Research And Design Of A Phosphatespec-Trophotometric Detecting Systembased On Pulsating Variable Optical Path Length

The detection of phosphate in water is an important section in environmental monitoring. Though most widely used in laboratory, the spectrophotometry is difficult to meet the requirements of on site, on speed, batch and accuracy. The introduction of automatic analysis technology enables great improvement of traditional spectrophotometry in automated batch detection. Further, during the long-term online or in situ monitoring of phosphate in water, measurement errors are caused by various interferences, including drift of spectrophotometric light sources and sensors, mist on the light window or staining by colored complex. As the existing solutions to address the problem have not overcome the interference essentially, the practical application of spectrophotometry, especially in the long-term online or in situ monitoring of phosphate in water, still cannot meet the research or practical demands.According to such a status, based on the classic spectrophotometric detection, this paper proposes an innovative pulsating variable optical path length spectrophotometric detection method, and designs a pulsating variation of optical path length spectrophotometric detection device accordingly. Combined with automated analysis technology, it is a measurement system that can be used in the long-term online or in situ monitoring of phosphate in water to eliminate interference while ensuring measuring accuracy and stability. The content and innovations of this paper mainly include:1. A pulsating variable optical pathlength spectrophotometric detection method is proposed. Based on a comprehensive analysis of the interfering factors existing in the long-term online or in situ monitoring of phosphate in the water using traditional spectrophotometric detetion and an in-depth study of differential technology, we construct an interference model and conduct a mathematical analysis to put forward the pulse variable optical path length spectrophotometric detection method that is able to eliminate all the above-mentioned interferences.2. A pulsating variable optical path length spectrophotometric detection device is designed. This modular and miniaturized device can provide on-site and online measurement. Using constant-pressure variable optical path method, the main structure, together with stepper motor, machine screw, detection chamber, sensors and other components, can automatically adjust the optical path of the solution to be tested in the detection chamber through software control during the measuring process.The experimental results show that the biggest change of the absorbance is2%which achieves the best stability of the light source.3. A phosphate detection system is developed based on the pulsating variable optical path length spectrophotometric device and experimental verification is carried out using actual samples. Comparison of experimental results with the classical spectrophotometic method show that both the absorbance accuracy is the same ad0.01, while the long-term monitoring results show that the stability of the pulsating variable optical path length sepctrophotometric device is10times higher than traditional ones.Compared with traditional devices, this phosphate monitoring system based on pulse variable optical path length spectrophotometric detection method not only realizes the long-term on-line or in situ automatic monitoring, but also greatly enhances the anti-interference ability while guaranteeing the detection accuracy and stability. In sum, it is a system that can be widely used. Due to its ability to measure any nutrients that can be detected using spectrophotometry, it can be used in marine field as well as relevant environmental monitoring or industrial process detection, thereby making a great contribution to the development of optical analysis technologies and instruments.