Department of Chemistry and Biochemistry, Brigham Young Univer...

We describe a new process for preparing porous solid phase microextraction SPME coatings by the sputtering of silicon onto silica fibers The microstructure of these coatings is a function of the substrate geometry and mean free path of the silicon atoms and the coating thickness is controlled by the sputtering time Sputtered silicon structures on silica fibers were treated with piranha solution a mixture of concd H2SO4 and 30 H2O2 to increase the concentration of silanol groups on their surfaces and the nanostructures were silanized with octadecyldimethylmethoxysilane in the gas phase The attachment of this hydrophobic ligand was confirmed by X-ray photoelectron spectroscopy and contact angle goniometry on model planar silicon substrates Sputtered silicon coatings adhered strongly to their surfaces as they were able to pass the Scotch tape adhesion test The extraction time and temperature for headspace extraction of mixtures of alkanes and alcohols on the sputtered fibers were optimized 5 min and 40 C and the extraction performances of SPME fibers with 1 0 or 2 0 m of sputtered silicon were compared to those from a commercial 7 m poly dimethylsiloxane PDMS fiber For mixtures of alcohols aldehydes amines and esters the 2 0 m sputtered silicon fiber yielded signals that were 3-9 3-5 2 5-4 5 and 1 5-2 times higher respectively than those of the commercial fiber For the heavier alkanes undecane-hexadecane the 2 0 m sputtered fiber yielded signals that were approximately 1 0-1 5 times higher than the commercial fiber The sputtered fibers extracted low molecular weight analytes that were not detectable with the commercial fiber The selectivity of the sputtered fibers appears to favor analytes that have both a hydrophobic component and hydrogen-bonding capabilities No detectable carryover between runs was noted for the sputtered fibers The repeatability RSD for a fiber n 3 was less than 10 for all analytes tested and the between-fiber reproducibility n 3 was 0-15 generally 5-10 for all analytes tested The repeatabilities of our sputtered fibers and the commercial 7 m PDMS fiber are essentially the same Fibers could be used for at least 300 extractions without loss of performance More than 50 compounds were identified in a gas chromatography-mass spectrometry headspace analysis of a real world botanical sample with the 2 0 m fiber

Department of Chemistry and Biochemistry, Brigham Young University , Provo, Utah 84602, United States.

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Porous, High Capacity Coatings for Solid Phase Microextraction by Sputtering.