Metal-organic framework-coated stainless steel fiber for solid-phase microextraction of polychlorinated biphenyls

For solid phase microextraction (SPME), effective immobilization of sorbent on a stainless steel fiber surface is very essential. But, it still remains challenging because the chemical inertness of stainless steel fiber. In this work, chemical bonding method was introduced to fabricate a series of metal-organic frameworks (MOFs)-coated stainless steel fibers, and some representative MOFs (ZIF-90 (Zn), MOF-199 (Cu), MIL-101 (Cr), MOF-5 (Zn))-coated stainless steel fibers were successfully synthesized. Such strategy can noticeably increase the mechanical and chemical stability, and prolong the service lifetime due to it combine the advantages of stainless steel fiber and chemical bonding method. The stability of MOF-ZIF-90 (Zn)-coated stainless steel fibers which were preparated by different methods (chemical bonding method, adhesive method and deposition method) were studied, and results showed the chemical bonding method proved the best stability. Based on the ZIF-90 (Zn)-coated fiber, the SPME-GC-MS method was developed for detecting traces of polychlorinated biphenyls (PCBs) and satisfactory results were obtained. The linear ranges were 0.01-600 ng L^-1 and the coefficient of determination was higher than 0.993. The limits of detection for the PCBs were 0.0013-0.053 ng L^-1. The recoveries for the spiked PCBs in the Minjiang water, soil and vegetable oil samples were in the range of 85.9-105.8%. The extraction capacity of the ZIF-90 (Zn)-coated stainless steel fiber prepared by chemical bonding method did not show measurable change under different temperatures or organic solvents for up to 5 days.