Sputtered silicon solid phase microextraction fibers with a polydimethylsiloxane stationary phase with negligible carry-over and phase bleed

Tuhin Roychowdhury; Dhananjay I Patel; Dhruv Shah; Anubhav Diwan; Massoud Kaykhaii; Jason S Herrington; David S Bell; Matthew R Linford

doi:10.1016/j.chroma.2020.461065

Sputtered silicon solid phase microextraction fibers with a polydimethylsiloxane stationary phase with negligible carry-over and phase bleed

J Chromatogr A. 2020 Jul 19:1623:461065. doi: 10.1016/j.chroma.2020.461065. Epub 2020 Apr 12.

Authors

Tuhin Roychowdhury¹, Dhananjay I Patel¹, Dhruv Shah¹, Anubhav Diwan², Massoud Kaykhaii³, Jason S Herrington⁴, David S Bell⁴, Matthew R Linford⁵

Affiliations

¹ Department of Chemistry & Biochemistry, Brigham Young University, Provo, UT 84602, USA.
² Moxtek, Inc., 452 W 1260 N, Orem, UT 84057, USA.
³ Department of Chemistry, Faculty of Sciences, University of Sistan and Baluchestan, Zahedan, Iran.
⁴ Restek Corporation, 110 Benner Circle, Bellefonte, PA 16823, USA.
⁵ Department of Chemistry & Biochemistry, Brigham Young University, Provo, UT 84602, USA. Electronic address: mrlinford@chem.byu.edu.

PMID: 32448558
DOI: 10.1016/j.chroma.2020.461065

Abstract

We report the preparation of high performance, sputtered, polydimethylsiloxane (PDMS)-coated solid phase microextraction (SPME) fibers that show negligible carry-over and phase bleed. This process involves sputtering silicon onto silica fibers and functionalizing the resulting porous nanostructures with ultrathin films of vapor-deposited PDMS. Different thicknesses of silicon (0.25, 0.8, and 1.8 µm) and PDMS (8, 16, and 36 nm) were produced and their extraction efficiencies evaluated. The deposition of PDMS was confirmed by time-of-fight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and contact angle goniometry on model, planar silicon substrates. These fibers were investigated using direct immersion SPME coupled with gas chromatography-mass spectrometry (GC-MS) analysis of a series of polycyclic aromatic hydrocarbons (PAHs), which are carcinogenic pollutants. The 1.8 µm thick silicon coating with 16 nm of PDMS (Si (1.8 µm)/PDMS (16 nm)) produced the best response among the combinations tested. Conditions for the extraction of PAHs with this fiber were optimized and its extraction performance was compared to that of a commercial 7 μm PDMS fiber. The linearity (1-110 µgL^-1), repeatability (RSD%, n = 3) (17% ave.), and minimum detection limits (0.6-1.5 µgL^-1) of the sputtered fibers were determined and found to be superior to the commercial 7 µm PDMS fiber in many respects. Carry-over and phase bleed from commercial PDMS-based SPME fibers are two of their major drawbacks, which decrease their lifetimes and usefulness. Minimal carry-over and phase bleed were observed for our sputtered PDMS-coated fibers. In particular, our fiber only shows 12% of the phase bleed of the comparable commercial fiber. In addition, it shows no carry-over for analytes with retention times greater than pyrene, and only 5% of the carry-over of the other analytes. Our fibers could be used for at least 300 injections without any significant loss of performance.

Keywords: Carry-over; Linearity; Minimum detection limit; PDMS; Phase bleed; Polycyclic aromatic hydrocarbons (PAHs); Repeatability; SPME; Silicon.

MeSH terms

Dimethylpolysiloxanes / chemistry*
Gas Chromatography-Mass Spectrometry
Limit of Detection
Photoelectron Spectroscopy
Polycyclic Aromatic Hydrocarbons / analysis
Silicon / chemistry*
Solid Phase Microextraction / methods*
Temperature
Time Factors
Water / chemistry
Water Pollutants, Chemical / analysis

Substances

Dimethylpolysiloxanes
Polycyclic Aromatic Hydrocarbons
Water Pollutants, Chemical
Water
Silicon