GB2194900A

GB2194900A - High performance anion-exchange chromatographic packing composition

Info

Publication number: GB2194900A
Application number: GB8622065A
Authority: GB
Inventors: Timothy S Stevens; Martin A Langhorst; Iii Osro W Randall
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1986-09-12
Filing date: 1986-09-12
Publication date: 1988-03-23
Anticipated expiration: 2006-09-12
Also published as: FR2604525A1; DE3632404A1; GB8622065D0; GB2194900B; FR2604525B1

Abstract

An anion-exchange chromatographic packing composition has a substrate which comprises particles of from 1 to 75 micrometers diameter and having cation-exchanging sites at least on their available surfaces. The particles have a liquid coating which comprises a hydrophilic, water-soluble, film-forming resin having anion-exchanging sites which attract available cation-exchanging sites of the substrate, whereby the liquid coating is retained by electrostatic bonds on the available surfaces of the substrate particles. <IMAGE>

Description

SPECIFICATION High performance anion-exchange chromatographic packing composition The invention relates to a high performance anion-exchange chromatographic packing composition.

More particularly, the invention resides in an anion-exchanging packing composition comprising a hydrophilic, water-soluble, film-forming resin. The resin has anion-exchanging sites which attract the available sites of its substrate particles and thereby form a liquid coating on the available surfaces of the particles.

Since the inception of ion chromatography (U.S. Patent 3,920,397), the basic technology for the anion-exchanger used in the analytical column for anion determination has not changed. Solid microparticles of anion-exchanger are agglomerated with macroparticles of surface sulfonated or fully suifonated styrene divinylbenzene copolymer to produce a low capacity "pellicular type" anion-exchanger (U.S. Patent 4,101,460).

Improvements within this basic technology came with the use of monodisperse anion-exchange latex rather than the previously used ground anion-exchange resins (as described in the '460 patent), and by performing an agglomeration step in a polyvalent salt solution (U.S. Patent 4,119,580). The use of monodisperse anion-exchange latex eliminated the problem of refining ground ion-exchange resin to obtain the desired size range, while agglomerating in a polyvalent salt solution resulted in a reproducible and dense deposition of microparticles due to the resulting suppression of the anionic repulsion forces between the microparticles.

A further improvement is disclosed in U.S. Patent 4,383,047 wherein the use of smaller diameter latex microparticles is described. Anion-exchangers of this type achieve a performance level in which baseline separation of fluoride, chloride, nitrite, phosphate, bromide, nitrate, and sulfate ions is completed in about 6 minutes (illustrated by the chromatogram in Figure 3 of the '047 patent).

Throughout these developments in the technology the packing compositions have been limited to eluent insoluble resins for both the agglomerated and substrate components. There has not been any suggestion that other types of components could be useful or practicable.

The invention particularly resides in a chromatographic analytical column containing an anionexchange chromatographic packing comprising: a substrate of non-swelling particles having cation-exchanging sites at least on their available surfaces, the particles having a diameter of from 1 to 75 micrometers (cm); and a chromatographically active anion-exchange liquid coating irreversibly attached to the available surfaces of the particles, the liquid coating comprising a hydrophilic, water-soluble, film-forming aminated resin having anion-exchanging sites which attract available cation-exchanging sites on the particles, wherein the liquid coating is retained by electrostatic bonds on the available surfaces of the particles.

The invention also resides in a process for chromatographic separation of diverse anions comprising the steps of: passing a liquid solution comprising the anions through a bed of non-swelling particles having cation-exchanging sites at least on their available surfaces, the particles having a diameter of from 1 to 75 ijm, and a chromatographically active anion-exchange liquid coating irreversibly attached to the available surfaces of the particles, the liquid coating comprising a hydrophilic, water-soluble, film-forming aminated resin having anion-exchanging sites which attract available cation-exchanging sites on the particles, wherein the liquid coating is retained by electrostatic bonds on the available surfaces of the particles, and wherein anion-exchanging sites at least on the surface of the liquid coating attract at least one of said anions; and eluting the bed with an eluent which differentially removes the attracted anions from the bed.

Figure 1 reproduces an actual chromatogram developed by the high performance packing composition of one embodiment of this invention.

According to the present invention substrate particles, typically resin beads, serve to firmly retain a liquid coating which includes active anion-exchange sites used for chromatographic separation. Each substrate particle is insoluble in the solvent systems used for separation. They are suitably formed of resin beads, preferably substantially spherical in shape, of from 1 to 75 ,lim in diameter, preferably from 3 to 20 m. Highly preferred for use in the invention are particles having a diameter from 4 to 10 ,um.

Suitable compositions for the substrate particles are well known in the art and are discussed in detail in U. S. Patent 4,351,909 and in U. S. Patent 4,383,047. In the present invention, the particles may be "macroporous" as described in the '909 patent, resulting in chromatographic columns having higher capacities but longer analysis times, or the particles preferably may be of low porosity, as described in the '047 patent, to yield columns having shorter analysis times.

Particles having low porosity are known in the art as gel type resins and are exemplified by the DOWEXB 50W ion-exchange resins. As in both of the references cited, the substrate particles preferably are monodisperse with respect to their diameters.

Due to the nature of the electro-static bonds which form with the liquid coating, the available surfaces of the substrate particles preferably are relatively "hard" rather than swollen. This means that substrate particles of the gel type resins should have a relatively high degree of crosslinking. Good results have been achieved with crosslinking of about 35 percent within the particles.

Glass or silica beads, also known in the art as suitable substrate particles, provide the "hard" surfaces of the preferred particles. Basic eluents, however, have been found to remove the liquid coating on glass beads. In practicing the invention, therefore, glass beads may be used for the substrate except where a basic eluent, having a pH of about 8 or more, will be used with the packing composition, in which case a synthetic resin is preferred.

Among suitable materials for the anion-exchange liquid coating are the well known water soluble aminated poly(vinylaromatic) resins such as the quaternary ammonium electroconductive resins discussed in detail in U.S. Patent 3,887,496 (in particular, at column 2, lines 34-47).

Preferred for use are poly(vinylaromatic) resins having anion-exchanging sites substantially throughout the entirety of a majority of the polymer chains. The anion-exchanging sites may be either strong base, generally quaternary ammonium functional groups, or weak base, generally tertiary, secondary and primary amine functional groups.

Column Preparation Columns using the packing compositions of the invention are desirably prepared by first efficiently packing the column with the substrate particles, and then adding a solution of the liquid coating resin using an in situ coating method. The amount of resin which coats onto the substrate particles by electrostatic attraction is self-limiting and the excess resin will wash out of the column.

To assure a proper bonding between the substrate and the liquid coating, the substrate particles should not contact any surfactants or other agents which could interfere with the electrostatic attraction between the coating and substrate particles. The particles should be thoroughly cleansed of any such surfactant or agent if contact cannot be avoided.

The invention, in its broadest sense, additionally embraces alternative methods for preparing the packed column or packing composition described. Such alternate methods are disclosed in U.S. Patent 4,119,580 and U.S. Patent 4,101,460 wherein the substrate particles are added to a solution of the liquid coating resin in an aqueous solution of a polyvalent salt, followed by a conventional column packing procedure using the precoated packing resulting from this preparation.

The anion-exchange compositions of the present invention have been found to be stable. The liquid coating is irreversibly attached to the available surfaces of the substrate particles such that a substantial amount of the coating will not be displaced by eluents normally used in the art, such as electrolyte solutions of 0.1 M or less. Shearing forces, such as those encountered when a liquid passes through an ion-exchange bed at elevated flow rates, also will not displace a substantial amount of the liquid coating.

Chromatographic Conditions The following chromatographic conditions were used to evaluate the packed chromatographic column described in the example, below.

Column: 9 x 242 mm, 10-20 Mm DOWER SOW X 35 treated with quaternized polystyrene Eluent: 0.0024 molar Na;CO 0.003 molar NO3 Flow Rate: 138 mi/hour Stripper Column: 2.8 x 300 mm DOWEXR 50W X 16, H form resin 200r400 mesh Injection Volume: 50 microliter loop Detection: conductivity at 7.5 Mho cm 1 full scale deflection Sample Standard The following seven ion standards were used as a 4X dilution: F 3.3 ppm Cl 4 ppm NO2 10 ppm PO43 54 ppm Br 10 ppm NO3 34 ppm so4= 50 ppm The above conditions and standard solutions are widely used for the evaluation of ion chromatographic analytical columns (see U.S. Patent 4,119,580).

Example To compare the performance of one embodiment of the present invention to that of columns already known in the art, a "suction packed" column was prepared with the substrate as described above on which a water soluble aminated polystyrene resin was coated. The packing method used is described in detail in U. S. Patent 4,383,047.

An actual chromatogram which resulted from the use of the column of this example is reproduced in Figure 1. This Figure clearly indicates that the column achieved good separation of the components of the seven ion standard solutions within approximately seven minutes.

Claims

1. A chromatographic analytical column containing an anion-exchange chromatographic packing comprising: a substrate of nonswelling particles having cation-exchanging sites at least on their available surfaces, the particles having a diameter of from 1 to 75 micrometers; and a chromatographically active anion-exchange liquid coating irreversibly attached to the available surfaces of the particles, the liquid coating comprising a hydrophilic, water-soluble, film-forming aminated resin having anion-exchanging sites which attract available cation-exchanging sites on the particles, wherein the liquid coating is retained by electrostatic bonds on the available surfaces of the particles.

2. A packed column as claimed in Claim 1, wherein said particles have a diameter from 3 to 20 micrometers.

3. A packed column as claimed in Claim 2, wherein said particles have a diameter from 4 to 10 micrometers.

4. A packed column as claimed in any one of the preceding claims, wherein the particles are monodisperse.

5. A packed column as claimed in any one of the preceding claims, wherein said liquid coating is a water-soluble aminated poly(vinylaromatic) resin.

6. A packed column as claimed in any one of the preceding claims, wherein said particles are insoluble synthetic resin particles.

7. A packed column as claimed in Claim 6, wherein said insoluble synthetic resin particles are of the gel type.

8. A packed column as claimed in any one of Claims 1 to 5, wherein said particles are silica or glass beads.

9. A packed column as claimed in Claim 1 and substantially as hereinbefore described in the Example.

10. A process for chromatographic separation of diverse anions comprising the steps of: passing a liquid solution comprising the anions through a bed of nonswelling particles having cation-exchanging sites at least on their available surfaces, the particles having a diameter of from 1 to 75 micrometers, and a chromatographically active anion-exchange liquid coating irreversibly attached to the available surfaces of the particles, the liquid coating comprising a hydrophilic, water-soluble, film-forming aminated resin having anion-exchanging sites which attract available cation-exchanging sites on the particles, wherein the liquid coating is retained by electrostatic bonds on the available surfaces of the particles, and wherein anion-exchanging sites at least on the surface of the liquid coating attract at least one of said anions; and eluting the bed with an eluent which differentially removes the attracted anions from the bed.

11. A process as claimed in Claim 10, wherein said particles and/or resin are as defined in any one of Claims 1 to 7.

12. A process as claimed in Claim 8, wherein the particles/d're selected from silica and glass beads and the pH of the eluent is less than 8.

13. A process as claimed in Claim 10 and substantially as hereinbefore described in the Example.

14. An ion-exchange process comprising the use of a water soluble polymer having anionexchange functional groups and an ion-exchange functional substrate which is an insoluble particle.