Application of Atomic Fluorescence Spectrometry for Mercury Analysis in Environmental Monitoring
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Application of Atomic Fluorescence Spectrometry for Mercury Analysis in Environmental Monitoring
With the development of modern science and technology, various high-tech detectors and instruments have been continuously improved, which has played a significant role in the development of scientific research and the realization of people's healthy life. In particular, the extensive application of atomic fluorescence spectrometry in the laboratory and in life plays an important role in the detection of healthy water quality and qualified food. Through the analysis of the experimental results, this paper optimizes the detection conditions of mercury in water by atomic fluorescence spectrometry, so that it can be applied accurately and quickly in real life.
With the introduction of atomic fluorescence spectrometry in the mid-20th century, its spectral analysis technology has been widely used in various fields due to its low detection limit, high sensitivity, simple operation and relatively low instrument price. The use of atomic fluorescence spectrometry for the analysis of elements such as arsenic, antimony, mercury, tin and selenium plays an important role in water quality analysis, food testing and environmental testing. Especially in environmental monitoring, mercury is a mandatory item in urban surface water, groundwater, drinking water and water quality weekly reports. The mercury is measured by atomic fluorescence spectrometry, and the detection conditions are optimized to enable accurate and rapid determination of mercury in water.
1 experimental principle
After the reducing agent potassium borohydride solution is added to the acidic medium, the mercury is reduced to gaseous atomic mercury, which is directly introduced into the quartz atomizer by the carrier gas and mixed with the gaseous hydride and the argon or carrier gas. Entering the atomizer, argon and hydrogen are formed by a special ignition device to form a hydrogen argon flame, and finally the atom to be tested is atomized. The focus of the emission characteristic line is excited by the element to be tested, so that the atom to be detected in the hydrogen argon flame is excited, and the obtained fluorescent signal is accepted by the solar blind photomultiplier tube, and then demodulated and amplified, and finally The data processing system produces the results.
2 experimental operation
2.1 Main measuring instruments and conditions
Mainly used instrument AFS-830 dual-channel atomic fluorescence spectrometer and high-intensity mercury hollow cathode lamp. The experimental conditions were humidity 68% and room temperature 20 °C. The measurement methods used are reading mode, standard curve method, and peak area. 2.2 reagent and instrument value adjustment
The water used in the experiment was ultrapure water, and the concentration of the potassium borohydride solution was reduced to 0.1% because the potassium borohydride reducing agent used in the mercury was not reduced to form gaseous atomic mercury by the formation of a hydride. Since the mercury content in surface water is low, it is usually near the detection limit, so the linear range of the concentration of the standard curve should be reduced accordingly. In order to increase the sensitivity of the instrument and increase the intensity of the fluorescence, the negative voltage of the photomultiplier tube can be increased to 300V. The mercury lamp has a lamp current of 30 mA and an atomizer height of 10 mm. The hydrochloric acid selected for this experiment is excellent grade pure hydrochloric acid or high purity grade hydrochloric acid. The standard and standard solution are all made of pure grade nitric acid. The choice of concentrated nitric acid, potassium permanganate and concentrated sulfuric acid is excellent grade. The sodium hydrogen sulfide and hydrochloric acid are analytically pure.
2.2 Selection of potassium borohydride concentration
Potassium borohydride, as a reducing agent in the experiment, has an important influence on the fluorescence intensity of mercury. When the carrier gas flow rate is constant, different concentrations of potassium borohydride will affect the peak and peak time of the mercury fluorescence signal. In this experiment, 0.50 g/L of mercury standard solution was used, and the concentration of potassium borohydride was in the range of 0.1% to 1.0% in the time of 20 s reading without delay. The experimental results show that in the range of 1.0%-0.5%, the mercury fluorescence signal increases with the increase of potassium borohydride concentration, because the lower concentration of potassium borohydride can not make the mercury far away, and will affect the steam. The efficiency produced.
2.3 Selection of potassium permanganate concentration
According to the research of the relevant professionals on the mass transfer reaction of potassium permanganate to absorb gaseous mercury, the efficiency of mercury absorption by different concentrations of potassium permanganate solution is also different. In the range of 0.005mmo1 / L, the mercury absorption rate increases with the increase of potassium permanganate concentration, but when C (MnO4-) is more than 0.5mmo1 / L, even if the concentration of potassium permanganate is increased, mercury absorption There is no significant increase in the rate, and high concentrations of hydrochloric acid and high concentrations of potassium permanganate result in high reagent blanks, which lowers the detection limit. In addition, the sulfuric acid solution (1+9) has an obvious effect on the efficiency of mercury absorption by potassium permanganate solution. Therefore, the potassium permanganate concentration selected in the experiment should be 0.5mmo1 / L, and the mercury absorption rate is about 95%.
3.4 Time stability analysis of instrument preheating
Pipette 10 ng/mL of mercury standard solution 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, 5.00 mL, 6.00 mL into a 100 mL volumetric flask and dilute to the corresponding scale using 3% nitric acid solution. After the instrument was warmed up for 20 minutes, the blank value was measured, and after 25 minutes, the blank value was measured. After that, a standard curve was measured every 5 minutes, and a total of 20 curves were created, sharing 125 minutes. It can be seen from the test that when the mercury concentration value is at 50 ug/L, it can be basically stabilized after one hour of starting. The slope of the curve does not change much after 60 minutes of power on. Therefore, the determination of mercury should be started in advance, and it must be longer than the preheating time for the determination of selenium and arsenic. Preheating is best for 60-90 minutes, and the stability is better.
It can be seen from the above experimental analysis that the mercury should be preheated for 60-90 minutes in the determination of mercury. In addition, it should be noted that the sample is fully oscillated and higher after being placed in the instrument chamber for 35 minutes. In the measurement of the sample, it should be shaken first. In addition, the choice of the type and amount of reagent has a great influence on the accuracy and precision of its determination. If it is to measure the mercury content in clean surface water, it is reasonable to use the color correction method for pretreatment.
3 experimental results and discussion
The choice of reagents for mercury measurement by atomic fluorescence spectrometry has a great influence on the accuracy and precision of the experiment, and the choice of auxiliary equipment also has an impact on the experimental results. Finding the best combination can improve the accuracy of experimental measurement data and provide more theoretical support for practical applications.
4 conclusion
The use of atomic fluorescence spectrophotometry to measure mercury in life can create a better living environment for people's lives. Especially in food safety and drinking water monitoring, it is related to the safety of people's lives and property. The atomic fluorescence photometer is a product of the new era. Its operation and application should be continuously explored to find better conditions for use to achieve the optimal combination. In addition, we should also pay attention to the choice of instrument model. Under the development of high technology, we pay attention to the innovation and improvement of advanced instruments, so that they can play a greater role and serve more social life.