Quantitative Analysis of NO-3，SO2-4，ClO-4 With Water as Internal Standard by Raman Spectroscopy
WANG Gan-lin1, LIU Qian1, LI Ding-ming1, YANG Su-liang1*, TIAN Guo-xin1, 2*
1. Department of Radiochemistry, China Institute of Atomic Energy, Beijing 102413, China
2. Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China
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, SO2-4, 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 Asalt/AH2O and csalt/cH2O 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 csalt and conform to the relationship: csalt=ARS/(1+BRS), where RS=Asalt/AH2O. 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 cNaNO3=18.8RS/(1+0.6RS) (R2=0.999 1), cNa2SO4=20.2RS/(1+1.0RS) (R2=0.998 8), and cNaClO4=15.0RS/(1+0.7RS) (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.
王淦麟，柳 倩，李定明，杨素亮，田国新. 基于水内标的NO-3，SO2-4，ClO-4拉曼光谱定量分析研究[J]. 光谱学与光谱分析, 2022, 42(06): 1855-1861.
WANG Gan-lin, LIU Qian, LI Ding-ming, YANG Su-liang, TIAN Guo-xin. Quantitative Analysis of NO-3，SO2-4，ClO-4 With Water as Internal Standard by Raman Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(06): 1855-1861.
[1] BAI Xue，LI Ding-ming，CHANG Zhi-yuan，et al(白 雪，李定明，常志远，等). Journal of Nuclear and Radiochemistry(核化学与放射化学)，2015，37(3)：143.
[2] Liu Q，Zhang Q，Yang S，et al. Dalton Transactions，2017，46(39)：13180.
[3] Zhang Q，Zhu H，Chang Z，et al. Analytical Methods，2016，8(7)：1549.
[4] Conrad J，Sasidharanpillai S，Tremaine P R. The Journal of Physical Chemistry B，2020，124(13)：2600.
[5] Wong M K，Shariff A M，Bustam M A. RSC Advances，2016，6(13)：10816.
[6] Pelletier M J. Applied Spectroscopy，2003，57(1)：20A.
[7] Aarnoutse P J，Westerhuis J A. Analytical Chemistry，2005，77(5)：1228.
[8] Bai X，Li D M，Chang Z Y，et al. Journal of Radioanalytical and Nuclear Chemistry，2015，305(2)：643.
[9] Duraipandian S，Knopp M M，Pollard M R，et al. Analytical Methods，2018，10(29)：3589.
[10] Li L，Xin Z，Luan Z，et al. Journal of Raman Spectroscopy，2018，49(10)：1722.
[11] Wu J，Zheng H. Chemical Geology，2010，273(3-4)：267.
[12] Kauffmann T H，Fontana M D. Sensors and Actuators B: Chemical，2015，209：154.
[13] Yuan X，Mayanovic R. Applied Spectroscopy，2017，71(10)：2325.
