Design And Realization Of Portable Polarization Detection System For Heavy Metal Fluorescence

Heavy metal ions in the water environment are difficult to be decomposed,transmitted through the food chain,and eventually accumulated in the human body,causing great harm to human health.In order to prevent the pollution of heavy metal ions from intensifying,the development of heavy metal ion concentration detection instruments is a hot spot of current research.There are many kinds of mature heavy metal ion detection equipment,but most of them rely on large-scale imported equipment for laboratory testing,and the equipment is expensive,It is not conducive to the introduction of community environmental protection departments.Based on this,the subject proposes a method that combines fluorescence polarization detection technology with embedded control technology,and successfully developed a heavy metal fluorescence polarization detection system to detect the concentration of heavy metal ions in aqueous solutions.The specific work is as follows:1)According to the fluorescence polarization immune technology and fluorescence polarization detection kinetic analysis,the overall scheme design of the heavy metal fluorescence polarization detection system was completed,and the market demand was analyzed according to the system function and performance,thus,the characteristics,index parameters and working process of fluorescence polarization detection system for heavy metals are determined.2)using confocal optical system scheme of easy to realize miniaturization and to improve the excitation light energy utilization ratio and beam collimation,using total internal reflection structure design of the free surface collimating lens,lens model and optical simulation,the results show that more free-form surface collimating lens in the intensity of illumination uniformity and energy utilization efficiency were significantly enhanced.Then the filter,polarizer,dichromatic mirror,objective lens,focusing lens and photodetector are selected,and the mechanical design of optical structure is completed,which lays a foundation for the accurate acquisition of fluorescence polarization signal.3)In order to realize the miniaturization of the circuit,the hardware circuit is integrated on a motherboard with STM32 as the control core,the motherboard includes the main control circuit,the fluorescence polarization signal acquisition circuit,the stepper motor drive circuit,the light source drive circuit,the serial communication circuit,and the data storage circuit,power circuit,etc.Two human-computer interaction schemes are designed,one is to develop a touch-sensitive USART HMI human-computer interaction screen;the other is to develop a PC software based on C Sharp language to meet the needs of on-site and off-site scenarios.4)Aiming at the noise problem of the fluorescence polarization signal,the moving average filtering algorithm is used to complete the de-noising of the fluorescence polarization signal on the embedded control system.The empirical mode decomposition denoising algorithm is used in PC software to denoise the polarization signal and good denoising effect is achieved.Aiming at the bimodal characteristics of heavy metal fluorescence polarization signal,an automatic peak seeking algorithm was proposed to calculate the fluorescence polarization value.5)After completing software and hardware design and installation debugging,set up an experimental platform for fluorescence polarization detection of heavy metals,Firstly,complete the calibration experiment of Cu²⁺,Zn²⁺and Cd²⁺concentration of the prototype,and then conduct precision test,repeatability test,stability test,minimum detection limit test and comparison test of the prototype.The fluorescence polarization detection system for heavy metals developed in this paper is convenient to carry,simple to operate and low cost to use.The experimental results show that the linear correlation coefficient of the system is high,the system detection error is less than 4%,the repeatability error is less than 2%,the system stability is good,and the system detection limit is low,meet the requirements of the system design.