Background absorption from certain substrates in graphite furnaces has been previously documented. This paper primarily investigates the wavelength characteristics of background absorption associated with 13, Sun, 3, æ°“, 33, and 33, as well as the effects of ashing temperature, atomization temperature, and evaporation time on this phenomenon. The study aims to enhance the accurate determination of ultra-trace impurities in rare earth compounds by understanding and mitigating these background absorption effects.
In the experimental section, reagents and instruments were carefully prepared. A solution containing 0.227882,3 was dissolved in 106,1 nitric acid, evaporated to dryness, and then redissolved in 1.5 mL of nitric acid before being diluted to a final volume of 5 mL using deionized water. Similar procedures were followed for preparing solutions of Sun Xin 033 and 3. All solutions contained either 0.3% nitric acid or 0.3% hydrochloric acid. The samples used in this study were provided by 99.991 and Waishan Pearl River Smelting 1.
The experiment was conducted using a 2380 atomic absorption spectrophotometer equipped with a xenon lamp as the light source, a slit width of 0.7, and a 1.1400 stone furnace. High-purity argon gas was used as the shielding gas, and each sample was analyzed twice. The detailed operation procedure for the graphite furnace is outlined in section 1.
Results showed that the matrix background absorption of LuCl3 exhibited clear wavelength-dependent behavior. The emission intensity of the xenon lamp was automatically adjusted to maintain consistency across different wavelengths. Background absorption was most significant in the short-wavelength range, gradually decreasing as the wavelength increased. At specific wavelengths, such as 33, a prominent background absorption peak was observed, while at other wavelengths, the background signal was minimal. For example, a background signal appeared at 190–240 nm within the first few seconds of measurement, and another between 290–400 nm after 258 seconds. Two background signals were detected in the 190–240 nm range, with the smaller one occurring earlier than the larger one.
The study also explored the effect of ashing temperature on background absorption. When the ashing temperature was set to 600°C, the initial peak during the atomization stage disappeared, but the ashing stage still showed some background absorption. At higher temperatures, such as 1600°C, most of the interfering components were removed during the ashing process, significantly reducing the background absorption during atomization.
Time-resolved measurements revealed that the background absorption signal appeared later when the atomization temperature was lower, leading to broader peaks and reduced peak heights. Using maximum power heating instead of standard heating minimized the impact of temperature on the timing and shape of the background absorption peaks, making it more suitable for accurate analysis.
Additionally, the study found that adding nitric acid as a matrix modifier helped reduce chloride interference. The background absorption peak height for 13 and 33 increased and decreased depending on the concentration of nitric acid added. Specifically, when the solution contained 2% nitric acid, the background absorption was reduced to 8%.
In conclusion, the background absorption of the ruthenium matrix shows distinct wavelength characteristics. By selecting appropriate wavelengths and converting the sample into nitrate or hydrate forms, the accuracy of trace impurity detection can be improved. Higher ashing temperatures reduce background absorption, and by choosing suitable atomization methods and recording times, certain background interferences can be minimized. This approach allows for better separation of the atomic absorption signal from the background, enhancing the overall analytical performance.
References:
Mo Shengwei. Background absorption of urine in graphite furnace atomic absorption spectrometry. Hua Tian and Xiong, waiting, He Hua and so on. High sensitivity atomic absorption spectroscopy and emission spectroscopy. Beijing Atomic Energy Press, 1981.
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