Development of a portable, low-cost QCM sensor-based device for detecting α-pinene in Indian cardamom

One of the key quality indicators for Indian cardamom is alpha-pinene. To detect alpha-pinene, linoleic acid, a constituent fatty acid present in rice bran oil, was found responsible for the physisorption of alpha-pinene through Van der Waals (vdW) interaction. For the analysis and study of the sensing behaviour of alpha-pinene, a portable gas measuring device incorporating the rice bran oil coated quartz crystal microbalance sensor (RB-QCM) is developed for real -time detection. The sensor offers a good sensitivity (0.367 Hz/ppm) and a rapid response/recovery time (6 s/11 s). The physical adsorption affinity of alpha-pinene is calculated using the Langmuir, Freundlich, and Langmuir-Freundlich isotherm models. For estimating alpha-pinene in cardamom samples, the sensor demonstrated a coefficient of 0.98, with the peak area (%) determined by gas chromatography-mass spectrometry (GC-MS). SEM, FTIR, and AFM are used to analyse the structure and morphology of the sensor coating. According to this study, the rice bran oil-coated QCM sensor is a promising method for detecting alpha-pinene.