PVDF/M5AH@UiO-66-NH₂ composite membrane: Efficient separation of breath acetone/isoprene and highly sensitive...

Cavity ringdown spectroscopy (CRDS) is a sensitive laser absorption technique that can detect volatile organic compounds (VOCs) in human breath. Notably, CRDS exhibits a distinct absorbance for exhaled isoprene, a potential biomarker for lung cancer, at a wavelength of 226.56 nm. However, the presence of acetone in breath samples interferes with the accurate measurements of isoprene by CRDS. To address this issue, we developed a novel PVDF/M5AH@UiO-66-NH₂ composite membrane for the ultra-trace separation of isoprene and acetone at ppbv levels (volume concentration of 10^-9). As verified by PTR-TOF-MS, the optimal modified membrane, PVDF/M5AH@UiO-66-NH₂0.5, effectively reduced the acetone concentration by approximately 89.2 % ± 2.7 %, while minimally affecting the isoprene concentration (8.9 % ± 4.0 %). Analysis of breath samples from 76 lung cancer patients and 92 healthy controls, using both PTR-TOF-MS and CRDS techniques, revealed that the exhaled isoprene levels in healthy controls (238.7 ± 106.2 ppbv) were higher than those in patients (169.0 ± 52.6 ppbv). After membrane separation, CRDS showed a significant decrease in isoprene concentration among lung cancer patients, from 294.8 ± 65.4 ppbv to 191.1 ± 56.0 ppbv, thereby improving diagnostic accuracy. Moreover, the receiver operating characteristic (ROC) curve analysis demonstrates the enhanced diagnostic potential of exhaled isoprene after membrane separation, highlighting its potential in biomarker validation, sensitive and accurate clinical diagnosis, and long-term monitoring.