Liquid purification or separation – Processes – Chromatography
Reexamination Certificate
1999-08-02
2001-02-20
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
Processes
Chromatography
C210S198200, C210S088000, C095S082000, C095S088000, C096S101000
Reexamination Certificate
active
06190559
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention pertains to a novel method of packing capillary columns. More particularly, the invention pertains to a method of packing capillary columns by drawing a slurry of packing material into a capillary column through capillary action, and then removing solvent from the slurry through one end of the column.
There are a variety of methods currently in use for packing capillary columns, such as those columns used in the fields of chromatography and electrospray ionization mass spectrometry (ESI-MS). The most popular methods in current use are the so-called “slurry packing” methods.
U.S. Pat. No. 5,679,255 discloses a method whereby a retaining material, such as a ceramic frit which will allow solvent, but not packing material, to pass is placed in one end of the column. A slurry of polymeric packing material in an organic solvent, such as THF, is then pumped through the column, from the end opposite that having the retaining frit. The packing material thereby accumulates in the column, while the liquid portion of the slurry passes out through the frit. This method has certain disadvantages, however. The capillary tubing used must be capable of withstanding the pressure generated by the pumping of the slurry into the tube, and necessary equipment, such as a pump and solvent recovery system must be provided.
High packing pressure may also cause deterioration of or damage to the packing material.
U.S. Pat. No. 4,483,773 discloses a method wherein an end restriction is first placed in a column, to permit the flow of solvent, but restrict the passage of particles out of the end of the column. A slurry is then caused to flow into the column, under pressure. A two-step pressure sequence is then used to first fill up the column and form a bed of particles and then to uniformly compress the bed.
This method is less than completely satisfactory, because special equipment is required to practice it.
There is therefore a need for a simple, direct method for packing capillary columns, which does not rely on special equipment for pumping or pressurizing slurries into the columns.
SUMMARY OF THE INVENTION
It has now been discovered that a slurry of packing material can be drawn up into a capillary column through capillary action and that when the solvent in the slurry is evaporated out of the slurry through the same end of the column through which the slurry entered, the packing that is originally suspended in the slurry migrates towards the end of the column to become closely packed.
In accordance with the invention, there is therefore provided a method for packing a capillary column which comprises forming a slurry of the packing material to be packed into the column, placing the slurry in a vessel, inserting one end of a capillary column into said slurry in said vessel or reservoir, drawing slurry into said column by capillary action and removing the solvent from the slurry that has been drawn into the column through the same end through which it entered the column. Preferably, the solvent is removed only from the end through which it entered the column, and it is particularly preferable that the solvent be removed through only the same end through which it entered the column, by evaporation.
Finally, after the solvent has been removed from the slurry that has been drawn into the column, leaving only the packing material that was in the slurry, a portion of the packing at the end of the column is optionally sintered.
REFERENCES:
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patent: 4793920 (1988-12-01), Cortes et al.
patent: 4966696 (1990-10-01), Allington et al.
patent: 5453163 (1995-09-01), Yan
patent: 5679255 (1997-10-01), Cortes et al.
Tsuda et al., Analytical Chemistry, vol. 50, No. 2, (Feb. 1978) pp. 271-275 “Packed Microcapillary Columns in High Performance Liquid Chromatography”.
Shelly et al., Analytical Chemistry, vol. 56, (1984) pp. 2990-2992 “Aids for Analytical Chemists: Dead-Volume Free Termination for Packed Columns in Microcapillary Liquid Chromatography”.
Crescentini et al., Analytical Chemistry, vol. 60, (1988) pp. 1659-1662 “Preparation and Evaluation of Dry-Packed Capillary Columns for High-Performance Liquid Chromatography”.
Kennedy et al., Analytical Chemistry, vol. 61, (1989) pp. 1128-1135.
Cappiello et al., Chromatographia, vol. 32, (1991) pp. 389-391 “New Materials and Packing Techniques for Micro-HPLC Packed Capillary Columns”.
Fermier, et al., J. Microcolumn Separations, vol. 10, (1998) pp. 439-447 “Capillary Electrochromatography in Columns Packed by Centripetal Forces”.
Li, et al., Rev. Sci. Instruments, vol. 62, (1991) pp. 2630-2633 “Polystyrene latex particles as size calibration for the atomic force microscope”.
Dushkin et al., Langmuir, vol. 9, (1993) pp. 3695-3701 “Colored Multilayers from Transparent Submicrometer Spheres”.
Norris McLaughlin & Marcus P.A.
Therkorn Ernest G.
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