Development of molecularly imprinted polymer (MIP) based sensor array for the detection of mango volatiles

Abstract

This thesis discussed the development of molecularly imprinted polymers (MIP) based sensor array for the detection of Harumanis mango volatiles. Conventionally, the detection of mangoes maturity are based on human smell, texture and harvesting time. Unfortunately, these methods are not a quantifiable parameter to gauge the maturity. Maturity and ripeness were detected by the emission of volatiles as a marker using analytical equipment such as solid phase micro-extraction (SPME), crude extraction and liquid-liquid extraction. The analytical equipment is not practical because it cannot be operated outside the laboratory area. From gas chromatography mass spectrophotometer (GCMS) studies, Harumanis mangoes were found to emit certain volatiles during each different stage of maturity for example monoterpenes hydrocarbon which are known as marker component for mango maturity. Utilizing this chemical marker form GCMS data, the MIP sensor was developed on Interdigitated Electrode (IDE) and Quartz Crystal Microbalance (QCM) platforms where the sensors performances were tested. Computational simulation was implemented to simulate the MIP properties through molecular modeling and thermodynamic calculations using HyperChem 8.0 software. The molecular modeling with the use of semi-empirical method of AM1 (Austin Method 1) was used to find the optimum ratio of complex template and functional monomer methacrylic acid (MAA). Based on the binding energy (ΔE) obtained from the modelling, ratio 5 of MAA over template α-pinene and γ-terpinene and ratio 3 of MAA over terpinolene have good binding capabilities during polymeric synthesis. The sensors responses on QCM and IDE were found to have consistent selectivity regardless of the platform used which is quartz crystal or PET (Polyethylene terepthlate). The MIP sensor was also exposed real time to Harumanis mango where the response pattern indicated that the sensor responded towards its target analyte and able to clarify fruits at various maturity phases. In this research, MIP sensor was successfully developed and the selectivity response was verified with experimental and real time monitoring of volatile released by the mango.