(157af) Analysis of Organophosphate Residue Detection on SOLID Surface Using QCM-D As BIO-Sensing Platform

Detection of residual organophosphates in food is of paramount importance in current scenario. The understanding of interaction of pesticides on chemically modified surface is the backbone of biosensor fabrication. Quartz crystal microbalance with dissipation (QCM-D) is one of the most efficient techniques to analyze the interaction of organic molecules with silane modified surfaces making it desirable bio-sensing platform.

In this report, we have studied the real time adsorption of pesticide phorate and malathion on silica coated quartz crystal of QCM-D. The interaction study was first monitored on gold coated and unmodified silica coated crystal as reference. Further self-assembled monolayer was created on silica crystal using n-propyltrimethoxy silane (PTMS), octyltrimethoxy silane (OTMS), N-(3-(trimethoxysilyl)propyl) aniline and diethoxymethyl phenyl silane. The interaction study was also monitored by using atomic force microscopy (AFM). Amount of pesticide adsorbed on surface was evaluated in terms of the mass and thickness change of quartz crystal which is calculated from frequency change using Sauerbrey equation. Low value of dissipation factor (∆D) corresponds to stronger binding of pesticide which the result is obtained for OTMS modified surface. The overall results indicate that OTMS modified surface contributes mostly to the dissipation changes (∆D) or acoustic ratio (∆D/∆f). This surface shows largest amount of pesticide adsorption both for phorate and malathion which is correlated with the more hydrophobicity of the surface confirmed by contact angle measurements. The diethoxymethyl phenyl silane modified silica crystal also shows significant mass change for phorate as the phenyl group facilitates interaction with sulfur of pesticide molecule. Further verification was done by Raman spectroscopy. This interaction study may be utilized to fabricate sensors for pesticide detection.