根据苯甲酰脲类农药在紫外光的照射下能够发出荧光的机理,设计了一种基于CCD(电荷耦合器件)的检测该类有机农药残留的光纤荧光测量系统。该系统以脉冲氙灯为激发光源,利用光纤探测和传输荧光,采用线阵CCD代替传统的光电倍增管作为荧光信号的光电检测元件,同时配备A/D 高速数据采集卡,实现了单片机控制下荧光信号的光电转换以及数据采集,进而实现了对卡死克和盖虫散(氟铃脲)农药浓度的测量。实验结果表明,在激发波长分别为290 nm 和345 nm 时,卡死克和盖虫散的荧光强度分别在360 nm 和418 nm 处达到最大,最低检出限分别为12 μg/L 和20 μg/L。在25~1 000 μg/L 范围内,荧光强度和溶液浓度基本呈线性关系。该测量系统灵敏度高,线性范围宽,可以满足荧光检测的要求。

According to spectral characteristics that benzoylurea pesticides can emit fluorescence as they are irradiated by UV rays,an optical fiber fluorescence measurement system based on Charge-coupled Device (CCD) was designed for pesticides residue. The system adopted a pulsed xenon lamp as excitation light-source,employed optical fibers to transmit and detect fluorescence,and used linear-array CCD instead of traditional photomultiplier tube as photoelectric detection device of the fluorescence signal. Moreover,it was equipped with high-speed A/D data acquisition card,implemented photoelectric conversion of the fluorescence and data acquisition under the control of a singlechip,and further achieved the concentration measurement of flufenoxuron and hexaflumuron. The result indicates that,when the excitation wavelength is 290 nm for flufenoxuron and 345 nm for hexaflumuron respectively,the fluorescence intensity of the former appears maximum as the wavelength is 360 nm and that of the latter appears maximum as the wavelength is 418 nm. The minimum detecting limits are 12 μg/L and 20 μg/L respectively. The fluorescence intensity is directly proportional to solution concentration in the range of 25~1 000 μg/L. This measurement system has several characteristics such as high sensitivity and wide linear range,which can meet the demand of fluorescence detection.