Research Article Surface Plasmon Resonance Sensor to Detect n-Hexane in Palm Kernel Oil Using Polypyrrole Nanoparticles Reduced Graphene Oxide Layer Amir Reza Sadrolhosseini , 1 Mina Habibiasr, 2 Hassan Soleimani, 3 Mohd Nizar Hamidon , 1 Yap Wing Fen, 1,4 and H. N. Lim 5 1 Functional Device Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400UPM, Serdang, Selangor, Malaysia 2 Department of Process and Food Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400UPM, Serdang, Selangor, Malaysia 3 Department of Fundamental and Applied Science, Universiti Teknologi PETRONAS, 3175 Seri Iskandar, Malaysia 4 Department of Physics, Faculty of Science, University Putra Malaysia, 43400UPM Serdang, Selangor, Malaysia 5 Department of Chemistry, Faculty of Science, University Putra Malaysia, 43400UPM Serdang, Selangor, Malaysia Correspondence should be addressed to Amir Reza Sadrolhosseini; amir17984818@gmail.com and Mohd Nizar Hamidon; mnh@upm.edu.my Received 10 March 2020; Revised 14 September 2020; Accepted 7 October 2020; Published 4 January 2021 Academic Editor: Aitor Urrutia Copyright © 2021 Amir Reza Sadrolhosseini et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Palm kernel oil was extracted using n-hexane. Rotary evaporator and oven were used to remove n-hexane from the oil. Measurement of n-hexane in low concentration is significant and interest subject. In this study, the concentration of n-hexane was measured using the surface plasmon resonance technique. In order to improve the sensitivity of surface plasmon resonance sensor, the polypyrrole nanoparticles decorated reduced graphene oxide (sensing layer) was prepared using the electrodeposition technique on the surface of gold film. Different concentration of n-hexane in isooctane and the palm kernel oil before and after purification was tested using sensing layer. The sensor limit was about 1 ppm. The results were matched with the gas chromatography results. The thickness and roughness of sensing layer were increased after the interaction with n-hexane which was obtained from atomic force microscopy. 1. Introduction Palm kernel oil is rich in saturated fatty acids and a small amount of unsaturated fatty acids. Palm kernel oil is a white to yellowish oil which is solid at normal temperature and is considered a secondary product of palm fruit [1]. Palm ker- nel oil contains approximately 80% saturated fatty acid com- prised of C12 or lauric acid (48.7%), C14 or myristic acid (15.6%), and C16 or palmitic acid (7.5%). Unsaturated fatty acids are included C18:1 or oleic acid (14.8%) and C18:2 or linoleic acid (2.6%) [2]. Solvent extraction in organic solution is a popular method for palm kernel oil extraction [3]. Cur- rently, n-hexane is the preferred solvent throughout the world. n-Hexane has been categorized as a hazardous air pollutant (HAP) by the US Environmental Protection Agency, and it is included in the list of toxic chemicals [4]. According to PFA Act 1954, the maximum permissible limit for n-hexane in oil and the meal are about 5 ppm and 10 ppm, respectively [5]. Therefore, n-hexane must be removed totally from palm kernel oil after extraction of oil from the kernel. Typically, rotary evaporator and oven are used to eliminate the n-hexane from palm kernel oil. The analytical methods such as Fourier transform infrared spectroscopy (FT-IR) [6] and gas chromatography (GC) [7] are used to measure the concentration of n-hexane. The mentioned methods are complicated, and they depend on chemical Hindawi Journal of Sensors Volume 2021, Article ID 8813801, 13 pages https://doi.org/10.1155/2021/8813801