QCM-Based Electronic Nose for Near-Real-Time BTEX Detection

The detection of benzene, toluene, ethylbenzene, and xylene (BTEX) is critical for safety in the oil and gas industry due to their toxic and carcinogenic effects. This study presents a portable electronic nose (E-Nose) system based on quartz crystal microbalance (QCM) coated with polyvinyl acetate (PVAc) and tungsten oxide (WO3) for near-real-time detection of BTEX vapors in ambient conditions. The PVAc-coated QCM sensor achieved high sensitivity for benzene ( $5.14~\pm ~0.25$ Hz/ppm) and ethylbenzene ( $5.85~\pm ~0.31$ Hz/ppm), while the WO3-coated sensor demonstrated notable sensitivity to toluene ( $5.69~\pm ~0.22$ Hz/ppm). The sensitivity for xylene was in the range of $5.00~\pm ~0.31$ Hz/ppm for both sensors. The limits of detection (LOD) for PVAc- and WO3-coated sensors for BTEX were 1.69 and 1.26 ppm, respectively. The system was validated using gas chromatography-mass spectrometry (GC-MS), verifying the accurate detection of less than 4-ppm BTEX mixture with 2–3-min analysis times. Principal component analysis (PCA) combined with clustering algorithms, such as k-means and balanced iterative reducing and clustering using hierarchies (BIRCH), provided high classification accuracy, achieving silhouette scores of 0.53 and 0.51, respectively. This work demonstrates a novel approach to integrating QCM sensors with advanced data analytics for effective near-real-time BTEX monitoring in industrial environments.