基于水内标的NO-3，SO2-4，ClO-4拉曼光谱定量分析研究

doi:10.3964/j.issn.1000-0593(2022)06-1855-07

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Abstract Internal standard is often required when using Raman spectroscopy for quantitative analysis due to the poor reproducibility of the Raman spectrum. In aqueous solutions, the stretching vibration Raman peak of water at 2 700~3 900 cm^-1 has a strong intensity and may be used as an internal standard, but the interaction of water and solute will cause the shape of the water stretching vibration Raman peak to change. In addition, the concentration of water will also change with the change the solute concentration. When the solute concentration is high, the water concentration needs to be corrected. Taking these two factors into consideration, quantitative analyses of NO^-₃, SO^2-₄, ClO^-₄ in aqueous solutions with Raman spectroscopy are investigated, focusing on evaluating water as an internal standard. The Raman spectra of different concentrations of NaNO₃，Na₂SO₄，NaClO₄ solutions show that with the increase of salt concentration, the Raman peak of water in the range of 2 700~3 900 cm^-1 presents a trend that the left shoulder drops and the right shoulder rise. However, there exists a good linear relationship between A_salt/A_H₂O and c_salt/c_H₂O in NaNO₃，Na₂SO₄，NaClO₄ solutions, where A represents the area of the Raman peak and c represents the concentration, and the R² of the three fitting curves are 0.999 1, 0.999 1, 0.999 4, respectively. This indicates that the Raman scattering coefficients of acid ions and water do not change or change in the same proportion. So, although the shape of the water Raman peak having changed, the feasibility of water as an internal standard is not affected. After introducing the correction of the concentration of water, it is theoretically deduced that c_salt and conform to the relationship: c_salt=AR_S/(1+BR_S), where R_S=A_salt/A_H₂O. In a wide concentration range from 0.1 mol·L^-1 to near saturation, the standard working curves for NaNO₃, Na₂SO₄, and NaClO₄ are obtained to be c_NaNO₃=18.8R_S/(1+0.6R_S) (R²=0.999 1), c_Na₂SO₄=20.2R_S/(1+1.0R_S) (R²=0.998 8), and c_NaClO₄=15.0R_S/(1+0.7R_S) (R²=0.999 8), respectively. The limit of detection (LOD) of NaNO₃, Na₂SO₄ and NaClO₄ are found to be 0.008 0, 0.005 2 and 0.007 3 mol·L^-1, respectively. On the basis that the shape change of the water Raman peak does not affect its feasibility as an internal standard, when there are two salts in a solution, a water concentration correction for the second salt can be made to improve the quantitative analysis based on the standard curves for the single salt solutions. However, the correction result is limited when the second salt concentration is too large, and the first salt concentration is relatively small because the accuracy of the Raman peak area of the first salt will be affected due to the too large Raman intensity of the second salt.

Key words：Water internal standard; Raman spectroscopy; NO^-₃，SO^2-₄，ClO^-₄; Quantitative analysis

Received: 2021-04-29 Accepted: 2021-06-22

ZTFLH:

O657.37

Corresponding Authors: YANG Su-liang, TIAN Guo-xin E-mail: gtian@ciae.ac.cn; ysl79@ciae.ac.cn

Cite this article:

WANG Gan-lin,LIU Qian,LI Ding-ming, et al. Quantitative Analysis of NO^-₃，SO^2-₄，ClO^-₄ With Water as Internal Standard by Raman Spectroscopy[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(06): 1855-1861.

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2022)06-1855-07 OR https://www.gpxygpfx.com/EN/Y2022/V42/I06/1855