*Dhananjay I. Patel¹, Tuhin Roychowdhury¹, Dhruv Shah¹, Collin Jacobsen¹, Jason S. Herrington², Jason Hoisington² Colton Myers², Bryan G. Salazarc³, Amy V. Walker³, David S. Bell², Matthew R. Linford^1
1Brigham Young University, Provo, UT; ²Restek Corporation, Bellefonte, PA; ³University of Texas at Dallas, Richardson, TX
We describe the fabrication of solid phase microextraction (SPME) fibers based on porous, sputtered silicon coatings terminated with 6-phenylhexyl silane ultrathin films for the analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental samples. PAHs are carcinogenic pollutants often found in the air, water, and in food products. Our fabrication process involves sputtering silicon onto fused silica fibers followed by vapor phase deposition of 6-phenylhexyl silane. The silicon coatings were sputtered under various conditions, e.g., time and throw distances. Six different morphologies were obtained at three different thicknesses of sputtered silicon (0.5, 1.8, and 2.8 µm), and at two different throw distances (4 and 20 cm). The thickness of the silane coating was similar on each fiber (ca. 2 nm). These coatings were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), time-of flight secondary ion mass spectrometry (ToF-SIMS), spectroscopic ellipsometry (SE), and water contact angle goniometry. SPME fibers were investigated for the analysis of PAHs using gas chromatography-mass spectrometry (GC-MS). The best fiber created had a 2.8 µm thick sputtered silicon layer that was deposited at a throw distance of 20 cm. It shows competitive extraction efficiency for the low molecular weight (MW) PAHs in water when compared with a commercial 7 µm PDMS fiber. However, this fiber has ca. 3 times greater extraction efficiency for higher MW PAHs. Additionally, this fiber outperformed the commercial 7 µm PDMS fiber by showing better linearity (0.02-1.33 parts per billion), repeatability (5-24%), and detection limits (7-64 parts per trillion).