Efficient Citronellal Detection in Essential Oils: A Molecular Imprinted Polymer-Based Quartz Crystal Microbalance Sensor Approach

Citronellal, a significant aldehyde monoterpene found in various kinds of Cymbopogon species (lemongrass), has multiple applications in aromatherapy tools, personal care items, nontoxic biopesticide, and also as a natural insect repellant. Citronellal is the main ingredient that has the highest concentration in citronella essential oil (CEO). In this study, a quartz crystal microbalance (QCM) sensor coated with highly selective molecularly imprinted polymer has been described for the detection of citronellal in different commercially available CEOs. The surface of the quartz crystal was modified by in situ casting of engineered citronellal imprinted copolymer of acrylonitrile (ACN) and acrylic acid (AA). Among all possible combinations of acrylates, this composition showed the best performance. The molecular imprinting (MIP) material characterization and surface morphology were confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM). The linear operating range of the proposed sensor was observed to be 10–600 ppm. The fabricated sensor yielded a high sensitivity of 0.100 Hz/ppm with a high correlation factor (CF) of 0.999. Furthermore, the fabricated sensor provided a high repeatability of 92.47% and a reproducibility of 90.99%. A significant correlation of the sensor performance had been achieved concerning gas chromatographic analysis of commercially available CEO samples.