain or the solvent radical will minimize the formation of cross-links by combining with macro radicals.
• fully formed polymers are coated onto the surface of a fused silica capillary. No additional derivatization of the polymer is required prior to coupling.
• the coating is achieved by polymer macro-radicals formed during the cross-linking process.
• the polymer becomes attached to the surface of a silane treated capillary through the same radical mechanism.
• Cross-linking between the polymer chains and coupling to the silane takes place simultaneously.
• cross-linking occurs through bonding sites created on the preformed polymer carbon backbones.
• additional cross- linking may take place through bonding sites pretreated on the preformed polymer side chains.
• the resulting coating is a highly cross-linked, stable layer on the capillary surface. The pH stability of this coating is improved over existing coatings, due to the high level of cross-linking on the capillary surface.
• cross-linking of polymers such as PVP, 23,24 polystyrene and polyvinylacetate 25 can be achieved by treating the polymer with free radical initiators such as ammonium persulfate, hydrogen peroxide, and hydrazine.
• free radical initiators such as ammonium persulfate, hydrogen peroxide, and hydrazine.
• the general mechanism of cross-linking involves abstracting hydrogen atoms from the polymer chain by S0 4 " or OH radicals 3 . 6
• the macroradicals formed then combine to form cross-links. Competing reactions include dissociation of the polymer chain, in some cases generating some few radical- and vinyl-terminated polymer chains.
• the solvent used will either enhance the formation of cross-links by transferring the low molecular weight radical to the polymer chain, or the solvent radical will minimize the formation of cross-links by combining with macroradicals.
• the coating of the present invention may be formed without a coupling agent.
• the polymeric solid support of the present invention has saturated or unsaturated carbon chains including leaving groups in the polymer backbone or in side chains, including cross-links.
• the above discussion of "carbon chains”, “saturated” or “unsaturated” and “leaving groups” for the preformed polymer apply to the organic polymeric solid support.
• the polymeric support material has the requisite functional groups for covalently bonding directly to the preformed polymer under hydrogen abstraction conditions without the requirement for a separate coupling agent.
• the carbon chains with the functional groups may be present after polymerization of one or more monomers to form a homopolymer or copolymer.
• a suitable copolymer would be the well known copolymer styrene-divinyl benzene used as the resin particles in a packed bed for liquid chromatography.
• the polymer includes the residual unsaturated linkages from divinyl benzene.
• Suitable monopolymers include homopolymers of polyvinylidene monomer.
• Suitable copolymers include copolymer of polyvinylidene monomer and monovinylidene monomer.
• suitable polymeric support particles include polymers with grafted side chains or block copolymers or any other derivatized polymer so long as the polymeric support includes the requisite functional groups at the time of reaction with the preformed polymer.
• Suitable substrates of this type include substrates containing surface hydroxyl groups, for example, copolymers of divinylbenzene, styrene and vinylbenzylchloride, which are base esterified for reacting with preformed polymer.
• a coupling agent may be used to provide possible reactive sites on the organic polymeric support prior to covalent bonding with the preformed polymer.
• Suitable bifunctional coupling agents which bind the organic polymeric support particles to the preformed polymer include acrylic anhydrides, acryloyl chlorides, vinyl benzyl chlorides and the like. Reactants of this type are known to those skilled in the art and are listed in general organic chemistry books such as Advanced
• the polymer is attached through multiple linkages on the surface of the substrate, thus enhancing the pH stability of the coating.
• stringent control of reaction conditions is not required since the polymer is already formed.
• In situ polymerized coatings require stringent control of such variables as oxygen levels and temperature 27 because the polymer has to be created on the surface.
• Capillary preparation The inner wall of the capillary (formed of silica) is first rinsed with 1M NaOH for at least 10 minutes with an applied pressure of 10 psi, followed by deionized water. The capillary is then rinsed with 1% (w/v) acetic acid in water for 2 hours.
• Silanization A 1% solution (v/v) of 3-methacryloxypropyltrimethoxysilane in 1% acetic acid is prepared and the capillary is rinsed with this solution for 1 hour using 10 psi pressure. The capillary is stored in the silane solution for at least 24 hours and then displaced with deionized water.
• Polymer solution preparation A 4% PVP (MW: 360,000) solution in water is prepared. 5 ⁇ l of TEMED and 50 ⁇ l of a 10% ammonium persulfate (w/w) is added to 10 ml of the above polymer solution. The above solution is then pressurized into the silanized capillary by applying 10 psi pressure.
• Polymer bonding step The capillary filled with the polymer solution is placed in an oven with the ends sealed, and baked at 80°C for 18 hours. The capillary is rinsed with deionized water and is ready for testing.
• Example 2 All the steps are identical to Example 1 except the silane was an allyltrimeth- oxysilane.
• Chlorodimethyloctyl silane is coupled to a PVP polymer
• Example 1 All the steps are identical to Example 1 except the preferred polymer is polyacrylamide and is prepared as a 2% solution in water.
• Example 1 All conditions are the same as Example 1 except the polymer is a copolymer of 2% (w/w) acrylamide and 1.8% (w/w) methacrylamidopropyltrimethyl- ammonium chloride.
• silica pretreatment 15 ⁇ m silica particles with 150 A° pore size was obtained from Davisil. 30.15 g of deionized water was added to 4.77 g of the above silica material and dispersed uniformly. 2.23 g of Cone.
• Nitric acid was added and the mixture was heated in an oven for 18 hours at 52° C.
• the material was removed after the heat treatment and washed with deionized water until the pH of the water was measured to be neutral. After removal of water the material redispersed in deionized water to a total weight of 54.14g followed by addition of 0.65 g of acetic acid and 0.5 g of methacryloxypropyltrimethoxy silane reagent. The material was dispersed uniformly and heated in an oven for 18 hours at 52°C.
• silica bonded polymer column is suitable for chromatographic separations of inorganic cations and other macromolecules.
• the above silica bonded polymeric material when packed in capillaries is suitable for electrochromatographic separations of inorganic cations and other macromolecules.
• the resultant polymeric material from above was washed with water followed by 100 mM acetic acid before packing in an analytical column using standard methods and apparatus at 6000 psi for 10 minutes.
• This polymeric column is suitable for chromatographic separations of inorganic cations and other macromolecules.
• the above polymeric material when packed in capillaries is suitable for electrochromatographic separations of inorganic cations and other macromolecules.
• Preforming polymers 0.98 g of methacrylamidopropyltrimethyl-ammonium chloride and 0.98 g of acrylamide (BDH Laboratories, Poole, England) was dissolved in 16.6 g of deionized water and degassed. 0.024 g of VA 086 Azo initiator (Wako Pure Chemical Industries Ltd., Japan) was added to the above monomer mixture and the mixture was placed in an oven at 52°C for 18 hours. The resulting polymer was a copolymer of methacrylamidopropyltrimethyl-ammonium chloride and acrylamide. The above polymer was weighed, followed by precipitation with suitable solvent. The precipitated polymer was then redissolved and reconstituted to the original weight in deionized water.
• silica particle 18 g of pretreated silica from step A in Example 8 was washed with deionized water, acetone and followed by deionized water. The final weight of the silica material was adjusted to 10 g with deionized water. 1 g of polymer solution from step A in Example 10 was added to the silica material in water followed by 0.02 g of VA 086 Azo initiator (Wako Pure Chemical Industries Ltd., Japan) The entire material was dispersed homogeneously and then placed in an oven at 80 °C for 18 hours.
• the resulting polymer bonded material from above was washed with water followed by 100 mM citrate buffer at pH 6.0 before packing in an analytical column using standard methods ant apparatus at 6000 psi for 10 minutes.
• This silica bonded polymer column is suitable for chromatographic separation of inorganic anions and other macromolecules.
• the above polymer bonded silica material when packed in capillaries is also suitable for electrochromatographic separation of inorganic anions and other macromolecules.
• the resultant polymeric material from above was washed with water and 100 mM sodium carbonate at pH 11 before packing in an analytical column using standard methods and apparatus at 6000 psi for 10 minutes.
• This column is a polymeric column suitable for chromatographic separation of inorganic anions and other macromolecules.
• the above polymeric material when packed in capillaries is also suitable for electrochromatographic separation of inorganic anions and other macromolecules.
• Nonionic polymer is attached to silica particles suitable for use as a packing
• the resultant polymeric material from above was washed with water and 100 mM acetic acid before packing in an analytical column using standard methods and apparatus at 6000 psi for 10 minutes.
• This column is a polymeric column suitable for size exclusion separations.
• the above polymeric material is suitable for electrochromatographic separations.
• EXAMPLE 14 Cationic polymer is attached to polymer particles suitable for use as a packing.
• step A Attachment to a polymeric particle: 0.4 g of polymer prepared as shown in step A was added to 5.1 g of water. The above mixture was initiated by adding 0.02 g of Azobiscyanovaleric acid initiator (Fluka Chemicals). 2.3 g of acetic acid is added to above mixture followed by 2.31 g of a dried 55% cross- linked macroporous resin (substrate is ethylvinylbenzene cross-linked with 55% divinylbenzene resin preparation described in U.S. Patent No. 4,224,415) and dispersed. 4.7 g of ammonium hydroxide was added to above slurry and dispersed homogeneously and then placed in an oven at 52° C for 8 hours.
• Azobiscyanovaleric acid initiator Fluoride
• 2.3 g of acetic acid is added to above mixture followed by 2.31 g of a dried 55% cross- linked macroporous resin (substrate is ethylvinylbenz
• the resultant polymeric material from above was washed with 50 ml of deionized water, followed by 200 ml of acetone and followed by 50 ml of a 1 X carbonate/bicarbonate solution (1.8 mM of sodium carbonate + 1.7 mM of sodium hydrogen carbonate) and dispersed in a 10 X carbonate/bicarbonate solution (18 mM sodium carbonate/17 mM sodium hydrogen carbonate) before packing in an analytical column using standard methods and apparatus at 6000 psi for 10 minutes.
• This column is a polymeric column suitable for chromatographic separation of inorganic anions and other macromolecules.
• the above polymeric material when packed in capillaries is also suitable for electrochromatographic separation of inorganic anions and other macromolecules.
• Cationic copolymer is attached to polymeric particles suitable for a use as a packing
• step A Attachment to a polymeric particle: 0.45 g of polymer prepared as shown in step A was added to 5.3 g of water. The above mixture was initiated by adding 0.02 g of Azobiscyanovaleric acid initiator (Fluka Chemicals). 2.37 g of acetic acid is added to above mixture followed by 23 g of a dried 55% cross- linked macroporous resin (resin preparation described in patent 4,224,415) and dispersed. 4.9 g of ammonium hydroxide was added to above slurry and dispersed homogeneously and then placed in an oven at 52° C for 8 hours.
• Azobiscyanovaleric acid initiator Fluorous acid initiator
• acetic acid is added to above mixture followed by 23 g of a dried 55% cross- linked macroporous resin (resin preparation described in patent 4,224,415) and dispersed.
• 4.9 g of ammonium hydroxide was added to above slurry and dispersed homogeneously and then placed in an
• the resultant polymeric material from above was washed with 50 ml of deionized water, followed by 200 ml of acetone and followed by 50 ml of a 1 X carbonate/bicarbonate solution (1.8 mM of sodium carbonate + 1.7 mM of sodium hydrogen carbonate) and dispersed in a 10 X carbonate bicarbonate solution (18 mM sodium carbonate/ 17 mM sodium hydrogen carbonate) before packing in an analytical column using standard methods and apparatus at 6000 psi for 10 minutes.
• This column is a polymeric column suitable for chromatographic separation of inorganic anions and other macromolecules.
• the above polymeric material when packed in capillaries is also suitable for electrochromatographic separation of inorganic anions and other macromolecules.
• EXAMPLE 16 The separation of basic proteins in several polymer coated capillaries using the above bonding approach and a 50 mM sodium acetate buffer (pH 4.5) is shown in Figure 1.
• Figure 1 shows separations of basic proteins using various polymer coated capillaries.
• Capillary 50 cm total length; 45 cm to detector; 50 ⁇ m i.d.
• Buffer 50 mM sodium acetate at pH 4.5.
• Conditions 20 kV (400 V/cm); Gravity Injection: 50 mm x 10 s. Detection: UV, 210 nm. Sample concentration: 100 ⁇ g/ml.
• Peak identification (1) Lysozyme (Chicken Egg White), (2) Cytochrome c (Bovine Heart), (3) Ribonuclease A (Bovine Pancreas), (4) Myoglobin (Horse Skeletal Muscle), (5) a-Chymotrypsinogen A (Bovine Pancreas).
• the basic proteins show approximately the same migration times in all the capillaries.
• the capillary-to-capillary migration time variation was 3.12% (RSD), indicating a small EO flow variation between the capillaries.
• the efficiency generated in capillaries treated with (a) 4% PVP on MET silane, (b) 4% PVP on octyl silane, and (c) 2% polyacrylamide on MET silane were similar (app. 500,000 plates/50 cm). We observed no band broadening effects or efficiency loss due to hydrogen bonding interactions with the polymer for the above polymer coatings, contrary to the observations of Zhao et al. 16 and Strege and Lagu 9 .
• the coating was further tested for interaction with basic proteins under a variety of concentration conditions.
• the response versus concentration plots showed good linearity, and correlation coefficients (r 2 ) higher than 0.995 were obtained for all the tested proteins.
• the capillary generated more than 250,000 plates at a concentration of 300 ⁇ g/ml and more than 100,000 plates at a concentration of 1 mg/ml.
• the RSD in migration times in the tested range of 5 ⁇ g/ml to 1000 ⁇ g/ml was 1.6%, consistent with the long term performance of this capillary.
• the concentration detection limit for basic proteins under our experimental conditions was 5 ⁇ g/ml. Based on the linearity of response versus concentration curves, high efficiency under high concentration conditions, low detection limit, and minimal migration time variation under high analyte concentrations, we conclude that the analytes interacted minimally with the coating surface.
• the MET-PVP capillary remained stable under a variety of buffer and pH conditions.
• the EO mobility in this coated capillary was less than 2 x 10 "5 cmVV.s at pH 10 using a 10 mM borate buffer and tested for more than 48 hours.
• a fused silica capillary tested under the same conditions gave an EO mobility of 62.5 x 10" 5 cm 2 /V.s.
• the EO flow was substantially reduced by the polymer coating.
• the EO mobility in the polymer coated capillary increased from 1.5 x 10 '5 cm 2 /V.s to 5 x 10 "5 cm 2 /V.s after 40 h using a 50 mM sodium carbonate buffer at pH 11.
• EXAMPLE 19 The effect of polymer size and concentration on the coating performance was studied by coating several capillaries under the same conditions and testing them for basic protein separations using a 50 mM sodium acetate buffer at pH 4.5. (See Table 1 and Figure 3).
• Figure 3 shows the effect of polymer molecular weight and concentration on efficiency of basic proteins. All other conditions are the same as in Figure 1.
• the average efficiency was almost the same based on an RSD of less than 5%.
• the RSD in migration times for the various proteins was less than 2%, indicating that polymer size and concentration had a minimal influence on the coating performance.
• These results also indicated that the EO flow and shielding of surface silanols were nearly identical in these capillaries.
• Testing under alkaline conditions using a phosphate buffer at pH 8 gave an average EO flow of ⁇ 1.7 x 10 "5 cm 2 /N.s for all the capillaries (tested for more than 24 hours).
• the coating process was insensitive to the molecular weight change and concentration of the polymer. No optimization of the polymer size or concentration was required to achieve optimal performance, unlike the approach of Zhao et al. 16 Additionally, the coating thickness was optimal based on the high efficiencies observed using these coatings.
• EXAMPLE 20 Replacing the persulfate initiator system with an azo-based initiator system resulted in minimal change in performance for the MET-PVP capillary.
• the average efficiency for basic proteins in a MET-PVP coated capillary using an azo initiator was ⁇ 500,000 plates/capillary.
• EXAMPLE 21 The reproducibility of the coating process was studied by coating five capillaries in parallel with MET-PVP coating. The capillaries gave an RSD of less than 2.5%) in migration times for the basic proteins and confirmed the reproducibility of the coating protocol.
• EXAMPLE 23 The capillary was also useful in separating a standard mixture of seven inorganic anions (Figure 5).
• Figure 5 shows separation of test anions using a cationic polymer coated capillary.
• Capillary 50 cm total length; 45 cm to detector, 50 ⁇ m i.d.
• Buffer 1.6 mM Triethanolamine, 2.25 mM pyromellitic acid adjusted to pH 7.7 with IN NaOH.
• Conditions -20 kV (400 V/cm); Gravity Injection: 100 mm x 30 s.
• Detection Indirect UV, 250 nm. Sample concentration: 1 ⁇ g/ml. Peak identification: (1) Bromide, (2) Chloride, (3) Sulfate, (4) Nitrite, (5) Nitrate, (6) Fluoride, (7) Phosphate.
• the seven ions were baseline resolved using a pyromellitic acid containing buffer with efficiencies ranging from 30,000 plates/50 cm for fluoride to 140,000 plates/50 cm for nitrate. Analysis of the same ions using fused silica capillaries and indirect UV detection required special additives coupled with special pretreatment steps to achieve flow reversal in the anodic direction.
• EXAMPLE 24 Coupling mechanism. The following solution phase and CE experiments were performed to understand the mechanism of coupling the polymer to the silane.
• Literature on grafting vinyl 28 silanes and vinyl monomers 29 into polymer chains supports the covalent linkage of the polymer to the silane through double bonds on the silane. Similarly, linkage of the polymer to the silane through free radical sites created by hydrogen abstraction on other sites such as a ⁇ -carbon atom adjacent to the double bond is also possible. 30,31 Solution phase experiments were conducted to gain better understanding of the coupling mechanism.
• Treatment with fluoride ion is expected to inhibit silane condensation.
• extreme alkaline environment above pH 10
• 33 Treatment of the gel-like material mixture of PVP, silane, initiator treated at 80 °C) with sodium fluoride and heating the mixture at 50 °C for 18 h showed no change in the solution.
• the retention of gel-like behavior by the PVP-silane mixture suggests a covalent cross-linking reaction between the polymer and the silane.
• treating with IN NaOH also showed no change in the PVP-silane mixture, further reaffirming the above result.
• EXAMPLE 27 We performed solution phase experiments, simulating coupling of PVP to an octylsilane by thermal treatment of PVP in the presence of an in-house synthesized trimethyldecylsilane reagent and initiators in dichloromethane solvent. A highly cross-linked gel-like material was formed at the bottom of the flask after the 18 hour thermal treatment step. PVP polymer with added initiators and PVP in the presence of trimethyldecylsilane with no added initiators did not form a gel-like material under the same conditions. Trimethyldecylsilane has no reactive functional groups for chemical coupling reactions. The above experiment suggests the formation of a covalent cross-link between PVP and trimethyldecylsilane through a hydrogen abstraction mechanism.
• CE methods for analyzing milk proteins involve working at low buffer pH conditions with added polymer additives. 34 Due to the high pH stability of this coating, we attempted the above separations without adding any polymer additives at pH 8.4. Vitamin D milk was centrifuged at 8000 RPM for 4 minutes and incubated in a reduction buffer following a sample preparation procedure by Jong et al. 34 Excellent separation of the whey proteins from casein was achieved, as shown in Figure 6.
• Figure 6 shows separation of proteins from 2% Vitamin D Milk using a MET-PVP coated capillary. Capillary: 50 cm total length; 45 cm to detector; 50 ⁇ m i.d. Buffer: 100 mM sodium phosphate, pH 8.4 with 6M urea. Conditions: -30 kV (600 V/cm); Gravity Injection: 150 mm x 30 s. Detection:
• EXAMPLE 29 Analysis of Hemoglobin variants Baseline resolution of the four common variants of hemoglobin was achieved using a PVP-MET coated capillary with >650,000 plates/65-cm.
• the two commonly occurring normal hemoglobins are adult hemoglobin (HbA) and fetal hemoglobin (HbF).
• Sickle cell hemoglobin (HbS) is one of the abnormal hemoglobins, in which a single replacement of glutamic acid with valine occurs in position 6 of the beta chain, thus altering the solubility of this protein.
• HbC the individual has lysine instead of glutamic acid in position 6 on their beta chain. More than 50 runs of these samples were run without any loss in separation efficiency or performance. The unidentified leading component was present in all the human Hb samples. These separations were far superior to those shown in the literature. 35

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