孙俊, 唐宝文, 周鑫, 姚坤杉, 胡双齐, 张林. 作物叶片表面农药残留的便携式检测仪器的设计与试验[J]. 农业工程学报, 2021, 37(7): 61-67. DOI: 10.11975/j.issn.1002-6819.2021.07.008
    引用本文: 孙俊, 唐宝文, 周鑫, 姚坤杉, 胡双齐, 张林. 作物叶片表面农药残留的便携式检测仪器的设计与试验[J]. 农业工程学报, 2021, 37(7): 61-67. DOI: 10.11975/j.issn.1002-6819.2021.07.008
    Sun Jun, Tang Baowen, Zhou Xin, Yao Kunshan, Hu Shuangqi, Zhang Lin. Design and test of a portable detection instrument for pesticide residues on crop leaves[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(7): 61-67. DOI: 10.11975/j.issn.1002-6819.2021.07.008
    Citation: Sun Jun, Tang Baowen, Zhou Xin, Yao Kunshan, Hu Shuangqi, Zhang Lin. Design and test of a portable detection instrument for pesticide residues on crop leaves[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(7): 61-67. DOI: 10.11975/j.issn.1002-6819.2021.07.008

    作物叶片表面农药残留的便携式检测仪器的设计与试验

    Design and test of a portable detection instrument for pesticide residues on crop leaves

    • 摘要: 针对现有的农药残留检测仪器只能检测水溶液体系中的农药残留和检测对象较为单一的问题,该研究以不同植物叶片啶虫脒农药残留为研究对象,探究了利用荧光强度检测叶片表面农药残留的可行性,设计了一款叶片表面农药残留的便携式检测仪器。首先,通过啶虫脒农药叶片表面喷洒试验,采集叶片的荧光光谱并进行特征分析,发现啶虫脒农药的最佳激发波长和最佳发射波长分别为355 和500 nm,从而确定光源和光电信号接收源的特征波长分别为350和500 nm。然后,通过获取最佳光源照射角度以及光照距离,优化光路结构减少叶片表面杂散光的干扰。同时,设计相关检测电路(光源电路、信号调理电路、控制电路等)测出表征反射光强度的电压值,构建电压值与农药残留值之间的线性方程,设计便携式检测仪对农药残留进行检测。结果表明:1)荧光强度与农药浓度在1~5 mg/L的范围内成正比;2)确定了检测仪器最佳光照角度为45o,光源和待测叶片之间的最佳垂直距离为3.46 cm;3)方程决定系数达到了0.875,均方根误差为0.405 mg/L。该研究所设计的便携式荧光光谱仪能够快速、准确、无损检测叶片表面农药残留。

       

      Abstract: Fluorescence has unique luminescence characteristics. The combination of excitation light and emission light can greatly reduce the interference of background signals and greatly improve the sensitivity of the detection system. Many scholars at home and abroad obtain the optimal excitation and emission wavelengths of the analyte based on the principle of photoluminescence of fluorescent substances, and have developed miniaturized, low-cost dedicated instruments. However, the current portable instruments which focus on detecting pesticide residues in the solution system cannot realize directly detection pesticide residues on the surface of vegetable leaves. In this study, a feasible model for pesticide residues and fluorescence intensity on the leaf surface was proposed, and a portable detection instrument for pesticide residues on the leaf surface was designed by optimizing the light path structure to suppress the interference of stray light on the leaf surface. Firstly, the best excitation wavelength and best emission wavelength of acetamiprid pesticide in standard solution and three plant leaves were determined as 350 and 500 nm, respectively. An LED with a central wavelength of 350 nm and a maximum drive current of 100 mA was selected as the excitation light source, and a photodiode with a peak response range from 480 to 580 nm was used as the photoelectric detection device. A filter with a center wavelength of 500 nm was used to only let through the emission wavelength of the acetamiprid pesticide pass to reduce the interference of the secondary spectrum. Then the optimal parameters of the optical path are determined. The fluorescence experiments results showed that the fluorescence intensity excited by acetamiprid pesticide on the leaf surface was the highest when the light Angle was 45°. By calculating the optical path size, it was found that the illumination of the blade was the largest when the direct distance from the LED laser source to the blade was 4.89 cm and the vertical distance was 3.46 cm. In addition, in view of the diffuse reflection problem of the light source illuminating the surface of the blade, a diffuse reflection device was designed to achieve the maximum absorption of light energy. The control circuit, driving circuit and detection circuit were designed according to the requirement of weak fluorescence signal detection. A signal detection system was designed with STM32 chip as the main control chip to collect the voltage signal of the detection circuit, and the pesticide residue value was calculated according to the working curve of pesticide residue value. The PWM wave was output to modulate the LED light source and the difference between the frequency of detecting light and the frequency of ambient light can suppress the interference of ambient light to the light source. Then, SPI and I2C communication protocols were used to communicate with AD acquisition chip and OLED display screen to realize real-time detection of pesticide residues and real-time display of pesticide residues. Finally, the calibration equation was established and a portable detector was designed to detect pesticide residues. The measuring instrument was calibrated and tested.The determination coefficient of the calibration equation reached 0.875, and the root mean square error is 0.405 mg/L. The portable fluorescence spectrometer designed in this study can quickly, accurately and non-destructively detect pesticide residues on the surface of leaves, which provided a reference for the development of a more universal portable detection instrument.

       

    /

    返回文章
    返回