A stainless steel fiber was coated with a gate-opening controlled metal-organic framework ZIF-7 via a sol-gel method and applied to the solid-phase microextraction of aldehydes (hexanal, heptanal, octanal, nonanal, decanal) from exhaled breath by lung cancer patients. The effects of temperature and time on the sorption and desorption were optimized. Under optimum condition, the modified fiber displays enrichment factors (typically ranging from 300 to 10,000), low limits of detection (0.61-0.84 μg L-1), and wide linear ranges of hexanal, heptanal (5-500 μg L-1) and octanal, nonanal, decanal (10-1000 μg L-1). The high extraction capability for aldehydes is thought to result from (a) the combined effects of the large surface area and the unique porous structure of the ZIF-7, (b) the hydrophobicity and gate-opening effect of the sorbent, (c) the high selectivity of the window, and (d) the presence of unsaturated metal-coordination sites. The coated fiber is thermally stable and can be re-used >150 times. The relative standard deviation (RSD) for six replicate extractions using a single fiber ranged from 1.4-15.3% for intra-day and 2.4-16.1% for inter-day. The fiber-to-fiber reproducibility for three fibers prepared in parallel was in the range of 2.4-12.6% (RSD). The method was applied to the extraction of aldehydes from real samples and to the quantitation by gas chromatography. Recoveries from spiked samples ranged from 84 to 113%. Graphical abstract A metal-organic framework ZIF-7 coated stainless steel fiber was prepared via sol-gel method. The self-made fiber was applied in the solid phase microextraction of aldehydes from exhaled breath of lung cancer patients.
Keywords: Benzimidazole; Breath analysis; Flame ionic detector; Gas chromatography; Sol-gel; Stainless steel wire; Tedlar bag; Volatile organic compounds.