Research On Smartphone-based Image Sensing Technology For Detecting Common Pollutants In Water

Water environment monitoring is of great significance to ecological security and human health.Traditional instrumental analysis techniques rely on expensive instruments and professional operators,limiting their use in economically underdeveloped countries and regions and in remote areas.Aiming at the above problems,this paper studied the image sensing technology based on smart phones,and carried out the optimization of detection conditions and method establishment of common pollutants in water based on this technology.The main research results are as follows:(1)Built the optical path system with the camera of the smartphone as the sensor,integrated the colorimetric detection system of the smartphone through 3D printing,and inspected and tested the performance of the system.The results show that the wavelength range of smart phone spectral detection is 400 nm~700 nm,and the resolution is 0.29 nm/pixel.The light absorption of the sample conforms to the principle of color complementation.The sensitivity of each index standard curve established by the grayscale model is better than other models,and the correlation coefficient of the standard curve is >0.99.The LOD of ammonia nitrogen was 0.025mg/L,the relative standard deviation of repeated tests was <7.3%,and the relative error with the laboratory spectrophotometer test results was <6.3%.The LOD of turbidity was 2 NTU,the relative standard deviation of repeated tests was <6.4%,and the relative error with the spectrophotometer test results was <4.9%.The LOD of orthophosphate was 0.016 mg/L.The LOD of fluoride was 0.14 mg/L.Based on the above hardware system,I participated in the development of a supporting mobile App,and demonstrated the application in the monitoring of surface water environment in suzhou city.The field test results showed that the detection results of ammonianitrogen and turbidity were basically consistent with the results of the monitoring station,indicating that the system had practical application value in the field.(2)Focusing on the optimization of sample pool structure with the colorimetric detection system of smart phones,the original quartz colorimetric dish was replaced by a paper-based microfluidic device.The precision of wax printing and the vertical and horizontal diffusion of wax were tested in the paper-based microfluidic device.The results show that the performance of the printer is good.When the wire width is0.7mm,the wax can permeate completely.The effect of camera parameters on signal was studied by adjusting the height and exposure time of mobile phone.The results show that the image signal is best when the distance between the phone and the paper chip is 85 mm and the image color restoration degree is high.The grayscale signal was used to test ammonia nitrogen and orthophosphate,and it was found that the linear relationship between the grayscale and the concentration of the substance was satisfied.The linear range of ammonia nitrogen was 0~25 mg/L,and the linear range of orthophosphate was 0~100 mg/L.(3)A strategy of quantitative detection of escherichia coli by smart phone imaging after using magnetic beads to capture bacteria was proposed.The coupling efficiency of magnetic beads with different particle sizes on proteins was studied.It was found that the coupling amount of 2 m magnetic beads was 5~38 times that of 50 nm when the protein was sufficient.The culture of escherichia coli showed that escherichia coli was in the logarithmic growth period between 2 and 11 h,and the OD value of the bacterial solution was linearly correlated with the number of colonies,R2=0.98.E.coli in the logarithmic growth period was selected to prepare suspension solution,with OD value of 0.55,which could be kept stable after being placed at room temperature for one hour.This paper discusses the conditions of the immune magnetic beads in capturing bacteria,and determines that the optimal magnetic separation time of the magnetic beads is 10 min,and the optimal time to capture bacteria is 30 min.When 0.075 mg of magnetic beads are added,the capture efficiency can reach up to66%,and the signal-to-noise ratio of the closed magnetic beads can reach 2.