[The Quantitative Analysis of Raman Spectroscopy to Sulfate Ion in Aqueous Solution]

As a non-destructive and non-contact method, Raman spectroscopy has been widely applied in many research fields. Based on vibrational wavenumber, Raman spectroscopy is usually applied to determine the molecular species. Therefore, Raman quantitative analysis is necessary. In this study, according to the theoretical analysis of Raman intensity, Raman quantitative measurement should be fulfilled by relative intensity ratio, which can be divided into internal and external standards. This eliminates the influence of the measurement conditions. For aqueous solution, it is reasonable to treat the OH stretching band of water as an internal standard to determine the solute concentrations in aqueous solution. The Raman spectra of Na₂SO₄-H₂O, K₂SO₄-H₂O and NaCl-Na₂SO₄-H₂O are recorded in the paper. In addition, the Raman OH stretching band of water can be fitted into two Gaussian sub-bands. The intensity proportion I(SO₄²⁻)/I(W) is used to determine the molarity of sulfate in aqueous solution, where I(SO₄²⁻) represents the intensity of sulfate band and I(W) represents the sum of the two sub-bands of Raman OH stretching bands of water. Therefore, Raman spectroscopy can be utilized to measure the SO₄²⁻concentrations in aqueous solutions.