MODIFIED POLYMER SUPPORT MATERIAL, USABLE AS A STATIONARY PHASE IN AN ANALYTICAL OR PREPARATORY SEPARATION PROCESS

Description

[0001] The present invention relates to a method for modifying a polymer support material for use as a stationary phase in an analytical or preparative separation process, wherein the method comprises the steps of: providing a polymer support material at least partially composed of aromatic hydrocarbon compounds having at least two vinyl or allyl substituents; generating hydroxyl groups on / in the polymer support material by a process comprising an oxidative treatment of the polymer support material and a subsequent reductive or hydrolytic treatment of the reaction product; and reacting the product from the previous step with a polyfunctional compound. The invention further relates to a polymer support material for use as a stationary phase in an analytical or preparative separation process, in particular a chromatographic process, prepared according to a method according to the invention.

[0002] Ion exchangers are generally composed of particulate materials whose surfaces carry charges that enable them to retain ions. Anion exchangers are often cationic ammonium compounds, although phosphonium and arsonium ions are also known. The exchanger group is monocationic. In purely electrostatic interactions, the retention time is determined by Coulomb's law. According to this law, only the charge of the retained anion should affect its retention time.

[0003] In aqueous ion chromatography, however, further factors can be identified that affect retention behavior, such as the hydration of the anion and the hydration of the exchange group. The polarizability of the ions involved and weaker, secondary interactions between the analytes and the exchange substrate also play a role. Since the hydrophilicity of the base polymer supporting the exchange group also affects its hydration, the retention behavior of the ion exchanger can be altered for the same exchange group by modifying the support material. The direct substituents of the cationic group also influence retention behavior.

[0004] Approaches to adjusting the hydrophilicity of a particle for ion exchange chromatography already exist in the prior art. Other desirable parameters, such as balanced capacity, high theoretical plate number, or chemical inertness of the ion exchange material, are also discussed in some instances.

[0005] In US20050181224, cross-linked layers containing the ion exchange groups are deposited on a sulfonated hydrophilic support particle through the cyclic reaction of diepoxides and amines. With each cycle, the capacity of the ion exchanger increases. While hydrophilicity is generally ensured, the alternating epoxide / amine chemistry does not allow for the independent gain of additional hydrophilicity.

[0006] In EP 3248678, a porous divinylbenzene particle is coated with modified polysaccharides (agarose reacted with glycidyl phenyl ether), and the modified polysaccharide is subsequently crosslinked with a polyfunctional crosslinking agent (e.g., ethylene glycol diglycidyl ether) to form a macromolecule with hydroxyl groups on its surface. The substrate is then treated with diethylaminoethyl chloride hydrochloride to create the actual ion-exchange group. The application also aims to produce a hydrophilic ion-exchange particle with increased stability (rupture strength). However, due to the purely adsorption forces acting between the particle and the initially gel-like coating, the substrate proves to be less stable.

[0007] EP1217012 starts with a hydrophobic vinyl alcohol ester polymer. First, the esters are hydrolyzed, releasing alcohol groups. This makes the polymer hydrophilic. The OH groups are then reacted with a diepoxide and subsequently an amine to coat the substrate. The hydrophilicity could be further increased by subjecting the base polymer to more extensive hydrolysis in the first step. However, this would reduce the particle's mechanical stability. Undesirable swelling behavior may occur.

[0008] In a publication by Caglayan et al. (J Sep Sci 2006, 29, 940), an attempt is made to optimize some of the aforementioned parameters, such as theoretical plate number, pore size, and surface area, by using a particle substrate of poly(vinyl acetate-codivinylbenzene) of varying composition. According to the publication, an increased proportion of vinyl acetate—and thus an increased proportion of OH groups in the hydrolyzed particle—leads to a sharply rising reflux pressure when the column packed with the substrate is subjected to an increased flow rate. This undesirable reflux pressure is attributed to the lack of mechanical stability of the particles, which deform during the separation process.

[0009] US5503933 discloses hydrophilic coatings covalently bonded to hydrophobic surfaces and methods for their fabrication. To form the coated surfaces, a compound is provided comprising a hydrophobic domain including an unsaturated group and a hydrophilic domain. A hydrophobic surface with unsaturated groups is also provided. The compound molecules are adsorbed onto the hydrophobic surface, and the unsaturated groups in the hydrophobic regions of the compound molecules are then covalently bonded to the unsaturated groups on the hydrophobic surface via a free radical reaction. In one embodiment, the hydrophilic coatings can be covalently bonded to divinylbenzene-crosslinked polystyrene. However, the resulting particles are only suitable for the separation of macromolecules.For use in other chromatographic methods, especially ion chromatography, the particles have an unsatisfactory theoretical plate number due to their large diameter. Conversely, with a reduced particle size, the mechanical strength of the macroporous material would not be sufficient for the pressures generated in such chromatographic methods.

[0010] The object of the present invention is to overcome the aforementioned disadvantages of the prior art. Currently, there is no method by which a polymer substrate can be coated in such a way that the hydrophilicity of the polymer support material surface can be adjusted independently of the oxygen content in the polymer core substrate, resulting in a mechanically stable and robust particle. At the same time, an ion exchange substrate based on this should be largely chemically inert, and hydrophilicity and capacity, or selectivity and capacity, should be configurable independently of one another.

[0011] This problem is solved by a method having the features of claim 1. It is a method for modifying a polymer support material for use as a stationary phase in an analytical or preparative separation process. The invention further relates to a polymer support material for use as a stationary phase in an analytical or preparative separation process, in particular a chromatography process, produced according to a method according to the invention. The invention relates to a chromatography column filled with the polymer support material according to the invention, a method for separating analytes using the polymer support material according to the invention, and the use of the polymer support material according to the invention for the analytical and preparative separation of analytes.

[0012] The process comprises the following steps: providing a polymer support material at least partially composed of aromatic hydrocarbon compounds having at least two vinyl or allyl substituents, preferably at least partially composed of divinylbenzene monomers, wherein the provided polymer support material has an average pore radius of 1 to 50 nm, preferably 2 to 25 nm, particularly preferably 2 to 10 nm, measurable by nitrogen sorption in the BJH model, and a specific surface area of ​​80 to 1000 m² / g, preferably 100 to 800 m² / g, even more preferably 200 to 600 m² / g, measurable by nitrogen sorption in the BET model (step a); generating hydroxyl groups on / in the polymer support material by a process comprising the following steps: oxidative treatment of the polymer support material (step b.1); subsequent reductive or hydrolytic treatment of the reaction product from step b.1 (step b.2); optional: reaction of the product from step b.2. with a polyfunctional compound, in particular a compound having at least one first functional group that is reactive with hydroxy groups, preferably a halogen group, and at least one second functional group that is reactive with amines and / or hydroxy groups, preferably an epoxide group (step c).

[0013] It goes without saying that a functional group reactive with amines is also reactive, or may be reactive, with other organometallic compounds of the 5th main group, namely with arsines or phosphines.

[0014] As will be explained in more detail below, particularly with regard to the inventive method, the steps according to the invention affect the oxygen content at the polymer support material surface. The hydrophilicity of the polymer support material surface is therefore independent of the oxygen content in the polymer support core substrate.

[0015] The polymer support material provided in step a. is typically provided as particles, preferably as spherical particles, particularly preferably as spherical particles with an average particle size (median) of 1 to 50 µm, even more preferably with an average particle size of 2 to 25 µm, and particularly preferably with an average particle size of 3 to 9 µm. However, other polymer support materials are also conceivable, in particular polymer support materials in the form of membranes or monoliths.

[0016] The oxygen content at the surface of the polymer support material is increased by the initial oxidation and reduction or hydrolysis. Through this modification, oxygen atoms can also be generated on / in a core polymer support material that has no detectable oxygen content. The increased oxygen content influences the type and extent of secondary interactions, particularly the hydrophilicity of the resulting polymer support material. Furthermore, through a series of steps following the initial oxidation and reduction / hydrolysis, the capacity can be adjusted independently of the oxygen content at the surface.

[0017] The term "surface of the polymer support material" or "polymer support material surface" refers specifically to the solution-contactable outer surface of the polymer support material structure, as well as the layer immediately adjacent to this outer surface, ranging from 1 to 30 nm in thickness. This solution-contactable outer surface may be partially located on microstructures of, for example, porous structures. In particular, this refers to the solution-contactable outer surface of polymer support material particles of porous or non-porous structure.

[0018] The covalent bond between the polymer support material and the coating makes a first contribution to chemical and mechanical stability. This contrasts with the situation in latex-based ion exchangers, where purely electrostatic interactions hold the latex grains, and thus the exchange groups, to the substrate. High chemical inertness is also ensured due to the covalent bond. A second contribution to mechanical stability is made by the fact that the core polymer support material is at least partially composed of aromatic hydrocarbon compounds and contains at least two vinyl or allyl substituents, preferably at least partially composed of divinylbenzene monomers. The stability of this core polymer support material is not affected by steps b.1 and b.2. The core polymer support material is preferably monodisperse.

[0019] Step c, i.e., the reaction of the product from step b.2 with a polyfunctional compound, in particular a compound having at least one first functional group reactive with hydroxyl groups and at least one second functional group reactive with amines and / or hydroxyl groups, is optional. If this step is omitted, the particle is suitable, for example, for use in size exclusion chromatography.

[0020] The following describes in particular the production of ion exchange material for use in anion exchange chromatography or cation exchange chromatography based on the polymer support material modified according to the invention. However, the use of the particles is by no means limited to this. The particles can also be used in other analytical and preparative separation methods, such as other adsorption chromatography techniques, HILIC chromatography (hydrophilic interaction liquid chromatography), reversed-phase chromatography, solid-phase extraction, etc.

[0021] In a preferred embodiment, the method comprises steps a, b, and c as described above, as well as further steps following step c, namely, carrying out a number of coating cycles (step d). A single coating cycle, step d, comprises: introducing or generating hydroxy groups by reacting the second functional group, which is reactive with amines and / or hydroxy groups, preferably the epoxide group, introduced in step c, with a polyfunctional compound having hydroxy groups, in particular with a polyol or by hydrolysis or a combination thereof (step d.1); and reacting the product from step d.1.with a polyfunctional compound, in particular a compound comprising at least one first functional group reactive with hydroxyl groups, preferably a halogen group, and at least one second functional group reactive with amines and / or hydroxyl groups, preferably an epoxy group (step d.2). The number of coating cycles is between 0 and 20.

[0022] If the number of coating cycles is at least 2, the introduction or generation of hydroxy groups from the first repetition onwards naturally no longer concerns, or at least no longer exclusively concerns, functional groups introduced in step c, but primarily corresponding functional groups introduced in step d.2. This applies especially if the conditions are chosen such that the second functional groups from step c react essentially completely during the execution of the first coating cycle in step d.1.

[0023] By increasing the number of coating cycles, the oxygen content at the surface of the polymer support material can be further increased, thus enhancing the hydrophilicity of an ion exchange material based on this polymer support. Selecting a suitable degree of hydrophilicity allows for the enhancement of the ion exchanger's interactions with highly hydrated ions (such as fluoride) and the reduction of its interactions with weakly hydrated ions (such as bromate, nitrate, and chlorate). This can, for example, influence the retention order of bromate and chloride, ensuring that bromate is quantifiably present before chloride in the chromatogram. Furthermore, it can guarantee that fluoride exhibits separation from the injection peak, particularly when using a carbonate eluent.

[0024] Furthermore, the inventive method yields an ion exchange material with plate numbers of > 50,000 TP / m of theoretical plates per column meter for the seven standard anions (fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate) with high signal symmetries (asymmetry < 1.5). All of the above-mentioned ions appear baseline-separated from each other in the chromatogram with a short overall chromatographic runtime.

[0025] The advantages of the particles' high robustness become particularly evident when a column packed with a polymer support material obtained according to the above method is subjected to a pressure-flow test. In such a stress test, the pressure development in the column is determined as a function of a continuously increasing flow rate. In the column according to the invention, the pressure depends linearly on the flow rate. This contrasts with results obtained with conventional columns packed with hydrophilic pDVB substrate having a high vinyl acetate content. In conventional columns, the pressure increases more than linearly with the flow rate. For example, a hyperbolic slope of the function can result. This is shown, for instance, in the publication by Caglayan et al. cited at the beginning (J Sep Sci 2006, 29, 940).

[0026] The performance of the column according to the invention is also superior to that of conventional columns after a pressure test. Firstly, after the load test, the column exhibits only a slight increase in the pressure drop across the column compared to conventional columns. Secondly, the number of theoretical plates decreases significantly less during a load test on the column according to the invention than is the case with conventional columns (Caglayan et al., J Sep Sci 2006, 29, 940). Maintaining the pressure conditions and the number of plates, even at high flow rates, enables efficient high-performance separation processes.

[0027] The process can then additionally include step e, the introduction of ion exchange groups onto the reaction product from step c or d.2. Step e transforms the polymer support material into an ion exchange material that realizes the advantages associated with the polymer support material. Hydrophilicity and capacity, or selectivity and capacity, can be independently adjusted in this ion exchange material according to the invention. Furthermore, the ion exchange material according to the invention has a high number of theoretical plates.

[0028] Ion exchange groups are understood to be charged groups on the surface of the polymer support material, in particular charged amine, arsine or phosphine groups.

[0029] In the context of this invention, a polymer support material, which is at least partially composed of aromatic hydrocarbon compounds having at least two vinyl or allyl substituents, is understood to mean that the polymer support material can be produced by a polymerization reaction involving at least aromatic hydrocarbon compounds having at least two vinyl or allyl substituents. Preferably, the polymer support material is formed by polymerization reactions with divinylbenzene. However, reactions with trivinylbenzene and divinylnaphthalene, as well as compounds known to those skilled in the art as equivalent, are also conceivable.

[0030] The process can be characterized in that the polymer support material in step a, which is at least partially composed of aromatic hydrocarbon compounds having at least two vinyl or allyl substituents, is additionally partially composed of monomers selected from the group consisting of ethyl vinylbenzene, vinyl acetate, styrene, and a combination thereof. The proportion of aromatic hydrocarbon compounds having at least two vinyl or allyl substituents is preferably at least 50 wt.%. For example, the polymer support material in step a can consist of at least 50 wt.% divinylbenzene units. Such a polymer support material has advantageous properties with regard to its pore structure and, in particular, exhibits a high number of available double bonds for subsequent surface modification.

[0031] The process can be characterized in that the oxidative treatment in step b.1 is a treatment with a peracid, preferably selected from the group consisting of meta-chloroperbenzoic acid (m-CPBA), peroxyformic acid, peroxyacetic acid, peroxytrifluoroacetic acid, a treatment with KMnO₄, a treatment with oxygen plasma, or a combination thereof. By acting on the polymer with a peracid, existing double bonds are oxidized and made accessible to subsequent reduction or hydrolysis. It is understood that the effect can also be achieved in principle by other oxidative processes known to those skilled in the art, such as ozonolysis.

[0032] It is particularly preferred to use a peracid in step b.1. The advantage of peracids is that higher oxygen concentrations can be achieved than, for example, with plasma treatment. Oxygen plasma can achieve oxygen concentrations of 2.0%, while mCPBA, for example, can achieve oxygen concentrations of 3.2%, measurable by elemental analysis. If a peracid is used, it can be added to the polymer in suspension or in situ m-CPBA is formed from an acid and hydrogen peroxide. Preferably, the suspended core polymer support material, e.g., PS / DVB polymer support material, is mixed with m-CPBA, as it is easy to handle as a solid.

[0033] In a preferred embodiment, the reductive treatment of the reaction product from oxidation step b.1 in step b.2 is carried out with a reagent for the reduction of polar bonds, preferably with a metal hydride. This can be, for example, NaBH₄, BH₃, LAH, NaH, or CaH. The use of hydrides has the advantage that the dissolved reagent can penetrate the pores of the particle. This is not possible, for example, with palladium on activated carbon. Compared to hydrolysis with hydrochloric acid, which can convert epoxides to hydroxyls (see Example 3), reduction with metal hydrides can also convert carbonyls and carboxyls to hydroxyls. The reduction converts the oxidation products formed into alcohols. Lithium aluminum hydride in diethyl ether is preferably used for this purpose.In one embodiment, a 1-20% w / v polymer suspension in dry diethyl ether is prepared, to which 5-100% w / w of the polymer dry mass of lithium aluminum hydride is added. Particularly preferably, a 5-15% w / v polymer suspension in dry diethyl ether is prepared, to which 5-20% w / w of the polymer dry mass of lithium aluminum hydride is added. A temperature of 25-70°C can be selected, particularly preferably the boiling point of diethyl ether, as well as a reaction time of 1 min to 72 h, particularly preferably 3 h to 48 h.

[0034] The OH groups generated on the polymer support material surface by the process described above are now available in sufficient numbers for the modification in step c. Hydrolytic conditions can be chosen as an alternative to reductive conditions.

[0035] The reaction product from step b.2 is reacted with a polyfunctional compound, in particular with a compound having at least one first functional group that is reactive with hydroxy groups, preferably a halogen group, and at least one second functional group that is reactive with amines and / or hydroxy groups, preferably an epoxide group.

[0036] The first functional group, reactive with hydroxyl groups, can be a structure that can be nucleophilically attacked by OH or amine groups, such as a halogenated hydrocarbon, an epoxide, a tosylate, a methyl sulfide, or a mixture thereof. The second functional group, reactive with amines and / or hydroxyl groups, can be, for example, an epoxide. Preferably, the polyfunctional compound in step c is epichlorohydrin (ECH). For example, the substrate can be suspended in epichlorohydrin (preferably 5–30% w / v solid in ECH, particularly preferably 10–20% w / v solid in ECH). It can then be reacted with a base, such as aqueous alkali and alkaline earth metal hydroxides. Aqueous solutions of NaOH and KOH, particularly preferably 10–50% w / w NaOH in the ratio ECH:NaOH(aq) = 1:(0.1–10), have proven suitable for this purpose. The reaction is particularly preferably carried out using a quaternary ammonium salt as a phase transfer catalyst.Alternatively, the substrate suspended in ECH can be reacted with a quaternary ammonium hydroxide. Tetramethylammonium hydroxide has proven suitable for this purpose. Preferably, the suspension of polymer in ECH prepared according to the above is mixed with the same amount of dimethyl sulfoxide (DMSO) as ECH, and preferably between 1 and 10 mmol of tetramethylammonium hydroxide in concentrated aqueous solution is added per gram of polymer used, particularly preferably between 2 and 5 mmol of tetramethylammonium hydroxide (aq).

[0037] The polyfunctional compound used in step c, which has at least one first functional group reactive with hydroxy groups and at least one second functional group reactive with amines and / or hydroxy groups, can also be a spacer molecule.

[0038] In the context of this application, a spacer molecule (or simply spacer) is a molecule comprising the aforementioned at least two functional groups, wherein the molecule ensures a distance of at least 3 atoms, preferably 3 to 20 atoms, between the modified polymer support material surface and the ion exchange groups to be incorporated. In the finished ion exchange material, the spacer molecule binds to the modified polymer support material on one side and to the exchange group on the other. The functional groups of the spacer molecule can be nucleophilically attackable structures via OH or amine groups, such as halogenated hydrocarbons, epoxides, tosylates, methyl sulfides, or a mixture thereof. The spacer atoms can be carbon chains or heteroatoms, for example, ether groups or thioethers. The spacer molecule achieves this distance between the substrate and the ion exchange group.The function of the spacer is to prevent the ions from interacting with the substrate. This counteracts unwanted peak broadening in the chromatogram. Spacer carbon chains with ether groups are preferred due to their higher hydrophilicity. The spacer preferably contains glycidyl groups, which can react with amines, phosphines, arsines, and / or hydroxyl groups. The spacer molecule 1,4-butanediol diglycidyl ether is particularly preferred.

[0039] If, in step d.1, hydroxyl groups are introduced by reaction of the second functional group introduced in step c (or optionally in step d.2) by reaction with polyfunctional compounds containing hydroxyl groups, the use of a diol is preferred. Butanediol is particularly preferred. The diol can be used as both solvent and reactant, and the reaction can take place under base catalysis at elevated temperature. Particularly preferably, 0.1–1 mol / L KOH is used at 60–160°C for 1–48 h. Most preferably, the temperature is 100–130°C and the reaction time is 3–36 h. Upon addition of such a compound, previously substrate-bound epoxides are converted to OH-group-containing chains.

[0040] In one embodiment, the polyfunctional compound used in step d.2, which has at least one first functional group reactive with hydroxyl groups and at least one second functional group reactive with amines and / or hydroxyl groups, is an epihalohydrin, preferably an epichlorohydrin. The support polymer particle can first be suspended in epichlorohydrin (preferably: 5-30% w / v solid in ECH, particularly preferably 10-30% w / v solid in ECH). The suspension can then be reacted with a base, for example, aqueous solutions of alkali or alkaline earth metal hydroxides. Aqueous solutions of NaOH and KOH, particularly preferably 10-50% w / w NaOH in the ratio ECH:NaOH(aq) = 1:(0.1-10), have proven suitable for this purpose. The reaction is particularly preferably carried out using a quaternary ammonium salt as a phase-transfer catalyst.

[0041] Alternatively, a spacer molecule can be used in step d.2. It is particularly preferred if a spacer molecule is used at least in the last execution of the coating cycle in step d.2.

[0042] It is a preferred feature of the present invention that steps d.1 and d.2, which together are also referred to as a coating cycle, can be repeated. The number of coating cycles can be between 0 and 20, preferably between 0 and 10. However, it is preferred that the number of coating cycles be between 0 and 5, and even more preferably between 1 and 3.

[0043] With each cycle, the hydrophilicity of the polymer support material increases. By appropriately selecting the number of cycles, the hydrophilicity can be optimally tailored to the mixture to be separated. In particular, by choosing a suitable degree of hydrophilicity, hydrophilic interactions of the substrate with highly hydrated ions (such as fluoride) can be enhanced, while interactions with weakly hydrated ions (such as bromate, nitrate, and chlorate) can be reduced. This allows the retention order to be influenced. Furthermore, with each layer formation, the secondary interactions between polarizable ions such as chlorate or bromate and the substrate are reduced. The tailing of signal peaks, which is observed due to such secondary interactions, decreases significantly, so that even polarizable ions elute symmetrically. The overall capacity of the exchange material decreases.

[0044] In a preferred embodiment, a spacer molecule, in particular a diepoxide, preferably butanediol diglycidyl ether, is used as a polyfunctional compound in step d.2 of the final iteration of the coating cycle d. The advantages of a spacer molecule have already been described above in connection with step c. The reaction of a spacer molecule preferably takes place with the addition of a polar solvent to the reaction mixture, particularly preferably DMSO in a volume ratio of 1:(0.1-5), particularly preferably in a ratio of 1:(0.5-1.5) based on diglycidyl ether. The use of a quaternary ammonium salt as a phase-transfer catalyst is also preferred, particularly preferably tetrabutylammonium bromide in the concentration range of preferably 1-100 mmol / L, particularly preferably 10-50 mmol / L, based on the total volume of the reaction mixture.Alkali and alkaline earth metal hydroxides and carbonates can be used as the base, preferably aqueous solutions of NaOH and KOH, particularly preferably NaOH in the concentration range of 0.1–5 mol / L, and most preferably in the concentration range of 0.1–1 mol / L. The volume ratio based on the diglycidyl ether is 1:(0.1–5), preferably 1:(0.5–1.5). The preferred reaction temperature is 0–50°C, particularly preferably 20–30°C, with a preferred reaction time of 2–40 h, particularly preferably 15–25 h.

[0045] In a preferred embodiment, the ion-exchange group is introduced by reacting the compound from step c or d.2 with an organometallic compound of group 5, preferably an amine, and particularly preferably a tertiary amine. However, the ion-exchange group can comprise a phosphine or arsine instead of the amine. A compound containing an amine with 1 to 3 organic residues of 1 to 10 carbon atoms per residue, including cyclic compounds, has proven particularly suitable. The cyclic compounds can contain substituents. Examples of suitable compounds are nitrogen-containing heterocycles, for example, pyridines with or without hydrocarbon or hydroxy substituents, singly substituted alkylpyrrolidines, singly substituted alkylpiperidines, or doubly substituted alkylpiperazines. The hydrocarbon residues of the amine compounds can also be heteroatoms, e.g.,contain oxygen or sulfur atoms, or other substituents.

[0046] However, it would also be conceivable to introduce compounds suitable for cation exchange chromatography or HILIC methods. Suitable cationic functional groups include sulfonic acids, carboxylic acids, or combinations thereof. Preferably, the compounds to be introduced may also have multiple functional groups, for example, when amino acids are introduced.

[0047] To generate a cationic exchange center, for example, the polymer epoxidized in the previous step can be suspended in a mixture of water and a polar solvent, preferably DMSO, and a preferred amine can be added. The preferred reaction time is between 0.5 and 48 hours at a preferred temperature of 20–70°C.

[0048] It is preferred that step e, the introduction of ion exchange groups, is followed by a further step f comprising heating the polymer support material equipped with ion exchange groups in alkaline solution. This allows the selectivity and capacity of the ion exchange material to be adjusted from the preceding step. The treatment is hereinafter referred to as elimination and consists in particular of heating the particles equipped with exchange groups in aqueous alkaline solution, especially preferably heating in an aqueous solution of alkali or alkaline earth metal hydroxide or carbonate, for example, in sodium hydroxide solution. The preferred concentration of NaOH is in the range of 0.1 to 5 mol / L base, 0.2 to 2 mol / L base is particularly preferred. The reaction temperature can be 20–100°C, 90–100°C is particularly preferred, with a treatment time of 0.1–150 h, 2–6 h particularly preferred.

[0049] The elimination step alters the relative intensity of the substrate's interaction with individual ions. In particular, secondary interactions with polarizable analytes can be reduced. The tailing of signal peaks, observed due to such secondary interactions, decreases, allowing polarizable ions to elute symmetrically. Simultaneously, the electrostatic interaction capability of the column is reduced after elimination, and the overall capacity of the ion exchange material decreases.

[0050] Another aspect of the invention relates to a polymer support material for use as a stationary phase in an analytical or preparative separation process, in particular chromatography processes, obtainable by a process comprising the steps as described above, at least steps a, b and c.

[0051] A further aspect of the invention relates to a polymer support material for use as a stationary phase in an analytical or preparative separation process, in particular chromatography processes, obtainable by a process comprising the steps as described above, at least steps a and b, preferably at least steps a, b and c, wherein the polymer support material provided in step a is hydrophobic and microporous or mesoporous. Hydrophobic here means that the polymer support material is nonpolar, i.e., it has no monomer units with a dipole moment > 0.2 D. Microporous or mesoporous here means that the polymer support material has an average pore diameter of at most 50 nm.

[0052] Another aspect of the invention relates to a modified polymer support material for use as a stationary phase in ion exchange chromatography, if the process comprises at least steps a, b, c and e.

[0053] A modified polymer support material obtained in this way is characterized by the fact that When examining a cross-section of the polymer support material using X-ray photoelectron spectroscopy (XPS), differences of at least 20%, preferably at least 50%, and particularly preferably 100% are detectable between areas with maximum oxygen content and areas with minimum oxygen content, in each case starting from the value of the maximum oxygen content; the oxygen-containing groups are covalently bonded to the core polymer support material; the polymer support material is mechanically stable, such that the pressure drop across a column packed with the polymer support material increases only linearly as a function of an increased flow rate; the polymer support material carries no charge at neutral pH; the polymer support material has a nitrogen content of less than 2%.

[0054] The modified polymer support material exhibits a higher oxygen content, particularly on its surface, than in its core. Furthermore, the modified polymer support material obtained by the process is largely chemically inert. The polymer support material thus modified is adjustable in that it can have a more or less oxygen-containing surface. Due to its structure and surface properties, the material is particularly suitable for use as a stationary phase in analytical or preparative separation processes. In particular, the substrate is suitable for further processing into particulate ion exchange material produced according to the process described above, which is also part of the invention. However, the polymer support material can also be further processed for use in other adsorption chromatography methods, HILIC processes, reversed-phase chromatography, solid-phase extraction, etc.Thanks to its microporosity or mesoporosity, the modified polymer support material is suitable for the production of a column with a high number of theoretical plates with correspondingly good separation performance, since the micro- and mesoporous particles are mechanically stable even at small diameters and the diffusion paths can therefore be set shorter.

[0055] Another aspect of the invention relates to a polymer support material modified according to the invention for use as a stationary phase in ion exchange chromatography, obtainable by a process comprising the steps as described above, wherein ion exchange groups are additionally introduced into the polymer support material according to step e.

[0056] An ion exchange material obtained in this way can be characterized by the fact that When examining a cross-section of the polymer support material using X-ray photoelectron spectroscopy (XPS), differences of at least 20%, preferably at least 50%, and particularly preferably 100% are detectable between areas with maximum oxygen content and areas with minimum oxygen content, in each case starting from the value of the maximum oxygen content; the oxygen-containing groups are covalently bonded to the core polymer support material; the ion exchange material is mechanically stable, such that the pressure drop in a column packed with the polymer support material increases only linearly as a function of an increased flow rate; the ion exchange material, with the exception of the introduced ion exchange groups, is not based on modifications by means of epoxy-amine reactions, optionally detectable by Hofmann elimination; optionally, the ion exchange material has a plate number > 50,000 TP / m;Optionally, selectivity and capacity can be additionally adjusted with elimination step f.

[0057] The ion exchange material exhibits a higher oxygen content, particularly at its surface, than in its core. For example, the surface of a modified polymer support material produced according to the inventive method up to and including step c exhibits an oxygen content that is 50% higher, preferably 60% higher, than the inner particle regions, based on the value of the maximum oxygen content, as can be demonstrated by XPS measurements.

[0058] A key advantage of the ion exchange material according to the invention is that hydrophilicity and capacity, or selectivity and capacity, can be configured in individual steps, i.e., independently of one another. The ion exchange material produced according to the inventive method exhibits only weak secondary interactions with polarizable ions and increases the retention time of highly hydrated ions. A column packed with the hydrophilized ion exchange substrate exhibits the desired selectivity. The material does not swell and shows advantageous properties in stress tests. A particularly high-performance column can be packed with this ion exchange material.

[0059] The polymer support material described above is suitable for use as a stationary phase in ion chromatography, particularly for the separation of the standard ions fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate. A high ion exchange capacity of the column is essential, especially for the separation of small, mono- or doubly charged ions. Convective or perfusive mass transport of the analyte solution, as achieved by macroporous structures, is not desirable. Furthermore, macroporous structures are often associated with inferior mechanical strength.

[0060] The invention further relates to a modified polymer support material as described above, wherein the polymer support material provided in step a is essentially entirely composed of monomer units selected from the group of: monomer units derived from aromatic hydrocarbon compounds having at least two vinyl or allyl substituents, preferably derived from divinylbenzene; monomer units derived from ethylvinylbenzene; monomer units derived from styrene; or a combination thereof.

[0061] The term "essentially completely constructed" here means that the total proportion of the listed monomer units in the polymer support material provided in step a is at least 95 wt.%, preferably at least 98 wt.%, and particularly preferably at least 99 wt.%. In other words, the monomers can be essentially completely derived from compounds that do not contain oxygen atoms, resulting in a hydrophobic particle core.

[0062] Another aspect of the invention relates to a modified polymer support material as described above, wherein the polymer support material provided in step a has an average pore radius of 1 to 50 nm, preferably 2 to 25 nm, and particularly preferably 2 to 10 nm, measurable by nitrogen sorption in the BJH model, and a specific surface area of ​​80 to 1000 m² / g, preferably 100 to 800 m² / g, and even more preferably 200 to 600 m² / g, measurable by nitrogen sorption in the BET model. The measurement is carried out as described below in Example 5. The high specific surface area increases the capacity and resolving power of the column, particularly when separating small ions, for example, standard ions.

[0063] Another aspect of the invention relates to a modified polymer support material as described above, wherein the polymer support material provided in step a exhibits pressure stability up to 220 bar, preferably up to 250 bar. Pressure stability here means that the pressure increase is linear with respect to the flow rate. The measurement is carried out as described below in Example 6. The high pressure stability results from the small particle diameter and the micro / mesoporosity of the particle structure.

[0064] Preferably, the modified polymer support material is in the form of particles, preferably spherical particles, and particularly preferably spherical particles with an average particle size (median) of 1 to 50 µm. Particularly preferably, the particles are in the size range of 2 to 25 µm, and most preferably in the size range of 3 to 9 µm. Particle size is defined here as the mean value between the longest and shortest straight lines through the center of the particle, measurable by scanning electron microscopy (SEM) and automated image analysis.

[0065] The particle size can be adjusted by appropriate stirring speed, choice of solvent, polymer concentration in the solvent, etc. These methods are known to those skilled in the art. A support polymer of this shape and size has a volume-to-surface-area ratio that has proven particularly advantageous for the exchange capacity. It exhibits high diffusivity into the pores and is easily packable.

[0066] One aspect of the invention relates to a modified polymer support material as described above, wherein the modified polymer support material is stable in the pH range of 0 to 14. pH stability here means that the retention time of sulfate in a column packed with the modified polymer support material, after rinsing with 1 M NaOH solution and / or rinsing with 1 M HCl solution, does not deviate by more than 8%, preferably not more than 5%, and particularly preferably not more than 3% from the retention time of sulfate in a column packed with the modified polymer support material that has not previously been exposed to pH values ​​of 0 and / or 14. The measurement method for pH stability is described in Exemplary 8 below.

[0067] Another aspect of the invention relates to an ion exchange chromatography column filled with modified polymer support material, preferably particulate modified polymer support material, which can be produced using the method according to the invention.

[0068] Furthermore, the invention relates to a method for the chromatographic separation of analytes, characterized in that a solution containing the analytes is contacted with a modified polymer support material according to the invention, in particular by passing through an ion exchange chromatography column according to the invention.

[0069] The invention further relates to the use of polymer support material according to the invention, obtainable with the inventive method for the analytical or preparative separation of analytes, in particular use in anion exchange chromatography, cation exchange chromatography and / or in HILIC chromatography (hydrophilic interaction liquid chromatography).

[0070] To further illustrate the invention, the following exemplary embodiments are described. These exemplary embodiments have no limiting effect on the scope of disclosure or the claim of the invention.

[0071] The following figures are shown: Fig. 1: Schematic representation of exemplary modification sequences on the polymer support material; Fig. 2: Schematic representation of modification steps b.1 and b.2; Fig. 3: Schematic representation of modification steps b.1 and b.2 followed by exemplary modification steps c and d.1; Fig. 4: Schematic representation of an alternative modification step c or d.2; Fig. 5: Schematic representation of the result of a modification step d.1 followed by a reaction with BDGE (butanediol diglycidyl ether); Fig. 6: Schematic representation of an example of a reaction following step c or d.2 subsequent modification step e, introduction of an ion exchange group; Fig. 7: A chromatogram obtainable with a chromatography column according to embodiment 1 or 4; Fig. 8: Chromatograms obtainable with chromatography columns according to embodiment 1 or 4 with an increasing number of repetitions of modification step d; Fig. 9: Pressure-flow profile measured on a chromatography column according to the invention; Fig. 10: Chromatograms obtainable with chromatography columns according to embodiment 1 or 4 with an increasing duration of step f; Fig. 11: Pressure-flow profile measured on a chromatography column filled with polymer support material according to the invention from process step b.2; Fig. 12: Result of the particle size analysis by SEM (number versus diameter [µm]). Example 1:

[0072] All substances used were classified as "pure" or "pa" (with the exception of hydrogen peroxide and formic acid), solvents were separated from semi-volatile components by distillation on a rotary evaporator. Oxidation with potassium permanganate

[0073] 10.0 g of PS / DVB (55% DVB in EVB) were placed in a 350 mL sulfuring flask and suspended in 100 mL of acetonitrile. Then, 5.0 g of KMnO₄ dissolved in 100 mL of water were added dropwise over 20 minutes. The reaction solution was adjusted to an acidic pH with a small amount of acid. The suspension was stirred at 25 °C for 120 h. The particles were worked up with semi-concentrated hydrochloric acid and subsequently washed with ultrapure water. The product was dried to constant weight in a vacuum drying oven. The final weight was 9.7 g. Reduction with lithium aluminum hydride

[0074] 8.6 g of the dried, oxidized particles were placed in a 500 mL reactor and treated with 150 mL of THF. Under an argon atmosphere and external cooling to 5 °C, 1.5 g of lithium aluminum hydride was slowly added, followed by another 50 mL of THF. The reactor was heated to room temperature and stirred for 17 h. The reaction was stopped by the slow addition of water. The mixture was then worked up with a water / acetone solution, acidified with dilute sulfuric acid, and washed with water. After a final wash with acetone, the resulting solid was dried in a vacuum drying oven. 8.35 g of particles were obtained. react with epichlorohydrin (ECH)

[0075] 7.6 g of reduced, dried particles were placed in a 250 mL three-necked flask. 35 mL of epichlorohydrin were added, and the mixture was evacuated and vented with argon three times. The solution was heated to 45 °C. Then, 7 mL of the phase-transfer catalyst solution (3 g of tetrabutylammonium hydroxide in 10 mL of water) were added, followed by 140 mL of sodium hydroxide solution. The reaction was stirred for 3.5 hours and then stopped by the addition of water / ethanol. Work-up was carried out with water / ethanol and then water / acetone. The product was used directly in the next step without drying. react with butanediol

[0076] The polymer described above was then suspended at room temperature with 1.98 g of KOH in 70 mL of butanediol and subsequently stirred for 18 h at 130 °C. After completion of the reaction time, the reaction mixture was treated with water and filtered. The polymer was washed several times with water and acetone. The filter cake was dried overnight in a vacuum drying oven. 7 g of polymer were obtained. Attaching a spacer

[0077] 6.6 g of the above polymer were suspended in 16.5 mL DMSO and 16.5 mL butanediol diglycidyl ether, evacuated three times, and then aerated. Subsequently, 1.4 mL of 1 M tetrabutylammonium bromide solution and 16.5 mL of 0.6 M NaOH (aq) were added, and the mixture was mechanically stirred for 22 h. The reaction was stopped by adding a 1:1 mixture of water and ethanol. The mixture was washed several times with a water / ethanol mixture. Finally, the product was filtered to dryness. The polymer was then used directly in the next step. Introduction of anion exchange groups

[0078] The polymer described above was then suspended in 45 mL of DMSO without transition and subsequently mixed with 45 mL of water. The suspension was heated to 70 °C and 45 mL of N-methylpyrrolidine was added. After a reaction time of 2 h, the reaction was stopped by the addition of acetic acid. The polymer was filtered and washed several times with water. The moist polymer was used directly in the next step. Elimination

[0079] The polymer described above was suspended in 50 mL of water and treated with 7.5 mL of 40% NaOH (aq). The suspension was then stirred for 4 h at 100 °C. The reaction was stopped by filtration. The filter cake was washed several times with ultrapure water and then packed into a 4x100 mm PEEK column using established high-pressure packing methods. Example of implementation 2: Low-pressure oxygen plasma oxidation

[0080] 40 g of PS / DVB (55% DVB in EVB) were oxidized in a plasma powder system using oxygen plasma. The particles can be processed directly after treatment. Reduction with lithium aluminum hydride (LAH)

[0081] 30 g of the oxidized, dried polymer were suspended in 250 mL of dry diethyl ether in a 1000 mL pressure-equalized reactor. While heated to 25 °C under an argon atmosphere, 6 g of lithium aluminum hydride were slowly added, the mixture was heated to 30 °C for 6 h with stirring, and then stirred for a further 20 h at room temperature. The reaction was stopped by cooling the mixture to 0 °C and slowly adding 15 mL of ethyl acetate dropwise. The mixture was then worked up with water, dilute sulfuric acid, water, 5 wt% NaOH solution, ultrapure water, and dilute hydrochloric acid.

[0082] The polymer was washed neutrally with ultrapure water and dry-filtered with acetone. The product was dried in a vacuum drying oven. 30 g of polymer were obtained. react with epichlorohydrin

[0083] 5.0 g of reduced, dried particles were placed in a 250 mL three-necked flask and mixed with 25 mL of epichlorohydrin. The suspension was evacuated three times and vented with argon. Subsequently, 1.75 1 mL of the 1 M phase-transfer catalyst solution (tetrabutylammonium bromide in water) and 25 mL of 30% sodium hydroxide solution were added, heated to 45 °C, and stirred for 3.5 hours. The reaction was stopped by adding water / ethanol. The product was purified by repeated washing with water / ethanol or water / acetone. The product was used directly in the next stage without drying. react with butanediol

[0084] The polymer described above was then suspended at room temperature with 1.3 g of KOH in 50 mL of butanediol and heated to 130 °C for 18 h. After completion of the reaction time, the reaction mixture was diluted with 200 mL of water and filtered. The filter cake was washed with water and acetone. The product was dried in a vacuum drying oven, yielding 4.2 g of dry product. Attaching a spacer

[0085] 3.8 g of the above polymer were suspended in 10 mL DMSO and 10 mL butanediol diglycidyl ether and subjected to three pressure cycles, with the reaction vessel being refilled with argon. Then, 0.8 mL of 1 M tetrabutylammonium bromide solution and 10 mL of 0.6 M NaOH (aq) were added and the mixture was stirred for 22 h. Subsequently, the reaction mixture was treated with 200 mL of a 1:1 mixture of water and ethanol and filtered. This washing process was repeated several times, the product was filtered to dryness, and used directly in the next step. Introduction of ion exchange groups

[0086] The polymer described above was suspended in 30 mL of DMSO, 30 mL of water were added, and the suspension was heated to 70 °C. Upon reaching the reaction temperature, 30 mL of N-methylpyrrolidine was added, and the mixture was stirred for 2 h at 70 °C. After completion of the reaction time, 60 mL of concentrated acetic acid were added, and the product was filtered off. The filter cake was washed with neutral water and used in the elimination step. Elimination

[0087] The polymer described above was suspended in 100 mL of water, mixed with 20 mL of 30% NaOH (aq), and stirred at 100 °C for 28 h. After the reaction time had elapsed, the reaction was stopped by adding hydrochloric acid, the suspension was filtered, the filter cake was washed several times with neutral water, and then packed into a 4x100 mm PEEK column using known high-pressure packing methods. Example 3: Oxidation with meta-chloroperbenzoic acid

[0088] 20 g of PS / DVB (55% DVB in EVB) were placed in a 250 mL glass bottle with a screw cap and suspended with 93 g of dichloromethane. Then, 5.5 g of meta-chloroperbenzoic acid were added as a solid, and the reaction mixture was mixed on a shaker at room temperature for 18 h. The product was washed several times with ethanol and water and dried to consistency by weight in a vacuum drying oven. The final weight was 19.0 g. Hydrolysis with hydrochloric acid

[0089] 19 g of the oxidized, dried polymer were placed in a 250 mL glass bottle with a screw cap and suspended in 52 g of acetone and 13 g of 37% hydrochloric acid. The reaction mixture was mixed at 40°C on a forced-air heating shaker for 21 h. The product was washed with neutral water, then repeatedly with water and acetone, and dried to constant weight in a vacuum drying oven. The final weight was 18.5 g. react with epichlorohydrin

[0090] 11.8 g of the hydrolyzed, dried polymer were suspended in a 250 mL three-necked flask with 60 mL of epichlorohydrin. The reaction vessel was subjected to three vacuum / argon cycles. The reaction mixture was heated to 45°C with stirring, and then 3 mL of 1 M (aq) tetrabutylammonium bromide solution were added. Subsequently, 60 mL of 30% (aq) sodium hydroxide solution were added and stirred vigorously. After 22 h of reaction time, the reaction mixture was diluted with 200 mL of water and 200 mL of ethanol, and then the polymer was filtered off. The polymer was washed with acetone, water, and then acetone again. react with butanediol

[0091] 5 g of the above product were suspended in a 100 mL three-necked flask with 1.4 g of potassium hydroxide and 50 mL of 1,4-butanediol and mixed for 19 h at 130°C. The reaction mixture was then cooled and mixed with 45 mL of water. The product was filtered and washed with water to neutrality, then dried in a vacuum drying oven to a consistency determined by weight. The final weight was 4.0 g. Reaction with 1,4-butanediol diglycidyl ether

[0092] 3.1 g of the above product were suspended in a 100 mL three-necked flask with 8 mL of dimethyl sulfoxide and 8 mL of 1,4-butanediol diglycidyl ether. The reaction vessel was subjected to three vacuum / argon cycles. With stirring, 0.8 mL of 1 M (aq) tetrabutylammonium bromide solution and 8 mL of 0.6 M sodium hydroxide solution were added to the reaction. After 22 h of reaction time, the reaction mixture was treated with 25 mL of water and 25 mL of ethanol and then filtered. The product was washed once with water and ethanol. Introduction of ion exchange groups

[0093] The above product was suspended in a 100 mL three-necked flask with 15 mL dimethyl sulfoxide, 15 mL water, and 15 mL N-methylpyrrolidine. The reaction mixture was stirred for one hour at 70°C, then cooled and treated with 30 mL of acetic acid. The polymer was filtered off and washed with water. Elimination

[0094] The above product was suspended in a 100 mL round-bottom flask in 50 mL of water and 7.5 mL of 40% (aq) sodium hydroxide solution and heated to 100°C. After a reaction time of 4 h, the reaction mixture was cooled and filtered. The product was washed twice with water and then packed into a 4x100 mm PEEK column using known high-pressure packing methods. Example 4: Oxidation with formic acid

[0095] 25.0 g of PS / DVB (55% DVB in EVB) were suspended in 188 mL of formic acid in a 500 mL three-necked flask with pressure equalization. 54 mL of 35% hydrogen peroxide were slowly added via a dropping funnel, and the reaction solution was cooled externally. After the heat of reaction had dissipated, the mixture was stirred at room temperature for 65 h. Following this time, the reaction mixture was washed acid-free with ultrapure water and then dried in a vacuum drying oven until a constant weight was achieved. The final weight was 27.78 g. Reduction with lithium aluminum hydride

[0096] 27.64 g of the oxidized, dried polymer were suspended in 270 mL of dry diethyl ether in a 500 mL pressure-equalized 3-necked flask, cooled to 0 °C in an ice bath, and 8.8 g of lithium aluminum hydride were carefully added while stirring. After the addition, the ice bath was removed, and the reaction mixture was heated under reflux for 10 h while stirring, followed by 24 h at room temperature. The reaction was stopped by external cooling and the addition of diethyl ether, ethyl acetate, and ultrapure water. After the remaining hydride had reacted, the reaction mixture was placed on ice and stirred with dilute, cooled sulfuric acid. The reaction mixture was washed with the following solutions: water, 5% NaOH solution, water, dilute acetic acid, water, and acetone. The filter cake was filtered to dryness and dried in a drying oven. The yield was 26.20 g. react with epichlorohydrin

[0097] 4.00 g of the polymer were suspended in 20 mL each of ECH and DMSO, sonicated for 15 min in an ultrasonic bath, and then subjected to two pressure changes, with the reaction vessel being refilled with argon. After adding 4.30 mL of 25% tetramethylammonium hydroxide solution in water, the mixture was stirred for 2 h at room temperature. The reaction mixture was filtered and washed with a 1:1 mixture of water and 2-propanol with acetone. The filter cake was filtered to dryness. react with butanediol

[0098] The polymer described above was then suspended at room temperature with 1.12 g of KOH in 40 mL of butanediol and subsequently stirred for 20 h at 120 °C. After completion of the reaction time, the reaction mixture was washed several times with water and acetone. The product was filtered to dryness. The wet mass was 13.36 g. Coating cycle: Reaction with epichlorohydrin (ECH)

[0099] The still-moist polymer from the previous step was made up to 13.50 g with water, and 1 mL of 1M tetrabutylammonium bromide and 20 mL of ECH were added. Then, 10.5 mL of 50% NaOH (aq) was added, and the mixture was stirred for 5.5 h. The reaction mixture was then washed with a 1:1 mixture of water and 2-propanol, as well as acetone. The filter cake was filtered to dryness. Coating cycle: Reaction with butanediol

[0100] The polymer above was suspended in 40 mL of butanediol along with 1.12 g of KOH at room temperature and then stirred at 120 °C for 18 h. After completion of the reaction time, the mixture was washed several times with water and acetone. The product was filtered to dryness. Finally, the polymer was dried before further reaction. The yield was 5.66 g. Attaching a spacer

[0101] 2.30 g of the above polymer were suspended in 6 mL DMSO and 6 mL butanediol diglycidyl ether and subjected to three pressure changes, with the reaction vessel being refilled with argon. While stirring, 0.5 mL of 1 M tetrabutylammonium bromide solution and 6 mL of 0.6 M NaOH (aq) were added and the mixture was stirred for 22 h. The reaction mixture was then washed with a 1:1 mixture of water and 2-propanol and filtered to dryness. Introduction of anion exchange groups

[0102] The polymer described above was suspended in 5 mL of DMSO and treated with 5 mL of water and 5 mL of N-methylpyrrolidine. The reaction mixture was then stirred at 70 °C for 1 h. The reaction was stopped by adding water and dilute acetic acid. The filter cake was then washed with dilute hydrochloric acid, water, and acetone. The resulting polymer was dried in a drying oven at 60 °C. The yield was 2.54 g. Elimination

[0103] The polymer described above was suspended in 50 mL of water, mixed with 5 mL of 30% NaOH (aq), and stirred for 2 h at 100 °C. The reaction was stopped by filtration and subsequent washing with water, dilute HCl, water, and acetone. The filter cake was filtered to dryness, and the polymer was then dried at 60 °C in a drying oven. No significant weight loss was observed.

[0104] Figure 1Figure 1 schematically shows various exemplary modification sequences of the core polymer support material (pDVB). After initial oxidation (b.1) and subsequent reduction (alternatively: subsequent hydrolysis, b.2), a polymer support material is available that has hydroxyl groups on its surface (pDVB-OH). The polymer support material with OH groups (pDVB-OH) can then be reacted with epichlorohydrin (ECH). This results in a compound according to step c. Alternatively, the polymer support material with OH groups (pDVB-OH) can also be reacted with butanediol diglycidyl ether (BDGE) in step c.

[0105] According to the invention, the polymer support material can be reacted with ECH, a diol, and subsequently again with ECH or BDGE in one or more coating cycles after step b.2 (steps c, d.1, d.2). For example, the polymer support material can also be reacted directly with BDGE after step b.2. This results in a modified polymer support material having suitable reactive functional groups on its surface. In the example shown, these are epoxy groups.

[0106] In principle, any combination of ECH / BDGE modifications in steps c and d.2, respectively, and any combination of diol reactions / hydrolyses in step d.1 are conceivable. However, as described above, it is preferred if a spacer molecule is inserted during the last coating cycle in d.2.

[0107] The in Figure 1The modified polymer support material shown is suitable for the subsequent introduction of ion exchange groups. The oxygen content on the surface of the modified polymer support material increases in the order of the variants listed in the previous section (variants from top to bottom in the figure). When ion exchange groups are introduced into the products, the resulting ion exchange material has an increasing hydrophilicity in the order of the listed variants. The increased hydrophilicity manifests itself, for example, in a reduced selectivity σ of NO₃ to Cl.

[0108] The Figures 2 to 6The illustrations are intended to demonstrate the process steps according to the invention and show the reaction sequences in a highly simplified manner. They do not claim to be exhaustive. The focus is on the respective modification of the polymer support material surface. The portion of the polymer support material that is not modified in the respective step is shown, for simplicity, as a spherical particle.

[0109] Figure 2Figure 1 schematically shows modification steps b.1 and b.2. After oxidation and reduction (alternatively: hydrolysis), a polymer support material with OH groups on its surface is provided. It is known to those skilled in the art that not only ketones can be formed in the oxidation step. Depending on the treatment, and especially in the case of treatment with KMnO₄, diols, diketones, or, as a decomposition product, dicarboxylic acids can also be formed in addition to ketones. Such processes and intermediates are covered by the claimed process and are not to be excluded by the examples shown in the figures.

[0110] Figure 3Figure 1 schematically shows modification steps b.1 and b.2, followed by exemplary modification steps c and d.1. In the variant shown, the compound used in step c, which has at least one first functional group reactive with hydroxyl groups and at least one second functional group reactive with amines and / or hydroxyl groups, is epichlorohydrin. In the variant shown, the polyfunctional compound used in step d.1, containing hydroxyl groups, is butanediol. The coating sequence consisting of the alternating reaction with epichlorohydrin and butanediol can be repeated as d.1 and d.2. The resulting particles are again abstracted according to the double arrow.

[0111] Figure 4Figure 2 schematically shows an alternative modification step c or d.2. The compound used in step c or d.2, which has at least one first functional group reactive with hydroxy groups and at least one second functional group reactive with ion exchange groups and / or hydroxy groups, is BDGE.

[0112] Implementation with BDGE can also involve one or more coating cycles, as described in Figure 3 Figure 5 schematically and exemplarily shows the result of a modification step d.1. After using ECH in step c, coating cycles were carried out using ECH in step d.2. After reaction with butanediol, the final step d.2 is then carried out using BDGE as a spacer. This results in a modified polymer support material with an oxygen content on the surface, which ceteris paribus is higher than in the schemes Fig. 3 / Fig. 4resulting carrier materials.

[0113] Figure 6 Figure 1 schematically shows an example of a modification step e following step c or d.2, namely the introduction of an ion exchange group. In the example shown, the ion exchange group is formed by quaternization of 1-methylpyrrolidine. After carrying out a modification according to the invention, a polymer support material results which has side chains on its surface, such as the one shown by way of example.

[0114] Figure 7Figure 1 shows a chromatogram obtained with a chromatography column according to embodiment 1 or 4. The x-axis shows the run time in minutes. The y-axis shows the conductivity in µS / cm. The dried substrate was packed into a 150 x 4 mm column. 6.0 mmol / L Na₂CO₃ and 1.0 mmol / L NaHCO₃ were used as eluents. The analytes of the standard solution are baseline separated from each other, with the elution order from left to right being fluoride, bromate, chloride, nitrite, bromide, chlorate, nitrate, azide, phosphate, sulfate. Bromate is quantifiably present before chloride (peaks at 5.2 and 5.7 minutes run time), and the chromatogram shows high signal symmetries. The total column run time is short at 15 minutes. Chromatography columns produced under the conditions of embodiment 1 yield a comparable chromatogram.

[0115] Figure 8Figure 1 shows three chromatograms obtained with a chromatography column according to embodiment 4. Embodiment 1 yields very similar chromatograms. The x-axis shows the runtime in minutes. The y-axis shows the conductivity in µS / cm. The curves show chromatograms of an identical standard solution, with the elution order from left to right being fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate. The number of repetitions of modification steps d.1 / d.2 was increased (from top to bottom). For the solid curve A, the step sequence d.1 / d.2 was performed once. For the dotted curve B, the step sequence d.1 / d.2 was performed twice. For the dashed curve C, the step sequence d.1 / d.2 was performed three times.Specifically, curve A shows a polymer substrate that underwent oxidative / reductive treatment, was treated once with ECH and then once with 1,4-butanediol, and subsequently reacted with BDGE. Curve B shows a polymer substrate that underwent oxidative / reductive treatment, was treated with ECH and then with 1,4-butanediol, then again with ECH and then with 1,4-butanediol, and subsequently reacted with BDGE. Curve C shows a polymer substrate that underwent oxidative / reductive treatment. The following step sequence then followed: reaction with ECH; 1,4-butanediol; ECH; 1,4-butanediol; ECH; 1,4-butanediol; BDGE. In all three cases, the modified substrate was subsequently reacted with methylpyrrolidine.The chromatograms show that the signals of the anions affected by tailing (nitrite, bromide, nitrate) gain in symmetry with an increasing number of coating cycles. The selectivity σ of NO₃ to Cl decreases with an increasing number of coating cycles. The overall capacity decreases.

[0116] Figure 9Figure 1 shows a pressure-flow profile measured on a chromatography column according to the invention, prepared according to Example 4, measured at room temperature. The y-axis shows the system pressure in MPa. The x-axis shows the flow rate in mL / min. Seventeen 20-minute intervals were measured with a stepwise increase in the flow rate from 1 mL / min to 2.6 mL / min. The pressure depends linearly on the flow rate. This contrasts with results obtained using conventional columns packed with hydrophilic pDVB substrate. With conventional columns, the pressure increases more than linearly with the flow rate. For example, the function may exhibit a hyperbolic slope.

[0117] Fig 10Figure 1 shows chromatograms obtainable with chromatography columns according to the invention, in particular with chromatography columns filled with modified polymer support material according to embodiment 1 or 4. The x-axis shows the run time in minutes. The y-axis shows the conductivity in µS / cm. The duration of step f was varied. The dried substrate was packed into a 100 x 4 mm column. The curves each show the chromatogram of an identical standard solution, with the elution order from left to right being fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate. From top to bottom, the curves show the chromatograms obtainable after elimination of the column substrate in step f for 0 min (A), 60 min (B), 120 min (C), 180 min (D), 240 min (E), and 300 min (F). If step f (0 minutes) is omitted, the nitrate peak and the phosphate peak overlap. The total capacity decreases with longer elimination time.The analytes are baseline-separated from each other, and the chromatogram shows high signal symmetries. The total column run time is short, approximately 14 to 20 minutes. Example 5: Determination of the average pore radius and the specific surface area of ​​the polymer support material provided in step a

[0118] In embodiment 1, a modification according to the invention is carried out on a PS / DVB (55% DVB in EVB). The starting polymer support material is both hydrophobic and microporous or mesoporous. The starting polymer support material is obtained as follows: Production of a polystyrene seed particle in a dispersion polymerization of styrene in ethanol, stabilized with polyvinylpyrrolidone and initiated with azobisisobutyronitrile. This yields a polystyrene particle with a diameter of 1.5 µm and MN = 15 kg / mol, MW = 55 kg / mol. The polystyrene particle thus obtained is then sourced in an emulsion of 55% divinylbenzene (DVB) / 45% ethylvinylbenzene (EVB) and toluene in water / isoamyl alcohol, stabilized with polyvinyl alcohol, followed by polymerization initiated by azobisisobutyronitrile. This results in a porous, highly cross-linked poly(DVB-co-EVB) particle with a radius of 5 µm and a porosity of 1 cm 3< / g.

[0119] The average pore radius of the starting polymer support material was determined by nitrogen sorption using the BJH (Barret, Joyner, Halenda) model. The specific surface area was determined by nitrogen sorption using the BET (Brunauer, Emmett, Teller) model. A 0.0945 g sample of PS / DVB polymer support material was used for both analyses. The density of the sample material was 1.05 g / cc. The measurement was performed on an Autosorb iQ S / N:14713051301 instrument in a 9 mm cell. The bath temperature was 77.35 K. The final outgassing temperature was 60 °C. The measurement was evaluated using Quantachrome ASi-Qwin version 3.01. The measurement was performed twice, once with a soaking time of 80 min and once with a soaking time of 40 min. The outgassing rate was 1.0 °C / min and 20.0 °C / min, respectively. The mean pore radius resulting from the BJH method based on the pore volume was 5,060 nm. The specific surface area according to the multi-point BET plot was 815.0 m² / g calculated. Example 6: Determination of the pressure stability of the polymer support material according to step b.2

[0120] In embodiment 4, a modification according to the invention is carried out on a PS / DVB (55% DVB in EVB). The starting polymer support material is obtained as described in Example 5. Oxidation with hydrogen peroxide and reduction with lithium aluminum hydride are performed on the starting polymer support material, both according to the specifications in Example 4, corresponding to the result of step b.2. The resulting particle was subjected to a pressure test. For the pressure test, a 250 x 4 mm column was packed with the resulting particle, and water was passed through the column at an increasing flow rate. Figure 11The figure shows a pressure-flow profile measured at room temperature. The y-axis represents the system pressure in bar. The x-axis represents the flow rate in mL / min. Eight 30-second intervals were measured, with the flow rate gradually increasing from 0.2 mL / min to 1.6 mL / min. As can be seen from the figure, the pressure depends linearly on the flow rate, up to pressures of 400 bar or 40 MPa. Example 7: Determination of the average particle size

[0121] The circularity and average particle diameter were determined for a sample of the starting polymer support material provided in step a. For this purpose, the sample was applied to a scanning electron microscope slide in a single particle layer and coated with gold using a LOT AutomaticSputterCoater MSC1 sputter coater connected to a Vacubrand RZ 6 vacuum pump. A series of 27 images was acquired using a scanning electron microscope (Phenom ProX), and the individual particles were identified and measured using Olympus Imaging Solutions Scandium. The identified particles were analyzed for spherical diameter and roundness. All images were analyzed in batch processing with identical thresholds and measurement settings. A total of 6039 particles were measured, with a circularity consistently ≥0.8. The measurement results are presented in Figure 12The graph shows the number of particles on the y-axis and the diameter in µm on the x-axis. The smallest measured radii were 0.8 µm, the largest up to 10 µm. The mean diameter (median) was 4.59 µm, with a relative standard deviation of 6.23%. The polydispersity index (PDI) (Mw / Mn) was 1.044. Example 8: Determination of pH stability

[0122] The pH stability was determined for a sample of particulate polymer support material according to Example 5, modified according to Example 4, i.e., corresponding to a polymer material obtainable according to steps a to f. For this purpose, the sample was packed into a chromatography column (250 x 4 mm) and the sulfate retention time was determined from ten measurements using an eluent of 6 mmol / L Na₂CO₃ and 1 mmol / L NaHCO₃. The column was then flushed for 14 h with an eluent of 6 mmol / L Na₂CO₃ and 1 mol / L NaOH (pH 14) at 0.8 mL / min. Ten more sulfate retention time measurements were then performed using an eluent of 6 mmol / L Na₂CO₃ and 1 mmol / L NaHCO₃. The column was then flushed for 14 h with an eluent of 6 mmol / L Na₂CO₃ and 1 mol / L HNO₃ (pH 0) at 0.8 mL / min. Ten more sulfate retention time measurements were then performed with an eluent of 6 mmol / L Na₂CO₃ and 1 mmol / L NaHCO₃.During each eluent change, the solution was rinsed with water for 1 hour to prevent precipitation. Any changes were investigated based on the retention time and sulfate plate values; both parameters deviated by a maximum of 3% from the originally determined values ​​after both basic and acidic treatment.

Claims

1. A method for modifying a polymer carrier material for use as a stationary phase in an analytical or preparative separation process, comprising the steps of a. Providing a polymer carrier material at least partially formed from aromatic hydrocarbon compounds having at least two vinyl or allyl substituents, preferably at least partially formed from divinylbenzene monomers; wherein the polymer support material provided has an average pore radius of 1 to 50 nm, preferably 2 to 25 nm, more preferably 2 to 10 nm, measurable by nitrogen sorption in the BJH model, and a specific surface area of 80 to 1000 m2 / g, preferably from 100 to 800 m2 / g, more preferably from 200 to 600 m2 / g, measurable by nitrogen sorption in the BET model; b. Production of hydroxyl groups on / in the polymer carrier material by a process comprising the steps b.1 oxidative treatment of the polymer carrier material, and then b.2 reductive or hydrolytic treatment of the reaction product from step b.1; c. Optional: reaction of the product from step b.2 with a polyfunctional compound, in particular a compound which - at least one first functional group that is reactive with hydroxy groups, preferably a halogen group, and - at least one second functional group that is reactive with amines and / or hydroxyl groups, preferably an epoxy group.

2. Method according to claim 1, comprising steps a, b, and c, wherein step c is followed by step d: d. performing a number of coating cycles comprising the steps d.1 introducing or generating hydroxyl groups by reacting the second functional group, preferably the epoxy group, introduced in step c, by - reacting with a polyfunctional compound containing hydroxyl groups, in particular reacting with a polyol, or - hydrolysis, or - a combination thereof; d.2 reacting the product from step d.

1. with a polyfunctional compound, in particular a compound which comprises - at least one first functional group that is reactive with hydroxyl groups, preferably a halogen group and - at least one second functional group that is reactive with amines and / or hydroxyl groups, preferably an epoxy group; wherein the number of coating cycles is between 0 and 20.

3. Method according to claim 1, comprising steps a, b, and c, or according to claim 2, additionally comprising the step: e. Introduction of ion exchange groups onto the reaction product from step c or d.2.

4. Method according to one of claims 1 to 3, characterized in that the oxidative treatment in step b.1 is a treatment with a peracid, preferably selected from the group consisting of meta-chloroperbenzoic acid, peroxyformic acid, peracetic acid, peroxytrifluoroacetic acid, a treatment with KMnO4, treatment with oxygen plasma, or a combination thereof.

5. Modified polymer carrier material for use as a stationary phase in an analytical or preparative separation process, in particular a chromatography process, obtainable by a process according to one of claims 1 to 4, wherein the polymer carrier material provided in step a. has an average pore radius of 1 to 50 nm, preferably 2 to 25 nm, particularly preferably from 2 to 10 nm, measurable by nitrogen sorption in the BJH model, and a specific surface area of 80 to 1000 m2 / g, preferably from 100 to 800 m2 / g, even more preferably from 200 to 600 m2 / g, measurable by nitrogen sorption in the BET model.

6. Modified polymer carrier material according to claim 5, wherein the polymer carrier material provided in step a is composed of at least 95% by weight of monomer units selected from the group of: - monomer units derived from aromatic hydrocarbon compounds having at least two vinyl or allyl substituents, preferably derived from divinylbenzene; - monomer units derived from ethylvinylbenzene; - monomer units derived from styrene; - a combination thereof.

7. Modified polymer carrier material according to one of claims 5 to 6, wherein the material is preferably in the form of particles, preferably spherical particles, particularly preferably spherical particles with an average particle size of 1 to 50 µm, even more preferably with an average particle size of 2 to 25 µm, particularly preferably with an average particle size of 3 to 9 µm.

8. Modified polymer carrier material according to one of claims 5 to 7, wherein the material is stable in the pH range from 0 to 14, in particular the retention time of sulfate in a column packed with modified polymer carrier material after rinsing with 1M NaOH solution and / or rinsing with 1M HNO3solution is not more than 8%, preferably not more than 5%, particularly preferably not more than 3%, from the retention time of sulfate in a column packed with modified polymer carrier material that has not previously been exposed to pH values of 0 to 14.

9. Chromatography column, in particular ion exchange chromatography column, packed with modified polymer carrier material according to one of claims 5 to 8.

10. Method for the chromatographic separation of analytes, characterized in that a solution containing the analytes is contacted with modified polymer carrier material according to claims 5 to 8, in particular is passed through a chromatography column according to claim 9.

11. Use of the polymer carrier material according to one of claims 5 to 8 for the analytical or preparative separation of analytes, in particular use in anion exchange chromatography, cation exchange chromatography, and / or HILIC chromatography.