CN-116793971-B - Method for measuring aluminum content by atomic absorption spectrometry of graphite furnace

Abstract

The invention provides a method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace. The method comprises the steps of preparing an aluminum series calibration solution added with alkali metal nitrate, measuring absorbance by using a graphite furnace atomic absorption spectrometer, drawing a standard curve by taking the measured absorbance as an ordinate and the aluminum content in the aluminum series calibration solution added with the alkali metal nitrate as an abscissa, adding the alkali metal nitrate into a sample to be measured, measuring the absorbance by using the graphite furnace atomic absorption spectrometer, and calculating according to the standard curve to obtain the aluminum content in the sample to be measured. The method can fully atomize the aluminum element, improves the measurement accuracy, solves the problem of different atomization rates of sample water and calibration solution, and masks the interference of other metal oxides.

Inventors

• WANG RUI
• LI PENG
• LI YONGLI
• WU HUACHENG
• ZHOU WEIQING
• LI ZHICHENG
• LU LU
• ZHOU ZILONG
• LI CHAO

Assignees

• 国网冀北电力有限公司电力科学研究院
• 国家电网有限公司

Dates

Publication Date

20260512

Application Date

20230519

Claims (11)

1. 1. A method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace, which comprises the following steps: (1) Preparing an aluminum series calibration solution added with alkali metal nitrate, measuring the absorbance of the aluminum series calibration solution added with the alkali metal nitrate by using a graphite furnace atomic absorption spectrometer, and drawing a standard curve by taking the measured absorbance as an ordinate and the aluminum content in the aluminum series calibration solution added with the alkali metal nitrate as an abscissa, wherein the volume of the aluminum series calibration solution added with the alkali metal nitrate is taken as a reference; (2) Adding alkali metal nitrate into a sample to be measured, wherein the adding amount of the alkali metal nitrate is 0.005-0.03mmol/L based on the volume of the sample to be measured, the alkali metal nitrate comprises sodium nitrate and/or potassium nitrate, the absorbance of the alkali metal nitrate is measured by using a graphite furnace atomic absorption spectrometer, and then the aluminum content in the sample to be measured is calculated according to the standard curve obtained in the step (1); The working conditions for measuring absorbance by utilizing a graphite furnace atomic absorption spectrometer comprise detection wavelength of 309.3nm, ashing temperature of 700-800 ℃ and time of 20-30s, atomization temperature of 2300-2350 ℃ and time of 4-5s.
2. 2. The method according to claim 1, wherein the aluminum series calibration solution added with alkali metal nitrate is prepared by respectively taking different amounts of aluminum standard solution, adding proper amounts of nitric acid and alkali metal nitrate, and respectively metering the volume with water to obtain the aluminum series calibration solution added with alkali metal nitrate with aluminum content of 1-100 mug/L.
3. 3. The method according to claim 2, wherein the aluminum content in the alkali metal nitrate added aluminum series calibration solution is 10 μg/L to 60 μg/L.
4. 4. The method of claim 2, wherein the concentration of aluminum in the aluminum standard solution is 1000 μg/L.
5. 5. The method of claim 1, wherein the sample to be assayed comprises a water sample.
6. 6. The method of claim 5, wherein the sample to be assayed is a filtered water sample.
7. 7. The method of claim 1, wherein step (2) further comprises adding nitric acid to the sample to be assayed for digestion.
8. 8. The method according to claim 7, wherein the added nitric acid is present in the sample to be assayed in an amount of 0.15-0.2mol/L.
9. 9. The method according to claim 1, wherein a matrix improver is further added to each of the alkali metal nitrate-added aluminum series calibration solution and the sample to be measured.
10. 10. The method of claim 9, wherein the matrix modifier comprises magnesium nitrate.
11. 11. The method according to claim 9, wherein the matrix improver is added in an amount of 300 to 700 μg/L based on the volume of the alkali metal nitrate added aluminum series calibration solution and the volume of the sample to be measured, respectively.

Description

Method for measuring aluminum content by atomic absorption spectrometry of graphite furnace Technical Field The invention relates to a method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace, and belongs to the technical field of metal content detection. Background The method for measuring aluminum by using high-temperature graphite furnace to electrically heat and atomize the sample is widely applied to the technology of water quality assay and supervision. In the prior art, a method for measuring the aluminum content by using a graphite furnace atomic absorption spectrometry is to utilize an atomizer which is made of graphite materials and is in the shape of a tube, a cup and the like, heat a sample to 2500 ℃ by using current, measure absorbance at 309.3nm wavelength and calculate the aluminum content. However, when an amphoteric substance such as aluminum is measured, a problem of unstable results occurs, and the lower the aluminum content in the sample, the more remarkable the problem of instability. The method for measuring aluminum by using the high-temperature graphite furnace to electrically and thermally atomize the sample comprises the steps of treating the calibration solution and treating the sample water. In general, the process of treating the calibration fluid comprises dissolving pure aluminum in hydrochloric acid and diluting to a certain volume, adding nitric acid into the diluted solution to digest the diluted solution to form the calibration fluid, adding a matrix improver (typically magnesium nitrate), and drawing a standard curve. The final product formed after the calibration solution and the matrix improver are fully ashed is a mixture of Al 2O3 and magnesium oxide, and atomic excitation is carried out by taking the mixture of Al 2O3 and magnesium oxide as a final state. The sample water was digested after filtration and during the test, a solid mixture was formed after ashing. Because the sample water contains even a small amount of other metal ions, other metal oxides in the mixture are relatively high in the solids formed by ashing. The final state of aluminum atom excitation is then excited as a mixture of Al 2O3 or as another mixture of aluminum. According to the solid mixture melting point principle, the melting point of a mixture containing other metal oxide impurities is lower than that of pure Al 2O3, and the melting point varies greatly according to the type of impurities. The melting point of Al 2O3 pure is 2050℃and the boiling point is 2980 ℃. The existing graphite furnace atomic absorption method needs to consider the temperature resistance and stability of a graphite tube, and is not suitable for taking an excessive test temperature, and the test temperature of aluminum element is generally 2500 ℃. The boiling point of magnesium oxide is 3600 ℃ and has little effect on the reduction of the boiling point of Al 2O3. The higher the atomization rate of the substance, the closer the measured value of the graphite furnace atomic absorption method is to the true value, and the reaching of the boiling point of the substance is the maximum excitation factor of atomization. In the prior art, on one hand, the boiling point requirement of aluminum can not be met when the calibration solution is tested, the atomization rate is very low, the slope of a formed standard curve is very low, and under the condition of the same aluminum ion concentration, the absorbance of the standard curve and the absorbance of a sample have larger deviation, so that larger measurement error is caused. On the other hand, the atomization rate of the sample to be detected is uncertain due to the presence of interference of other ions. Therefore, the existing method for measuring the aluminum content by using the atomic absorption spectrum of the graphite furnace has at least two problems, namely that the maximum atomization rate of aluminum cannot be excited, and that the different atomization rates of the calibration solution and the detection sample exist. These two factors are the main causes of inaccurate measurement of aluminum in the industry. Therefore, the development of a novel method for measuring the aluminum content by atomic absorption spectrometry of a graphite furnace becomes one of the problems to be solved urgently in the field. Disclosure of Invention In order to solve the technical problems, the invention aims to provide a method for measuring the aluminum content by atomic absorption spectrometry of a graphite furnace. The method can fully atomize the aluminum element, improve the measurement accuracy, solve the problem of different atomization rates of sample water and calibration solution, and mask the interference of other metal oxides. In order to achieve the above object, the present invention provides a method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace, comprising the steps of: (1) Preparing an alumi