Research On Optical And LAPS Sensors Detection Methods And Instruments For Heavy Metals In Water

In recent years,the economy of China has a leaping development,which leads to a serious heavy metal pollution in the water environment.Heavy metal pollution not only has a great impact on human health,but also cause a serious damage to the ecological environment.Therefore,our country has paid more and more attention to the detection of the heavy metal.There are many mature methods can be used,but these methods have many shortcomings such as bulky volume,long testing time and high cost of detection.So they are not suitable for the on-site testing of the heavy metals.In this paper,the method of detecting heavy metals based on spectrophotometry and Light Addressable Potentiometric Sensor(LAPS)was studied.This paper introduced the current situation of heavy metal pollution in the water environment,several major methods of the heavy metal detection as well as the development and application of LAPS.Then,an automatic instrument based on spectrophotometric for detecting copper ions,a miniaturized analysis instrument based on LAPS and a multi-channel LAPS detection system were designed.Finally,the H+ diffusion image based on LAPS detection system was explored.The main work and innovations of this paper are as follow:1.An automatic detection instrument for copper ion based on spectrophotometry was designed.In this paper,the detection method of Cu2+ in the water environment based on spectrophotometry was studied.The transistor was used to control the opening and closing of the peristaltic pump,and the photoelectric sensor was used to detect the droplets.Besides,the prototype of the automatic detection instrument was designed combined with an optical detection system that can adjust the light intensity automatically.The injection system and the best testing conditions of the instrument were analyzed.A good linear curve of Cu2+ was obtained.The results showed that the instrument completed the accurate injection of solution,and the automatic detection of Cu2+.The detection limit of Cu2+ was 6?g/L,which is lower than that of standard instrument.2.A miniaturized analytical instrument based on LAPS was designed to realize the detection of heavy metals.In this paper,the instrument adopted AD630 to achieve synchronous demodulation.And the square wave multiplier demodulation of the measured signal was achieved,thereby,reducing the DC drift which generated by multiplication analog circuits.And a low-pass filter with a time constant of 300ms and a decay rate of 12dB/oct was designed to achieve lock-in amplification.The LED excitation light source and its signal generation circuit were designed,and the analysis and control software was programmed.The miniaturized analytical instrument based on LAPS was completed.The detection of Cu2+ was realized by immobilizing the sensitive membrane of Cu2+on the surface of LAPS.Experiment results showed that the instrument was small and convenient with the function of detecting heavy metals.3.A multi-channel LAPS detection system is designed,and the algorithm of two phase lock-in amplification is implemented to realize multi-parameter detection.In this paper,a multi-channel LAPS detection system based on data acquisition(USB-6211)was designed,which included multi-channel light source to stimulate different LAPS.The software for this system was designed to realize the algorithm and synchronous multi-parameters detection.The Butterworth filter was also used as the pre-band-pass filter in the algorithm.The two phase lock-in amplification was realized by multiplying the sinusoidal signal,the elliptic low-pass filter and averaging the results.The system realized simultaneous detection of Pb2+ and H+.The experimental results showed that the algorithm of two phase lock-in amplification can detect multi-channel LAPS signals very well and realized multi-parameter detection based on LAPS.4.The detection of H+ diffusion image based on LAPS detection system is explored.In this paper,a X-Y scanning control system based on MAC6000 and an H+dynamic diffusion image detection system based on LAPS were developed,and the scanning control software and analysis algorithm were programmed.The H+ diffusion process was dynamic detected by immobilizing the agar substrate on the LAPS and scanning the H+ diffusion image.