title: Sol-gel approach to in situ creation of high pH-resistant surface-bonded organic-inorganic hybrid zirconia coating for capillary microextraction (in-tube SPME).
abstract: A novel zirconia-based hybrid organic-inorganic sol-gel coating was developed for capillary microextraction (CME) (in-tube SPME). High degree of chemical inertness inherent in zirconia makes it very difficult to covalently bind a suitable organic ligand to its surface. In the present work, this problem was addressed from a sol-gel chemistry point of view. Principles of sol-gel chemistry were employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network in the course of its evolution from a highly reactive alkoxide precursor undergoing controlled hydrolytic polycondensation reactions. A fused silica capillary was filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary for a predetermined period of time (typically 15-30 min). In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer got chemically anchored to the silanol groups on the capillary inner walls via condensation reaction. At the end of this in-capillary residence time, the unbonded part of the sol solution was expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia-PDMDPS coating on the inner walls. Polycyclic aromatic hydrocarbons, ketones, and aldehydes were efficiently extracted and preconcentrated from dilute aqueous samples using sol-gel zirconia-PDMDPS coated capillaries followed by thermal desorption and GC analysis of the extracted solutes. The newly developed sol-gel hybrid zirconia coatings demonstrated excellent pH stability, and retained the extraction characteristics intact even after continuous rinsing with a 0.1 M NaOH solution for 24 h. To our knowledge, this is the first report on the use of a sol-gel zirconia-based hybrid organic-inorganic coating as an extraction medium in solid phase microextraction (SPME).
authors.affiliation: Department of Chemistry, University of South Florida, Tampa, FL 33620-5250, USA.
authors.forename: Khalid
authors.initials: K
authors.lastname: Alhooshani
authors.forename: Tae-Young
authors.initials: TY
authors.lastname: Kim
authors.forename: Abuzar
authors.initials: A
authors.lastname: Kabir
authors.forename: Abdul
authors.initials: A
authors.lastname: Malik
mesh_terms: D002849:Chromatography, Gas / Q000379:methods*; D005782:Gels; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D005782:Gels; D015040:Zirconium; C028541:zirconium oxide