水溶液中硫酸根离子的拉曼光谱定量分析

拉曼光谱因其具有无损、非接触以及原位的技术优势被广泛应用于科学研究领域。但是,当前拉曼光谱主要应用于定性研究,即根据拉曼波数偏移进行物质分子的鉴别,相比之下,拉曼光谱定量分析则明显不足。因此,有必要进一步开展拉曼光谱定量方面的研究。根据拉曼光谱原理分析可知,拉曼光谱定量研究应当根据相对强度比进行,也就是在定量化过程中需要选择一个参考系,可以分为内标法和外标法。拉曼光谱定量可以根据被测分子与该参考系的拉曼强度比值进行,通过这个方法可以消除测试条件的影响。对水溶液而言,可将液态水的OH伸缩振动作为内标,进行拉曼光谱定量分析。本文研究了Na_2SO_4-H_2O,K_2SO_4-H_2O以及NaCl-Na_2SO_4-H_2O体系的拉曼光谱特征。通过将水分子的OH伸缩振动(2 750~3 900cm-1附近)拟合为两个高斯谱峰,并以ISO2-4/IW为参数来确定溶液中的硫酸根离子浓度,其中I_(SO_4~(2-))为硫酸根离子的特征峰强度,IW为水的两个高斯谱峰强度之和。实验结果表明,水溶液中SO_4~(2-)浓度与拉曼强度比I_(SO_4~(2-))/IW之间有较好的线性关系,其中,R~2=0.997 73,符合定量要求。据此,本文应用拉曼光谱定量分析,建立了一种相对快速、准确测量水溶液中SO_4~(2-)浓度的方法。

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 elimi-nates the influence of the measurement conditions .For aqueous solution ,it is reasonable to treat the OH stretching band of wa-ter as an internal standard to determine the solute concentrations in aqueous solution .The Raman spectra of Na2SO4-H2O , K2 SO4-H2 O and NaCl-Na2 SO4-H2 O 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 ISO2 -4 /IW is used to determine the molarity of sulfate in aqueous solution , where ISO2 -4 represents the intensity of sulfate band and IW represents the sum of the two sub-bands of Raman OH stretching bands of water .Therefore ,Raman spectroscopy can be utilized to measure the SO2 -4 concentrations in aqueous solutions .