Tube structure with sol-gel zirconia coating

Abstract

The subject invention concerns zirconia-based hybrid organic-inorganic sol-gel coating for optional use as a stationary phase in capillary microextraction (CME), gas chromatographic (GC), high performance liquid chromatography (HPLC), capillary electrophoresis (CE), capillary electrochromatography (CEC) and related analytical techniques. Sol-gel chemistry is employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network. In one embodiment, a fused silica capillary is filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary. In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer becomes chemically bonded to the silanol groups on the inner capillary walls. The unbonded part of the sol solution is expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia —PDMDPS coating on the inner walls of the capillary. Polycyclic aromatic hydrocarbons, ketones, and aldehydes are efficiently extracted and preconcentrated from dilute aqueous samples followed by GC separation of the extracted analytes.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation of U.S. application Ser. No. 10 / 704,766, filed Nov. 10, 2003, which claims the benefit of U.S. Provisional Application Ser. No. 60 / 319,680, filed Nov. 8, 2002.BACKGROUND OF THE INVENTION [0002] Solid phase microextraction (SPME) was developed in 1989 by Belardi and Pawliszyn to facilitate rapid sample preparation both for the laboratory and field analysis. It provided a simple and efficient solvent-free method for extraction and preconcentration of analytes from various sample matrices. In SPME, a sorptive stationary phase coating, (either on the outer surface of a fused silica fiber or on the inner surface of a fused silica capillary) actually serves as the extraction medium in which the analytes get preferentially sorbed and preconcentrated. Polymeric surface coatings are predominantly used in conventional fiber-based SPME as well as in the newly materialized in-tube SPME, also referred to as capillar...

AI Technical Summary

Benefits of technology

[0008] The present invention relates to zirconia-based stationary phases for chromatographic separations and sample preconcentrations. Zirconia has many unique properties that make it attractive as a chromatographic support material. Zirconia's most notable properties are: it's excellent chemical and pH stability, inertness, and unique surface chemistry. In the present method, sol-gel chemistry is used to exploit these properties by in situ preparation of zirconia-based stationary phases within separation columns and extraction tubes. The utility of the created columns and extraction tubes are demonstrated by experimental results on gas chromatographic separations obtained on sol-gel zirconia coated capillary columns and capillary microextraction results obtained on sol-gel zirconia-coated capillaries.

Problems solved by technology

Sol-gel organic-inorganic hybrid materials provide desirable properties that are difficult to achieve using either purely organic or purely inorganic materials.

The main drawback of silica-based stationary phases is the narrow range of pH stability.

Under extreme pH conditions silica-based stationary phases become chemically unstable, and their stationary phase properties are compromised.

Under highly acidic pH conditions, silica-based bonded stationary phases become hydrolytically unstable.

Images