Colorimetric Assay For Selenium And Tellurium In Environmental Samples

Recently,the rapid development of urbanization,industrialization and agricultural activities leads to trace elements as by-products of industry and human civilization.Interesting concentration of trace metals entered into the environment,posing a serious threat to the ecological environment.The investigation of the spatial and temporal distribution information of elements and their existing species in environmental samples is of great significance for understanding the migration,transformation and removal of environmental pollutants.At present,the main analytical methods for trace elements are atomic absorption spectroscopy,atomic fluorescence spectroscopy,inductively coupled plasma emission spectroscopy,and inductively coupled plasma mass spectrometry.These methods have higher sensitivity,but the instrument structure is more complicated,the analysis cost is high,and the experimental conditions are high,making it difficult to be applied for on-site rapid analysis of in environmental pollution events.Therefore,the development of simple and sensitive method applied in the field analysis is of great significance for sudden environmental events.In the past decade,gold nanoparticles have been widely used as a colorimetric sensing probe for the detection of organic compounds and inorganic ions.Gold nanoparticles based colorimetric assays eliminates the limitations of traditional laboratory analysis without using organic co-solvents,enzyme-linked reactions,photosensitizing dye molecules,and complex instrumentation.However,gold nanoparticles are susceptible to high salt and strong acid/base in the sample matrix,which undoubtedly reduces the selectivity of the analytical method and affects the accuracy of the analysis.The photochemical vapor generation technique means that in the presence of a low molecular weight organic compound,the sample solution is irradiated with ultraviolet light,and the element can be converted into a volatile form.The method has is green and with strong anti-interference ability,and is widely used as a new and efficient sample introduction method for atomic spectrometry.Therefore,we have established a new system for analysis of trace metal using photochemical vapor generation coupled with gold nanoparticles visualization.The specific work includes the following two aspects:Selenium is an indispensable nutrient element in the human body.However,excessive selenium may lead to poisoning to human being.In general,the toxicity of inorganic selenium is greater than that of organic selenium,and the toxicity of Se（IV）is greater than that of Se（VI）.Therefore,speciation of selenium in environmental samples can get better information for environmental impact and health risk assessment.In this study,the selective photochemical reduction of selenium was used to convert selenium into volatile H₂Se and into the gold nanoparticles solution,which led to the aggregation of gold nanoparticles and the color of its solution changed from red to blue for visual analysis.Se（IV）is selectively determined in the absence of photo-catalyst（TiO₂）;the total amount of Se（IV）and Se（VI）can be detected after the addition of the photo-catalyst,and the concentration of Se（VI）can be calculated by subtracting Se（IV）from the total Se concentration.The detection limit of the method can reach 6.0μg/L,which can meet the Se determination requirements（10μg/L）in water samples such as drinking water and farmland irrigation water.The method does not need to use expensive large-scale instruments,has the characteristics of simple method,green and high sensitivity,and does not require complicated sample pre-reduction process,and overcomes the elements that may be produced by the pre-reduction of concentrated hydrochloric acid and the process in the traditional selenium speciation analysis.The effect of morphological transformation and loss on the accuracy of the analysis.The sensitivity of the method is comparable to that of atomic absorption spectroscopy and inductively coupled plasma emission spectroscopy,but it can be used for on-site and rapid morphological analysis of selenium in environmental water.Te causes different organ failures in the human body.In recent years,with its wide application in rubber,petroleum,glass,medicine and solar cells,the potential environmental hazards have also attracted people’s attention.In this paper,we use a new system of nano-TiO₂ and iron ions synergistically,photo-catalysis for the PVG of Te and subsequently transfer the generated volatile species into AuNPs solution,leading to the color change of AuNPs.The detection limit of the method was 0.02μM by UV-vis detection.It’s worth mentioning that 0.1μM Te can induce an obvious color change,which can be directly observed with naked eyes.The method has the advantages of high sensitivity and simple operation and avoid pre-reduction process in conventional hydride generation.