Comparing the Selectivity of Solid Phase Microextraction Fibers to Detect Volatile Organic Compounds

Volatile organic compounds (VOCs) have been shown to be biomarkers of disease and are typically identified by gas chromatography-mass spectrometry (GC-MS) or gas sensor arrays (electronic nose, e-nose). GC-MS has the advantages of VOC structure elucidation, while the e-nose is easy to use and offers point of care applications. Current e-nose designs utilize a sensor array to adsorb a diverse set of VOCs, some of which are biomarkers. Because the sensor elements are not tuned for biomarkers, these devices must rely on machine learning to identify disease. Therefore, tuning the selectivity of the sensing layers to detect specific biomarkers may increase diagnostic accuracy. Solid phase microextraction (SPME) coupled to GC-MS may be a rapid and facile process to evaluate different sensing layers. To demonstrate this concept, SPME fibers of different compositions were fabricated (custom fibers) and compared to commercially available polyacrylate (PAA) fibers. Coatings were characterized by Fourier Transform Infrared spectroscopy and scanning electron microscopy. Custom, PAA and uncoated (negative controls) SPME fibers were utilized to extract a standard VOC mixture which was analyzed by GC-MS. PAA and custom fibers significantly outperformed the negative control, but PAA fibers were more sensitive. However, the custom fiber was nearly twice as selective to some VOCs and the PAA fiber was nearly twice as selective toward other VOCs. The results show that SPME GC-MS is an efficient method for testing/comparing the selectivity of sensing layers toward multiple VOCs in a single analytical run.