Development of solid-phase microextraction fibers based on multi-walled carbon nanotubes for pre-concentration and analysis of alkanes in human breath

In this work, a laboratory preparation method based on sol-gel technology was proposed to develop a new kind of SPME (solid phase microextraction) fibers. Multi-walled carbon nanotubes (MWCNT) were selected as sol-gel active organic component. Stainless steel wires were used as the substrate of the fibers. Instead of traditional modification methods, microwave induced plasma was used to modify the stainless steel wire surface, resulting in a significant improvement in chemical adhesion of the fiber substrate and coating. The MWCNT coating exhibited several good properties. Acceptable fiber-to-fiber reproducibility (RSD ≤ 13%) and repeatability (RSD < 7%) were obtained. End-tidal breath of 10 normal humans were collected by Bio-VOC® sampler and assayed by the optimized SPME-GC-MS method. The calibration curves were all linear (R2 ≥ 0.994) in the range from 0.03 to 403.3 ppbv for five alkanes. Detection limits (down to 0.001 ppbv) were about one order of magnitude better than those of commercial PDMS fibers. The recovery of the spiked alkanes in real breath sample at 1 ppbv ranged from 89.71 to 101.08% and the relative standard deviations were less than 8%. These results demonstrated the feasibility and practicality of the proposed preparation procedure. Applications of the in-house fabricated fibers for human breath analysis were successfully verified.