Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Reexamination Certificate
1999-09-23
2001-11-27
Warden, Jill (Department: 1743)
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
C204S451000, C204S601000
Reexamination Certificate
active
06322682
ABSTRACT:
Hydrophobic polymeric materials are commonly utilized in laboratory equipment, medical supplies, membranes and have also recently found interest as column material in capillary electrophoresis (CE)(Liu et al., J. Microcol. Sep. 15 (1993) 245-). Unlike fused silica, these materials do not change surface characteristics depending on pH. Unfortunately it is difficult to fabricate hydrophilic materials with the same good mechanical properties as hydrophobic material.
Perfluorinated poly(ethylene-propylene) tubings (a flat 0.2×0.8 mm i.d. and a round 0.5 i.d.) have previously been evaluated as electrophoresis support by comparing IgG separation patterns (Izumi et al., J. High Resolut. 14 (1991) 351-). A higher voltage could be applied to the flat tubing owing to its smaller cross sectional area. The migration time in the analysis with the flat tubing was approximately 8 minutes shorter but without loss in resolution. The electrokinetic property of polymers of fluorinated hydrocarbons (PFC), polyethylene (PE) and poly(vinyl chloride) (PVC)) (Schützner et al., Anal. Chem. 64 (1992) 1991-) has also been investigated and very similar surface characteristics were found. In contrast to fused silica, the zeta potentials, and thereby also the electro osmotic flow (EOF), obtained using these polymeric materials are influenced only to a small extent by addition of organic solvents, like ethanol, acetonitril or dimethyl sulphoxide, in the electrolyte. Polymeric materials have not been studied in more detail to date, maybe due to the difficulty to make and/or buy uniform hollow fibers with small i.d. (50-60 &mgr;m) as well as the disadvantage of low UV transparency of these materials.
Polypropylene hollow fibers have recently become an interesting alternative to fused silica capillaries for capillary electrophoresis due to their transparency in the visible and near UV region (Nielen et al., J. High Resolut. 16 (1993) 62-). This property also makes polypropylene hollow fibres well-fitted for fluorescence detection systems (Nielen et al., J. Chromatog. 608 (1992) 85-). A potential problem of neat polypropylene or other hydrophobic polymeric materials, such as polyvinyl chloride (PVC), PFC, PE etc, is their hydrophobicity that results in low surface wetability by aqueous solutions. This can lead to severe hydrophobic surface-analyte interactions making it impossible to analyze compounds like proteins on untreated hollow fibers made of this type of material. A hydrophilic surface coating should therefore be of advantage in order to minimize adsorption. Poppe et al (Busch et al., J. Chromatog. 695 (1995) 287-) recently reported on the use of crosslinked hydroxypropyl cellulose (HPCc) to modify the inner surface of a polypropylene hollow fiber. A separation of basic proteins on HPCc treated fused silica capillaries and polypropylene hollow fibers, respectively, resulted in comparable relative standard deviations (RSD) of the migration times and theoretical plate numbers. Covalent bonding of polyacrylamide to polypropylene hollow fibers has also been reported (Liu et al., J. Microbiol. Sep. 15 (1993) 245-; and Liu et al,. J. Microbiol. Sep. 6 (1994) 581-). It has been shown in micellar electrokinetic capillary chromatography (MECC) that a surfactant like sodium dodecyl sulphate (SDS) adsorbed to a polypropylene surface resulted in a high and pH independent electro osmotic flow (Fridström et al., Chromatographia 41 (1995) 295-).
The ideal surface for protein analysis in capillary electrophoresis is a surface which is stable over a wide pH range and which in particular have a high hydrophilicity minimizing adsorption. Dextran polymers have in general been found to possess these properties. Dextran is a hydrophilic polymer known to have low protein adsorption, and is capable of being derivatized with hydrophobic functional groups. It has been shown that membranes coated by dextran resulted in decreased protein adsorption (Henis et al, U.S. Pat. No. 4,794,002). Hjertén et al (Electrophoresis 14 (1993) 390-) found that crosslinked allyldextran on a fused silica surface resisted washing with sodium dodecyl sulphate in alkaline solutions. Mechref et al (Electrophoresis 14 (1993) 390-) have reported high pH-stability of dextran-polyethylene glycol crosslinked surfaces on fused silica. If the dextran has non-polar substituents that can be attracted by physical adsorption to the propylene surface it should be possible to utilize this physical attraction to give a stable surface without the requirement to chemically bind the dextran to the wall or by internal immobilization.
The use of various hydrocarbyl (alkyl, alkenyl and/or phenyl) substituted polyhydroxy polymers for preparing and/or attaching gel layers or hydrophilic coats to plastic surfaces has also been described (Allmér WO 9529203; Henis et al (U.S. Pat. No. 4,794,002 and US 5,139,881); Varady (U.S. Pat. No. 5,030,352); Ericsson et al (SE 9600612-7), and Söderberg U.S. Pat. No. 4,094,832).
OBJECTIONS OF THE INVENTION
The primary objective of the invention is to provide new capillary electrophoresis supports combining the mechanical and chemical stability of fused silica capillaries with low electro osmotic flow, weak or no surface interaction with electrophoresed substances, transparency, etc.
REFERENCES:
patent: 3728145 (1973-04-01), Hjerten
patent: 4690749 (1987-09-01), Van Alstine et al.
patent: 5015350 (1991-05-01), Wikterowicz
Arvidsson Lars-Erik
Ekstrom Bjorn
Fulbright & Jaworski L.L.P.
Gyros AB
Starsiak Jr. John S.
Warden Jill
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