Detection of Diazinon Organophosphates Using Magnetoelastic Sensor

Abstract

Organophosphates (OP) have been used to kill insects in many areas such as homes and workplaces, especially in agricultural pest control [1]. In many people, the remains of OP can lead to many health problems to range from paralysis to death. For this reason, it is very important to detect OPs, which is the most important way of passage to the human organism, as a sensitive, fast, and cheap way. Nowadays, conventional OP detection is carried out by techniques such as mass spectroscopy, gas chromatography, and high-performance liquid chromatography. Although these methods give accurate and sensitive results, they require time-consuming processes such as sample preparation, solid-phase extraction, and comparison of sample peaks with references. Moreover, the cost of these methods is quite high. Therefore, the development of an alternative method as sensitive, fast, practical and cheap for detection of OPs was carried out in this study.The system used in the detection of OPs is a magnetoelastic sensor (MES). Magnetoelastic sensors are preferred because of their low cost, disposable application, wireless and easier to use. Magnetoelastic materials begin to vibrate (shorten and elongate) when exposed to a time-varying (AC) magnetic field. The vibration frequency of such samples varies depending on the geometry, elastic coefficient and mass (density) of the sample [2]. In magnetoelastic sensors, the amount of mass usually deposited on the sensor surface causes a shift in the resonance frequency and the shift in the magnetoelastic measurement system is measured. In this way, the mass accumulated on the sensor surface can be measured. It is important that the sensor surface is functionalized according to the type of molecule being detected. The magnetoelastic sensor will be more precise and superior if it measures a very low mass change. Therefore, enlarging the sensor surface area makes a significant contribution to the sensitivity of the sensor. In this context, electrospun nanofibers were coated on the sensor surface in order to increase the surface area of magnetoelastic sensors for the first time within this study. Within the scope of this project, 2826MB (Fe40Ni38Mo4B18) amorphous ferromagnetic ribbons with 35 mm long and 5 mm in width were used as MES.Then, the nanofibers were functionalized with glutaraldehyde (GA) in order to covalently bind acetylcholinesterase (AChE) enzyme to the surface. The resonance frequency of the functionalized amorphous strip was measured to be around 59 000 Hz. OP in the 10% EtOH solution was dripped with a micropipette on the surface of the functionalized MES then allowed drying. It was observed that the EtOH solution evaporate and the remaining OP covalently binds the acetylcholinesterase (AChE) enzyme.When 50 ppm OP in 10% EtOH solution were dropped, a decrease of approximately 22 Hz was observed in the resonance frequency at 500 A/m DC bias magnetic field. Figure 1 shows the measured resonance frequency change when different amounts of OP were dropped onto the MES. As can be seen, MES shows a linear change according to the amount of OP measured in the range of 0-150 ppm in 10% EtOH solution.To determine whether the frequency shift comes only from the OP, only 10% EtOH solution was dripped onto the functionalized MES surface in different amounts and it was found that no shift in the frequency had occurred.AcknowledgmentThis work was supported by TUBITAK with 119F144 project number. **