EP0309489A4 - Fused-silica microbore packed chromatography column with chemically modified column wall. - Google Patents

Fused-silica microbore packed chromatography column with chemically modified column wall.

Info

Publication number
EP0309489A4
EP0309489A4 EP19870907262 EP87907262A EP0309489A4 EP 0309489 A4 EP0309489 A4 EP 0309489A4 EP 19870907262 EP19870907262 EP 19870907262 EP 87907262 A EP87907262 A EP 87907262A EP 0309489 A4 EP0309489 A4 EP 0309489A4
Authority
EP
European Patent Office
Prior art keywords
column
stationary phase
wall
microbore
silica
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19870907262
Other languages
German (de)
French (fr)
Other versions
EP0309489A1 (en
Inventor
Frank J Yang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Varian Medical Systems Inc
Original Assignee
Varian Associates Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Varian Associates Inc filed Critical Varian Associates Inc
Publication of EP0309489A1 publication Critical patent/EP0309489A1/en
Publication of EP0309489A4 publication Critical patent/EP0309489A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/60—Construction of the column
    • G01N30/6052—Construction of the column body
    • G01N30/6073—Construction of the column body in open tubular form
    • G01N30/6078—Capillaries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
    • B01D15/10—Selective adsorption, e.g. chromatography characterised by constructional or operational features
    • B01D15/20—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to the conditioning of the sorbent material
    • B01D15/206—Packing or coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
    • B01D15/10—Selective adsorption, e.g. chromatography characterised by constructional or operational features
    • B01D15/22—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to the construction of the column
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/50—Conditioning of the sorbent material or stationary liquid
    • G01N30/52—Physical parameters

Definitions

  • Microbore chromatography columns i.e., columns having an inner diameter of approximately .6 mm or less, are becoming an increasing important tool in modern liquid chromatography.
  • Fused-silica is the preferred material for fabricating such columns because its properties offer many advantages over available alternative materials.
  • Fused-silica is flexible, strong, able to withstand high pressure, optically transparent, and has very good chemical inertness.
  • columns made of fused-silica have very smooth inner walls which minimizes wall effects.
  • stainless steel tubing also commonly used in chromatography, has relatively rough surfaces which exacerbate wall effects.
  • Fused-silica microbore columns may be packed, as shown for example in the inventor's prior U.S. Pat. No. 4,483,773, or left open, as shown, for example, in the articles "Open Tubular Column LC: Theory and Practice,” vol.20, pp. 241 et seq., Journ. of Chrom. Science (1982), by the inventor; and "Contemporary Capillary Column Technology for Chromatography,” May-June 1986 Chromatography Forum, pp. 38 et seq., by Jones, et al. As described in these articles and in the referenced patent, both types of columns, i.e., packed and open, may be used in either gas or liquid chromatography.
  • the stationary phase provides the partition medium for separating sample components and should be selected from a variety of substances according to the intended use of the column.
  • Fused silica is chemically similar to the silica substrates used in traditional LC packings and, accordingly, similar stationary phase materials may be used.
  • the stationary phase layer will typically have a thickness of between .1 to 5 ⁇ m . The methods for surface deactivation and chemical bonding of stationary phase materials are well known in the art and will not be further described.
  • fused-silica columns have very smooth inner walls which tends to minimize wall effects.
  • fused-silica columns it has traditionally been thought that the column walls played no significant role in the operation of the column. Accordingly, in the past, no effort has been made to deactivate or chemically modify the column wall of a packed fused-silica microbore column.
  • the present invention comprises a packed fused-silica microbore column with a deactivated and/or chemically modified column wall.
  • the chemical modification of the column wall can be used to modify and improve the performance of the column in a variety of ways.
  • the stationary phase bonded to the column wall may be different than the stationary phase bonded to the packing material. When this is done column performance may be greatly enhanced for reasons which are not fully understood as yet.
  • Figure 1 is a cross-sectional view of a portion of a microbore packed column in accordance with the present invention.
  • Figure 2 is a chromatogram obtained using a packed microbore column having a stationary phase bonded to the inner wall in accordance with the present invention.
  • FIG. 1 a portion of a fused-silica microbore column (10) of the present invention is shown in cross-section.
  • the column comprises a fused-silica microbore tube (15).
  • microbore is used to denote that the tube has an inner diameter less than approximately .6 mm.
  • Column length may vary considerably depending on the application and needs of the chromatographer. Lengths ranging from 10 cm to 200 cm are typical. The manner of construction of such fused-silica microbore tubes is well known in the art and will not be described further.
  • a stationary phase (20) is chemically bonded to the inner wall of the fused-silica tube (15).
  • the inner wall Prior to bonding of the stationary phase (20), the inner wall should, preferably, be deactivated using methods well known to those skilled in the art of making open tubular fused-silica columns.
  • a stationary phase such as methylphenylsiloxane, dimethylpolysiloxane, polyethylene glycol, dimethyldiphenylpolysiloxane, octadecylsiloxane, octylsiloxane, aminopropylsiloxane, propylsiloxane, cyanopropylsiloxane, cation or anion exchanger siloxanes, liquid crystals, etc., may be selected according to the specific application need. Methods of bonding the selected stationary phase are well known to those skilled in the art of making open tubular fused-silica columns.
  • the resulting stationary phase layer (20) may range in thickness from .1 to 5 ⁇ m. However, as noted below, a relatively thin layer (in the 0.1-1.0 range may be preferred.
  • the column is filled with packing material (25) comprising microparticulate silica.
  • packing material comprising microparticulate silica.
  • a selected stationary phase (not shown) is bonded to the micro-particulate silica prior to packing.
  • the packing should preferably consist of substantially uniform particles having a diameter in the range of 1 to 200 ⁇ m. The method of packing a microbore fused-silica column is described in the inventor's U.S. Pat. No. 4,483,773.
  • the stationary phase selected for the packing material be the same as the stationary phase (20) bonded to the column wall. Indeed, there may be distinct advantages to selecting a stationary phase for the wall that is different than the stationary phase of the packing material. It appears experimentally that, by selecting appropriate surface modification chemicals one can minimize surface adsorption sites and modify physicochemical interaction between solute molecules and the active sites on the column wall, adding one more parameter for control of chromatographic processes.
  • the scope of chemical modification of the surface of the inner wall may include, for example:
  • Table 1 shows the chromatographic characteristics of relative retention between toluene and benzene and total plate count for anthracene for a four different columns. Three of the columns were prepared according to the present invention and compared to a untreated fused-silica column of the prior art. Relative retention, ⁇ , between toluene and benzene increases for the chemically modified columns ( ⁇ 1.52) compared to the untreated column ( ⁇ 1.41). This increase in relative retention suggests a significant intermolecular interaction between solute molecules and the stationary phase on the column wall.
  • the plate count for the untreated column is 71,000 plates/m for anthracene. After a 5% phenylmethylsiloxane modification of the column wall, the plate count is reduced to 39,000 for a 0.25 ⁇ m film and to 23,000 for a 1.0 ⁇ m film.

Abstract

A packed, microbore fused-silica column (10) for use in liquid chromatography, wherein the column wall has been chemically modified, is shown. The chemical modification of the column wall is used to modify and improve the performance of the column (10). In one embodiment a stationary phase (20), different than the stationary phase bonded to the packing material (25), is bonded to the column wall. For reasons that are not yet understood column performance may be greatly enhanced.

Description

FUSED-SILICA MICROBORE PACKED CHROMATOGRAPHY COLUMN WITH CHEMICALLY MODIFIED COLUMN WALL
Background of the Invention Microbore chromatography columns, i.e., columns having an inner diameter of approximately .6 mm or less, are becoming an increasing important tool in modern liquid chromatography. Fused-silica is the preferred material for fabricating such columns because its properties offer many advantages over available alternative materials. Fused-silica is flexible, strong, able to withstand high pressure, optically transparent, and has very good chemical inertness. Moreover, columns made of fused-silica have very smooth inner walls which minimizes wall effects. In contrast, stainless steel tubing, also commonly used in chromatography, has relatively rough surfaces which exacerbate wall effects.
Fused-silica microbore columns may be packed, as shown for example in the inventor's prior U.S. Pat. No. 4,483,773, or left open, as shown, for example, in the articles "Open Tubular Column LC: Theory and Practice," vol.20, pp. 241 et seq., Journ. of Chrom. Science (1982), by the inventor; and "Contemporary Capillary Column Technology for Chromatography," May-June 1986 Chromatography Forum, pp. 38 et seq., by Jones, et al. As described in these articles and in the referenced patent, both types of columns, i.e., packed and open, may be used in either gas or liquid chromatography.
When making fused-silica microbore columns for open tubular chromatography it is necessary to deactivate the inner column wall and then to chemically bond a uniform layer of a stationary phase to the surface of the wall. The stationary phase provides the partition medium for separating sample components and should be selected from a variety of substances according to the intended use of the column. Fused silica is chemically similar to the silica substrates used in traditional LC packings and, accordingly, similar stationary phase materials may be used. The stationary phase layer will typically have a thickness of between .1 to 5 μm . The methods for surface deactivation and chemical bonding of stationary phase materials are well known in the art and will not be further described. See, e.g., "Contemporary Capillary Column Technology for Chromatography," cited above, for an overview of these methods. As has already been noted, fused-silica columns have very smooth inner walls which tends to minimize wall effects. For packed microbore fused-silica columns it has traditionally been thought that the column walls played no significant role in the operation of the column. Accordingly, in the past, no effort has been made to deactivate or chemically modify the column wall of a packed fused-silica microbore column.
Summary of the Invention
The present invention comprises a packed fused-silica microbore column with a deactivated and/or chemically modified column wall. The chemical modification of the column wall can be used to modify and improve the performance of the column in a variety of ways. The stationary phase bonded to the column wall may be different than the stationary phase bonded to the packing material. When this is done column performance may be greatly enhanced for reasons which are not fully understood as yet. Brief Description of the Drawing
Figure 1 is a cross-sectional view of a portion of a microbore packed column in accordance with the present invention. Figure 2 is a chromatogram obtained using a packed microbore column having a stationary phase bonded to the inner wall in accordance with the present invention.
Detailed Description of the Invention
In Figure 1 a portion of a fused-silica microbore column (10) of the present invention is shown in cross-section. The column comprises a fused-silica microbore tube (15). The term microbore is used to denote that the tube has an inner diameter less than approximately .6 mm. Column length may vary considerably depending on the application and needs of the chromatographer. Lengths ranging from 10 cm to 200 cm are typical. The manner of construction of such fused-silica microbore tubes is well known in the art and will not be described further.
In the preferred embodiment of the present invention, a stationary phase (20) is chemically bonded to the inner wall of the fused-silica tube (15). Prior to bonding of the stationary phase (20), the inner wall should, preferably, be deactivated using methods well known to those skilled in the art of making open tubular fused-silica columns. A stationary phase such as methylphenylsiloxane, dimethylpolysiloxane, polyethylene glycol, dimethyldiphenylpolysiloxane, octadecylsiloxane, octylsiloxane, aminopropylsiloxane, propylsiloxane, cyanopropylsiloxane, cation or anion exchanger siloxanes, liquid crystals, etc., may be selected according to the specific application need. Methods of bonding the selected stationary phase are well known to those skilled in the art of making open tubular fused-silica columns. The resulting stationary phase layer (20) may range in thickness from .1 to 5 μm. However, as noted below, a relatively thin layer (in the 0.1-1.0 range may be preferred.
The column is filled with packing material (25) comprising microparticulate silica. A selected stationary phase (not shown) is bonded to the micro-particulate silica prior to packing. The packing should preferably consist of substantially uniform particles having a diameter in the range of 1 to 200 μm. The method of packing a microbore fused-silica column is described in the inventor's U.S. Pat. No. 4,483,773.
In accordance with the present invention, it is not necessary that the stationary phase selected for the packing material be the same as the stationary phase (20) bonded to the column wall. Indeed, there may be distinct advantages to selecting a stationary phase for the wall that is different than the stationary phase of the packing material. It appears experimentally that, by selecting appropriate surface modification chemicals one can minimize surface adsorption sites and modify physicochemical interaction between solute molecules and the active sites on the column wall, adding one more parameter for control of chromatographic processes.
The scope of chemical modification of the surface of the inner wall may include, for example:
1) Modification of surface hydrophilic or hydrophobic activity. It appears that better column efficiency can be obtained if solute molecules are repelled from the column wall. It is hypothesized that this minimizes the wall transcolumn zone spreading of the solute peak. 2) Masking or creating surface adsorption sites. Surface adsorption sites, e.g., SiOH, may be masked by simple chemical deactivation of the column wall by known techniques. Selective surface adsorption sites can be created by depositing a stationary phase on the wall or by chemical modification of the wall in accordance with the present invention.
3) Modification with chemically bonded stationary phases to obtain additional selectivity, retention, resolution and sample capacity. Selective phases, e.g., liquid crystal, can also be used to modify the surface for isomeric and other separations.
Table 1 shows the chromatographic characteristics of relative retention between toluene and benzene and total plate count for anthracene for a four different columns. Three of the columns were prepared according to the present invention and compared to a untreated fused-silica column of the prior art. Relative retention, α , between toluene and benzene increases for the chemically modified columns (α≈1.52) compared to the untreated column (α≈1.41). This increase in relative retention suggests a significant intermolecular interaction between solute molecules and the stationary phase on the column wall. TABLE 1
EFFECT OF COLUMN WALL CHEMICAL NATURE (2 μm ODS. 50% ACN:50% H2O) α (toluene/benzene) N(plates/m) Pure fused silica 1.41 71K 0.25 μ m 5% phenylmethyl siloxane 1.52 39K
1.0 μm 5% phenylmethyl siloxane 1.53 23K
1.0 μ m Carbowax 20M 1.51 257K The plate count for the untreated column is 71,000 plates/m for anthracene. After a 5% phenylmethylsiloxane modification of the column wall, the plate count is reduced to 39,000 for a 0.25 μm film and to 23,000 for a 1.0 μm film.
Because there is only a slight difference in relative retention α of the two test components between the different films, the degradation of plate count with the thicker film may result from non-equilibrium distribution due to the thick film. These results suggest that a thinner film may be preferred.
With the Carbowax (polyethylene gycol) modification, a very significant improvement in column plate count is measured. This is also shown in Figure 2. A reduced plate height of 1.9 (257K plates/m, anthracene, k'= 36.5) was measured for the 2μm ODS, 35 cm x 0.32 mm I.D. column. This plate count is to date the highest number reported in LC using 2 μm particles. The reasons for this result are not fully understood. The improvement in column plate count may result from the non-polar nature of anthracene molecules which thus does not have significant soluability in the highly polar polyethylene gycol stationary phase. The anthracene is thus repelled from the column wall. This would minimize both wall adsorption effects (silanol and trace metal) and would also minimize transcolumn zone spreading of the solute band. The deactivation of adsorptive active sites such as silanol groups on the glass surface is also suspected as playing a role in column efficiency.
From the experimental data gathered to date, it appears that other chemical modifications of the walls of packed microbore columns may be used to significantly improve column performance. The number of possible stationary phases is quite large and the thickness of the layer varies over a significant range. The column configuration selected will largely depend on the intended application of the chromatograph. At present, the theoretical aspects are not well developed and can only provide limited guidance. Hopefully, these theoretical considerations will be explored and developed so that a systematic basis for wall modification can be applied.

Claims

Claims What is Claimed is:
1. A microbore column for use in liquid chromatography comprising, a packed tubular fused silica column having a diameter of less than approximately 600 μ m wherein the inner wall of said column has been deactivated and chemically bonded with a stationary phase.
2. The microbore column of claim 1 wherein said stationary phase is different than the stationary phase bonded to the packing material.
3. The microbore column of claim 2 wherein said stationary phase is chosen to mask surface adsorption sites on said inner wall.
4. The microbore column of claim 2 wherein said stationary phase is chosen to create surface adsorption sites on said inner wall.
5. The microbore column of claim 2 wherein said stationary phase is chosen to enhance hydrophilic activity on the surface of said inner wall.
6. The microbore column of claim 2 wherein said stationary phase is chosen to enhance hydrophobic activity on the surface of said inner wall.
7. The microbore column of claim 2 wherein said staionary phase is chosen to enhance selectivity, retention, resolution, or sample capacity.
8. The microbore column of claim 2 wherein said stationary phase is an organosiloxane.
9. The microbore column of claim 8 wherein said stationary phase is chosen from the group consisting of methylphenyliloxane, octylsiloxane, dimethylpolysiloxane, polyethylene glycol, dimethyldiphenylpolysiloxane, octadecylsiloxane, and cyanopropylsiloxane.
10. A process of making a microbore column for use in liquid chromatography comprising the steps of: selecting a fused-silica tubular column of a desired' length and with a diameter less than approximately 600 μ m , deactivating the inner wall of said column, chemically bonding a stationary phase to said inner wall, and uniformly packing said column.
11. The process of claim 9 wherein said stationary phase is different than the stationary phase bonded to the packing material.
12. The process of claim 10 wherein said stationary phase is an organosiloxane.
13. The process of claim 12 wherein said stationary phase is chosen from the group consisting of methylphenylsiloxane, octylsiloxane, dimethylpolysiloxane, polyethylene glycol, dimethyl-diphenylpolysiloxane, octadecylsiloxane, aminopropylsiloxane, and cyanopropylsiloxane.
EP19870907262 1987-04-15 1987-08-04 Fused-silica microbore packed chromatography column with chemically modified column wall. Withdrawn EP0309489A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US3827887A 1987-04-15 1987-04-15
US38278 1987-04-15

Publications (2)

Publication Number Publication Date
EP0309489A1 EP0309489A1 (en) 1989-04-05
EP0309489A4 true EP0309489A4 (en) 1989-09-11

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EP19870907262 Withdrawn EP0309489A4 (en) 1987-04-15 1987-08-04 Fused-silica microbore packed chromatography column with chemically modified column wall.

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JP (1) JPH01503256A (en)
WO (1) WO1988007886A1 (en)

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Publication number Priority date Publication date Assignee Title
US8778059B2 (en) 2007-12-03 2014-07-15 Schlumberger Technology Corporation Differential acceleration chromatography

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1421860A (en) * 1964-02-06 1965-12-17 Siemens Ag Gas chromatographic separation column
DE1498581A1 (en) * 1963-07-03 1969-01-23 Bayer Dr Ernst New method for the separation of liquids and solids by means of capillary liquid chromatography
US3878092A (en) * 1973-03-12 1975-04-15 Phillips Petroleum Co Chromatographic colums

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Publication number Priority date Publication date Assignee Title
US3666530A (en) * 1970-10-22 1972-05-30 Research Corp Novel silicious silicone bonded materials
US4029583A (en) * 1975-02-28 1977-06-14 Purdue Research Foundation Chromatographic supports and methods and apparatus for preparing the same
JPS5489691A (en) * 1977-12-24 1979-07-16 Nippon Bunko Kogyo Kk Open tube type capillary column for micro rapid liquid chromatography and production thereof
US4242227A (en) * 1979-07-31 1980-12-30 The Dow Chemical Company Chromatographic column packing having a bonded organosiloxane coating
US4376641A (en) * 1981-12-14 1983-03-15 The Dow Chemical Company Coated capillary chromatographic column
US4483773A (en) * 1982-10-04 1984-11-20 Varian Associates, Inc. Narrow bore micro-particulate column packing process and product
US4509964A (en) * 1984-01-04 1985-04-09 The Foxboro Company Fused silica capillary column
US4544485A (en) * 1984-08-31 1985-10-01 Purdue Research Foundation Chromatographic method and means

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1498581A1 (en) * 1963-07-03 1969-01-23 Bayer Dr Ernst New method for the separation of liquids and solids by means of capillary liquid chromatography
FR1421860A (en) * 1964-02-06 1965-12-17 Siemens Ag Gas chromatographic separation column
US3878092A (en) * 1973-03-12 1975-04-15 Phillips Petroleum Co Chromatographic colums

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO8807886A1 *

Also Published As

Publication number Publication date
WO1988007886A1 (en) 1988-10-20
JPH01503256A (en) 1989-11-02
EP0309489A1 (en) 1989-04-05

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