| Analysis and determination of trace heavy metal ions and inorganic pollutants in water environment are important parts of modern analytical chemistry.Currently,large-scale equipments are only suitable for use in the laboratory,but can not be used in on-site analysis and determination.With increasingly severe water pollution incidents,there are demands of on-site and portability trends for analytical techniques.In this paper,two types of micro fiber chemical sensors were constructed based on absorption detection by combining the optical fiber and spectroscopic techniques.With advantages of small size,flexibility,multiplexing capability,low propagation loss of signal and resistance to electromagnetic interference,the fabricated sensors have been successfully applied to real-time and on-line analysis of trace pollutants in water environment.A small volume fiber-optic sensor was developed and integrated with the lab-on-valve(LOV)system.As a result,a micro fiber-optic sensor lab-on-valve(FOS-LOV)system was successfully established by combining with the sequential injection analysis technology.The FOS-LOV system has been applied to detection of nitrite and residual chlorine in water.The incubation time for reaction,flow rate and the other detection conditions were optimized.The influence of temperature and foreign ions was studied.Real sample analysis and recovery tests on real samples were investigated under the selected conditions.The results were compared with the results obtained by traditional methods.The experimental results showed that the consumption of samples and reagents was effectively reduced due to the automatic mesoscopic flow control features of LOV and high sensitivity of fiber-optic detection,and the analysis speed and the detection sensitivity were greatly improved.As a result,an automatic,accurate,rapid and online analysis method has been successfully established for pollutants determination.A fiber-optic interface analysis method was developed and the fiber-optic evanescent wave sensor was constructed based on the evanescent wave generated on the fiber surface.The evanescent wave produced on the fiber surface could interact with the sensing reagents and produce absorption change.The presence of trace pollutants could cause sensitive changes of evanescent wave signal.Then the trace pollutants could be determinated by colorimetric method and evaluated by absorbance according to Beer’s law.By combining with flow injection analysis techniques,the fiber-optic evanescent wave sensor has been applied to sensitive detection of fluoride content in tea samples and the Cr(VI)content in wastewater samples.The incubation time for reaction,flow rate and the other detection conditions were optimized.The influence of temperature and foreign ions was studied.Real sample analysis and recovery tests on real samples were investigated under the selected conditions.The results were compared with the results obtained by UV spectrophotometer.The results showed that by utilizing the evanescent wave produced on the fiber surface to interact with the sensing reagent,the detection and sensing elements were both integrated on the fiber.As a result,the sensor fabrication was greatly simplified and successfully miniaturized through avoiding complicated optical arrangements.A miniature and portable analysis method combined with optical fiber was successfully presented.In this paper,two miniaturized fiber-optic chemical sensors were constructed and solved the problems of large volume and difficult application for traditional analysis device.This work successfully developed real-time and in situ analysis technology of trace pollutants in water samples.Meanwhile,the sensors were modularly designed to avoid complex sample pretreatment,simplify preservation and transportation of water samples.As a result,this work greatly improved the analysis technology for on-site environmental monitoring,and successfully established an analytical platform for the accurate and sensitive detection of trace substances. |
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