Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/44—Preparation of metal salts or ammonium salts

Definitions

• the present invention concerns novel compositions and methods useful in high performance anion-exchange chromatography.
• the present invention relates to a novel composition which is useful for performing improved liquid chromatography. More particularly, the present invention relates to an improved composition and method for performing anion-exchange chromatography wherein the stationary phase employed exhibits enhanced hydrolytic stability in a variety of eluent solutions, particularly alkaline solutions such as carbonate and/or bicarbonate solutions.
• the presently described compositions therefore, allow one to perform anion-exchange chromatography over prolonged periods of time without significant loss of chromatography column performance.
• Anion-exchange chromatography is a well known technique for the analysis and separation of anions from solutions wherein the technique typically includes a chromatographic separation step using an eluent solution containing an electrolyte.
• ions of an introduced sample are eluted through a chromatography column which comprises an insoluble stationary phase to which functional anion-exchange groups are attached.
• Anions traversing through the column and contacting the stationary phase are then capable of exchanging at these positively-charged anion-exchange sites.
• quaternary ammonium groups are employed as the principle functional group of anion-exchange chromatography.
• anion-exchange stationary phases are commonly prepared from the commercially available compound glycidyl methacrylate which has been functionalized to possess a terminal quaternary ammonium salt. Once functionalized, the glycidyl methacrylate-derived compound possesses a terminal quaternary ammonium anion-exchange site whose nitrogen atom is separated from an ester group which is internal to the backbone of the compound by a total of three carbon atoms. While anion-exchange columns employing such stationary phases have found use for anion-exchange chromatography, such columns are often less than economically practical due to their inherent hydrolytic instability.
• the present invention is based, at least in part, on the novel finding that increasing the number of atoms in the chain between (1) a reactive chemical group, such as an ester, ketone or amide group, which is internal to the chain that links the anion-exchange site to the stationary phase and (2) the functional anion-exchange site itself results in enhanced hydrolytic stability and improved anion-exchange capacity.
• the present invention therefore, serves to address the common problem of limited stability of chromatographic stationary phases.
• an anion-exchange chromatographic composition which comprises:
• anion-exchange compounds attached to said synthetic resin support particles, wherein said anion-exchange compounds comprise a chain comprising (i) an ester, ketone or amide reactive group internal to said chain and (ii) an anion-exchange site terminal to said chain, wherein said anion exchange site consists of a quaternary ammonium salt which is capable of interacting with anions present in an eluent in contact therewith and wherein said quaternary ammonium salt is separated from said internal reactive group by a linker of at least 4 atoms in length.
• the internal reactive group of the anion-exchange compound is an ester group and/or the linker separating the internal reactive group from the nitrogen atom of the terminal quaternary ammonium anion-exchange site is from 4 to about 13 atoms in length, more preferably from 4 to about 6 atoms in length.
• the atoms from which the linker is composed may be carbon, oxygen or sulfur atoms which are either unsubstituted or substituted, preferably with alkyl, alkoxyl, hydroxyalkyl or hydroxy groups.
• the nitrogen atom of the terminal quaternary ammonium salt may also optionally be substituted by one or more substituents, preferably by alkyl or hydroxyalkyl groups.
• the above described anion-exchange compounds are attached to the synthetic resin support particles either directly through a covalent bond or by incorporation into a latex polymer which is then deposited onto the surface of the synthetic resin support particles.
• Another aspect of the present invention provides a latex polymer which has incorporated therein the above described anion-exchange compound and which is useful for depositing onto the surface of synthetic resin support particles to produce a hydrolytically stable anion-exchange chromatographic composition.
• Yet another aspect of the present invention provides a chromatography column which comprises the above described anion- exchange chromatographic composition for use in anion-exchange chromatography.
• a further aspect of the present invention provides a method for separating anions from a mixture of anions present in an eluent, wherein the method comprises contacting a chromatography column comprising the above described anion-exchange chromatographic composition with the eluent, thereby allowing anion-exchange to occur.
• the anion-exchange chromatographic composition of the present invention comprises synthetic resin support particles and anion-exchange compounds attached to those particles which comprise a chain comprising (i) a reactive group internal to said chain and (2) a terminal quaternary ammonium salt which functions as an anion-exchange site, wherein the internal reactive group and the nitrogen atom of the quaternary ammonium salt are separated by a linker of at least 4 or more atoms in length.
• the synthetic resin support particles of the presently described composition may be organic or inorganic in nature and may be formed from any resin material which will support the attachment of the anion- exchange compounds described below.
• synthetic polymer ion-exchange resins such as poly (phenol-formaldehyde), polyacrylic, or polymethacrylic acid or nitrile, amine-epichlorohydrin copolymers, graft polymers of styrene on polyethylene or polypropylene, poly(2- chloromethyl-1 ,3-butadiene), poly(vinylaromatic) resins such as those derived from styrene, alpha-methylstyrene, chlorostyrene, chloromethylstyrene, vinyltoluene, vinylnaphthalene or vinylpyridine, corresponding esters of methacrylic acid, styrene, vinyltoluene, vinylnaphthalene, and similar unsaturated monomers, monovinylidene monomers including the monovinylidine ring-containing nitrogen heterocyclic compounds and copolymers of the above monomers are suitable.
• synthetic polymer ion-exchange resins such as poly (phenol
• the synthetic resin support particles of the present invention can be formed, for example, by well known suspension polymerization techniques which involve suspending droplets of monomer in an aqueous medium in which it is insoluble. Under suitable conditions, the polymer will polymerize. This can be accomplished by mixing the monomer with additives in a suspension medium. When this medium is agitated, the monomer disperses into droplets and agitation continues until polymerization is complete.
• the synthetic resins used are of the macroporous type which are well known in the art, particularly including styrene-divinylbenzene copoiymer.
• the copolymer can be prepared, for example, according to the method of Ikada et al., Journal of Polymer Science 12:1829-1839 (1974) or as described in U.S. Patent No. 4,382,124 to Meitzner et al.
• Other techniques for the synthesis of synthetic resin support particles are well known in the art and can be found in U.S. Patent Nos. 3,91 5,642, 3,918,906, 3,920,398, 3925,01 9 and the monograph "Dowex: Ion Exchange” 3rd. edition, (1964) published by the Dow Chemical Company, Midland, Michigan.
• the synthetic resin support particles comprise beads of cross-linked polymer or copolymer, such as styrene-divinyibenzene copolymer which copolymerize in the presence of catalyst such as benzoyi peroxide, containing between about 0% to about 100% divinylbenzene monomer by weight. More preferably, the styrene-divinyibenzene copolymer contains between about 25% to about 80% divinylbenzene monomer by weight.
• catalyst such as benzoyi peroxide
• anion-exchange compounds Attached to the synthetic resin support particles of the anion- exchange chromatographic compositions of the present invention are "anion-exchange compounds" which comprise a reactive vinyl group, a chain comprising an internal reactive group, a terminal quaternary ammonium salt anion-exchange site and a linker separating the internal reactive group and the anion-exchange site.
• the anion-exchange compounds as described herein are derived from precursor molecules having a reactive vinyl group and the general formula (I):
• R is hydrogen or methyl
• X internal reactive group
• an internal reactive group (internal) because it is internal to the chain) which is an ester group is created.
• an internal reactive group which is an amide group is formed.
• the nitrogen of the internal amide group may be hydrogen- or alkyl from 1 to about 12 carbon atoms- substituted, preferably hydrogen-, methyl-, ethyl-, propyl-, isopropyl-, butyl- or isobutyl-substituted, more preferably hydrogen-substituted.
• the internal reactive group is an ester group that is incorporated into a latex polymer which is deposited onto the surface of the synthetic resin support particles.
• "F" of formula (I) may be either an epoxide group or a halogen atom. In the case of the latter, the halogen atom is preferably chlorine or bromine.
• the terminal epoxide group or halogen atom "F" provides a site at which an anion-exchange site may be formed.
• "F” is either an epoxide group or halogen atom
• a tertiary amine using well known techniques to produce a terminal quaternary ammonium salt which is capable of interacting with anions present in an eluent in contact therewith.
• the resulting compound (referred to herein as an anion-exchange monomer) has the following formula (II):
• R 3 , R 4 and R 5 are each independently hydrogen, straight-chain or branched alkyl from 1 to about 12 carbon atoms or straight-chain or branched hydroxyalkyi from 1 to about 1 2 carbon atoms.
• R 3 , R 4 and R 5 are each independently hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl or hydroxyalkyi, more preferably, methyl or hydrogen.
• R 3 and R 4 are methyl and R 5 is ethyl.
• R 3 and R 4 are methyl and R 5 is ethyl.
• the reaction creating the terminal quaternary ammonium anion- exchange site may occur prior to grafting the anion-exchange monomer to the surface of the synthetic resin support particle or prior to incorporation of the monomer into a latex polymer or after the precursor molecule is incorporated into a latex polymer or after the precursor molecule has been grafted to the surface of the synthetic resin support particle (see below).
• Group “L” of the precursor molecule of formula (I) and the anion- exchange monomer of formula (II) represents the linker group which serves to separate group "X" of the internal reactive group from the nitrogen atom of the terminal quaternary ammonium anion-exchange site.
• internal reactive groups such as ester, ketone and amide groups, when placed in close proximity (i.e., within 3 or fewer atoms) to the terminal quaternary ammonium anion-exchange site, are susceptible to hydrolysis, especially the type of hydrolysis that occurs in aqueous alkaline medium.
• L comprises a straight chain (not including branching) of at least 4 atoms in length, usually from 4 to about 13 atoms in length, more usually from 4 to about 10 atoms in length, preferably from 4 to about 6 atoms in length, more preferably 6 atoms in length, thereby providing for enhanced hydrolytic stability.
• “L” may be straight chain or branched, preferably straight-chain, and may comprise saturated or unsaturated carbon atoms and/or heteroatoms such as oxygen or sulfur atoms. “L” is preferably composed of saturated or unsaturated carbon atoms, more preferably saturated carbon atoms. In the case where, “L” is branched, the internal reactive group and the nitrogen atom of the terminal quaternary ammonium salt will still be separated by a chain of at least 4 atoms, wherein the branched linker group will usually comprise no more than 1 3 total carbon atoms, preferably no more than 10 carbon atoms total, more preferably no more than 7 carbon atoms total. Branching may occur at any atom in the linker chain, preferably at the atom adjacent to the internal reactive group, thereby providing additional protection against hydrolysis of the internal reactive group due to "steric hindrance".
• the linker group "L” may comprise carbon atoms or heteroatoms such as oxygen or sulfur.
• the linker group will contain from 0 to about 3 heteroatoms, more usually from 0 to 2, preferably from 0 to 1 and more preferably 1 heteroatoms.
• Heteroatoms will be placed in the linker groups at positions where they will have no significant effect on the anion separation characteristics of the composition. The determination of where heteroatoms may effectively be positioned in the linker chain is well within the skill level in the art.
• One or more atoms of the linker chain separating the internal reactive group from the nitrogen atom of the terminal quaternary ammonium salt may also be independently alkyl-, alkoxyl-, hydroxyalkyl- or hydroxyl-substituted. Such substitutions may conveniently be made at any atom of the linker chain.
• Alkyl, alkoxyl and hydroxyalkyi substituents usually have less than about 10 carbon atoms, more usually less than about 6 carbon atoms, preferably less than about 4 carbon atoms and more preferably less than about 3 carbon atoms.
• Substituents are often about two atoms removed from the nitrogen atom of the terminal quaternary ammonium salt as a result of functionalization of a terminal epoxide group with a tertiary amine to form the terminal quaternary ammonium salt. Hydroxy-containing substituents located adjacent to or near the terminal quaternary ammonium salt are preferred to compensate for the increased hydrophobicity of anion- exchange compounds having longer linker chains.
• anion-exchange compounds of the present invention may be prepared by reaction of the appropriate precursor molecule with tertiary amine and include, without being limiting of the invention, quaternary ammonium salts of epoxy- or halo-alkyl acrylates or methacrylates where alkyl comprises straight or branched chain alkyl groups with from about 4 to about 13 carbon atoms and optionally containing from 0 to about 3 heteroatoms.
• Such compounds include, for example, 2-glycidyloxyethyl methacrylate, 3,4- epoxybutyl methacrylate, 4,5-epoxypent-2-yl methacrylate, 4,5- epoxypentyl methacrylate and 2-glycidyloxyethyl methacrylate and amido- and keto-derivatives of the above.
• the first step generally involves the formation of an appropriate alkenyl acrylate followed by epoxidation of that alkenyl acrylate.
• the anion-exchange compounds which find use herein may be covalently bonded or grafted to the surface of the synthetic resin support particle by employing the method described in U.S. Patent No. 5,503,933, issued to Afeyan et al. Specifically, in the method described by Afeyan et al., both the compound being attached to a solid support and the solid support itself possess available unsaturated groups, such as vinyl groups, wherein the compound becomes covalently bonded to the solid support by a free radical reaction between available unsaturated groups. Because both the anion-exchange compounds and synthetic resin support particles of the present invention will possess such available unsaturated groups, the described method may be employed to covalently attach the anion-exchange compounds to synthetic resin support particles.
• the anion-exchange compound may be incorporated into a latex polymer which is deposited onto the surface of the synthetic resin support particles as described in U.S. Patent No. 5,324,752.
• the preparation of latex polymer involves the polymerization of a precursor monomer of formula (I) above (having a vinyl group at one terminus and either an epoxide group or halogen atom at the other terminus) with a divinyl cross-linking monomer which has an available vinyl group at each terminus and optionally another monovinyl monomer.
• the amount of the optional monovinyl monomer added to the reaction provides a means for diluting or controlling the relative number of quaternary ammonium anion-exchange sites that exist in the final polymer product.
• the above components are polymerized in the aqueous phase to form a suspension of colloidal particles which are commonly called latex which, in turn, are irreversibly attached to the solid phase via a "dispersant" material that possesses functional sites that irreversibly attach to both the latex polymer and the solid phase, thereby forming a permanent attachment therebetween.
• the polymerization reaction may be performed by conventional emulsion polymerization techniques, such as by heating and stirring a suspension of monomers in a suitable solvent in the presence of a suitable emulsifying agent.
• the polymerization may be carried out by a suspension, bulk or solution process followed by grinding the resin to a desired size by mechanical means such as ball mills, rod mills or the like.
• the cross-linking and optionally-added monovinyl diluent monomers may be formed from many different well-known synthetic resins.
• cross-linking monomers are molecules possessing vinyl groups at each terminus wherein the group separating the terminal vinyl groups may be, for example, aromatic or aliphatic and may possess one or more heteroatoms such as oxygen or sulfur.
• Optionally-added monomers possess one terminal vinyl group and preferably are acrylate- or methacry late-based.
• divinyl cross-linkers which find use in the present invention include, for example, diethyleneglycol dimethacrylate and ethylene methacrylate or respective acrylates thereof.
• Specific optionally-added monovinyl monomers include, for example, methyl methacrylate and 2-ethoxyethyl methacrylate or respective acrylates thereof.
• the relative reactivities of the selected monomer components are similar, thus assuring an approximately even distribution of each of the monomer units in the final latex polymer product.
• the epoxide or halogen group that has been incorporated into the polymer may be converted to a quaternary ammonium salt by reaction with a tertiary amine as described above.
• the polymer may first be attached to the synthetic resin support followed by conversion of the epoxide or halogen groups to quaternary ammonium salts.
• the latex polymer prepared as described above may be "deposited” onto the surface of a synthetic resin support particle (and thereby irreversibly attached thereto) via a bridge of "dispersant” material which irreversibly binds to both the latex polymer and the solid support particles, thereby forming a bridge between (see U.S. Patent No. 5,324,752).
• the dispersant may be any material which can inhibit or prevent agglomeration during suspension in the aqueous medium used for polymerization.
• the dispersant may be selected from any one of the methacrylic aid copolymers, polymaleates, sulfonated polymers, polyvinylpyrrolidone esters, plant-based gums, lignins and cellulose derivatives.
• the dispersant material can be formed of polyvinylalcohol, sulfonated lignin, polyvinylpyrrolidine, gum arabic, gelatin, maleic acid- vinylacetate copolymer or styrene-maleic anhydride copolymer.
• the dispersant comprises between about 0.1 % to about 25% dispersant by weight water.
• the irreversible attachment of a dispersant to the synthetic resin support particles can occur by covalent bonding via various mechanisms, one mechanism is by covalent bonding via a free radical polymerization reaction. Free radicals are typically generated in the resin support particle polymer being formed and sustain polymerization of the polymer as well as promote branching, the formation of new chains of bridging and cross- linking.
• An initiator can be utilized in the polymerization step of the resin support particle which starts and maintains the polymerization reaction. If the initiator concentration is high enough, more free radical sites are generated than can be consumed in the polymerization reaction, and other chemical species that are present, such as dispersant, can react with them. Thus, the dispersant can covalently link to the resin substrate particle polymer.
• polyvinylalcohol dispersant can become covalently linked to another polymer if the initiator concentration is high enough.
• Ikada et al. Journal of Polymer Science 12: 1829-1839 (1974).
• polyvinyl chloride can be chemically grafted to the dispersant. Kirk et al., Encyclopedia of Chemical Technology, 3rd ed. Vol. 23, pp. 888-890 (1983).
• a second method of irreversible attachment of dispersant to the resin support particles can be by permanent physical entanglement.
• relatively small polymers such as sulfonated lignin dispersant or polyvinylalcohol dispersant can become permanently entangled with the resin support particle polymer as the polymerization reaction occurs.
• the irreversible attachment of dispersant to the latex polymer produced as described above can occur by covalent bonding, such as described previously herein, or by electrostatic forces.
• the synthetic resin support particles can be made of styrene-divinyibenzene copolymer and the dispersant can be a mixture of sulfonated lignin and gum arabic dispersant.
• the sulfonated lignin can irreversibly attach to the synthetic resin support particles either by covalent bonding or by permanent entanglement, thereby providing a negatively-charged surface to which the latex polymer can be agglomerated electrostatically. Specific methods for carrying out the above may be found in U.S. Patent No. 5,324,752.
• the functionalized particles can be packed into chromatographic columns using well known methodology and be used for high performance anion-exchange chromatography.
• U.S. Patent No. 4,351 ,909 discloses methods for preparing chromotography columns where the agglomeration of latex polymers onto synthetic resin support particles is done before the column is pressure packed with those particles.
• chromatography columns may be pressure packed with synthetic resin support particles followed by the subsequent agglomeration of the latex polymer thereon. See U.S. Patent Nos. 4,438,047 and 4,351 ,909.
• anion-exchange chromatography compositions of the present invention are primarily useful for the separation of anions in aqueous eluent solutions employed in anion-exchange chromatography.
• these solutions are carbonate or bicarbonate solutions, preferably sodium or potassium carbonate solutions.
• the anion-exchange chromatographic compositions of the present invention may be employed in methods for separating anions from a mixture of anions. To do so, the anion-exchange compositions of the present invention are packed into chromatography columns for use in anion-exchange chromatography. The column is then contacted with a mixture of anions which are present in an eluent and anion-exchange is allowed to occur at the terminal ammonium salts of the anion-exchange compositions. Further details of the invention are illustrated in the following non- limiting examples.
• Step I 3-Butenyl methacrylate.
• methyl methacrylate 80 ml was added, followed by a methanolic solution of magnesium methoxide [prepared by dissolving magnesium metal (0.1 g) in anhydrous methanol (5 ml)].
• the stirred mixture was slowly heated and methanol was distilled off (bp 64-70°C) until the temperature at the distillation head rose to approximately 100°C and the methyl methacrylate started to distill.
• the mixture was then cooled to room temperature and the solids were filtered off. The filtrate was fractionated under vacuum. Pure 3-butenyl methacrylate was collected at bp 63-66°C/30 mmHg. Yield: 22.5 g.
• Step II 3,4-Epoxybutyl methacrylate.
• a solution of 3-butenyl methacrylate (5.1 g) was added slowly to the stirred solution of m-CPBA (10.2) in methylene dichloride (70 ml). The resulting solution was stirred at room temperature for 5 hours and then was washed repeatedly with a dilute aqueous solution of potassium carbonate. The solution obtained was then dried with anhydrous magnesium sulfate and evaporated. Pure 3,4-epoxybutyl methacrylate was isolated by column chromatography on silica gel. Yield 3.9 g.
• Step I 4-Pentenyl methacrylate.
• the preparation of 4-pentenyl methacrylate can be perfomed as described in U.S. Patent Nos. 2,863,851 and 3,001 ,975. However, for the purposes of the present synthesis, the synthesis was performed essentially as follows. To a solution of 4-penten-1 -ol (18.1 g) in N,N-dimethylaniline (40 ml) that was vigorously stirred and cooled in an external ice-bath, a solution of methacryloyl chloride ( 10 g) in methylene dichloride (40 ml) was added dropwise over 45 min.
• Step I 4-Penten-2-yl methacrylate.
• Sodium metal 0.2 g was dissolved in anhydrous methanol (3 g) and to this solution 4-penten-2-ol (1 8.5 g) was added followed by the addition of methyl methacrylate (50 g).
• the resulting mixture was stirred and heated until the methanol started to distill.
• the distilled methanol was collected at 64-70°C. After the removal of methanol was complete, the temperature was increased and at about 100°C methyl methacrylate began to distill. At this moment, the reaction mixture was cooled to room temperature and was divided between dilute sulfuric acid (1 N, 250 ml) and methylene dichloride ( 1 50 ml).
• Step II - 4,5-Epoxypent-2-yl methacrylate.
• a solution of m-CPBA (32 g) in chloroform (1 50 ml) was cooled in cold water and then 4-penten- 2-yl methacrylate (14 g) was added. The mixture was stirred at 23°C for 6 hours. The post-reaction mixture was then poured into dilute potassium carbonate (300 ml) and the organic layer was separated. The organic layer was washed with three more portions of carbonate, finally with water and then dried. Remaining solvents were then removed and the residue was subjected to chromatography on silica gel. As a result pure 4,5-epoxypent-2-yl methacrylate (9.5 g) was isolated.
• the solution was transferred into a separating funnel, was washed three times with water and then placed back in a reaction vessel which was being cooled in an ice bath. The mixture was stirred until the temperature dropped to -5°C at which time 50% aqueous sodium hydroxide (140 ml) was added. The temperature was maintained at -3°C. After the aqueous sodium hydroxide was added, the organic layer was separated and washed several times with water and then dried. Remaining solvents were removed and the residue was fractionated under vacuum, collecting the fraction with bp 75-82°C/0.1 mmHg.
• the resulting colorless liquid (33 g) contains ethylene glycol dimethacrylate (40%), glycidyloxyethyl methacrylate (50%) and diethylene glycol dimethacrylate (3%).
• a sample of this mixture ( 14 g) was subjected to purification using silica gel column. As a result, pure glycidyloxyethyl methacrylate was obtained. Yield 6.8 g.
• EXAMPLE 5 Preparation of a latex polymer comprising 2-qlvcidyloxyethyl methacrylate.
• potassium persulfate 0.4 g was dissolved in de-ionized water.
• sodium phosphate 0.1 g was added followed by the addition of monobasic potassium phosphate (0.05 g), Igepal CA-897 ( 1 .05 g), 2-glycidyloxyethyl methacrylate (1 .82 g), diethylene glycol dimethacrylate (0.1 8 g) and ethoxyethyl methacrylate (0.5 g).
• the contents of the bottle were stirred and then purged with nitrogen for 1 5 min.
• the latex polymer prepared in Example 5 above was functionalized as follows. Into a 100 ml stoppered bottle, the latex prepared in Example 5 above (5.0 g) was added followed by the addition of Igepal CA-897 (0.5 g), appropriate tertiary amine (7.0 g of 1 M aqueous solution) and nitric acid (1 .5 g of 1 M aqueous solution). The reaction mixture was left to stir at 32°C for 90 minutes. At the end of the reaction, the resulting latex size increased to approximately 100 nm with a polydispersity of approximately 0.09. The latex was stabilized by the addition of 7 g of 1 M acetic acid.
• Step I 2-(2-Dimethylaminoethoxy)ethyl methacrylate.
• a magnesium methoxide solution was prepared by dissolving magnesium metal (4 g) in anhydrous methanol (100 ml) in the presence of a small amount of iodine (approximately 0.1 g). A portion of the resulting solution ( 1 8 ml) was placed in a 250 ml reaction vessel and then 2-(2- dimethylaminoethoxy)ethanol (23.6 g) was added, followed by the addition of phenothiazine (0.1 g) and methyl methacrylate (1 17 g). The mixture was stirred and heated until the methanol started to distill.
• Step II 2-(2-Methacryloyloxyethoxy)ethyl-dimethylethylammonium bromide.
• 2-(2-dimethylaminoethoxy)ethyl methacrylate (8 g) was dissolved in acetone (20 g) and small amounts of hydroquinone (approx. 0.1 g) was added followed by the addition of bromoethane (8 g). The mixture was stirred at room temperature for 24 hours and the solvent was removed under reduced pressure at 25°C. Product was obtained as an amorphous solid. Yield 12.2 g.
• EXAMPLE 8 Hydrolytic stability of chromatographic stationary phases derived from glycidyl methacrylate versus 2-glvcidylo ⁇ yethyl methacrylate.
• Pressure packed anion-exchange chromatography columns were prepared from synthetic resin support particles by the agglomeration thereon of a functional latex polymer wherein the anion-exchange compound incorporated therein was either based upon the commercially available and commonly employed glycidyl methacrylate or upon 2- glycidyloxyethyl methacrylate as described in Examples 4-6. These chromatography columns were then tested in experiments designed to determine the hydrolytic stability of the stationary phases of each column under particular conditions. Specifically, both columns were tested at 60°C using a series of eluents, differring in composition and pH.
• “Exp. Time” refers to the time (hours:minutes) that the experiment was carried out
• “Ret. Time” refers to the observed retention time in minutes
• Adj. RT refers to the adjusted retention time which is the observed retention time minus the retention time of the "water peak” that corresponds to the 0.828 ml void volume of the column
• Dec. RT refers to the decrease in the retention time in minutes
• “Hydrolysis %” refers to the extent of hydrolysis of the anion-exchange sites from the column.

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