激光拉曼光谱技术是水下原位探测酸根离子浓度的强有力工具, 建立一套适用于海洋环境、 基于拉曼光谱技术的定量分析方法对实时了解海洋化学信息具有重要意义。 本文在实验室条件下, 以SO2-4和HCO-3系列浓度水溶液及近海海域的海水为样品, 532 nm激光作为激发光源, 模拟原位探测方式采用侵入式光学探头采集拉曼光谱。 分别采用内定标法、 多元线性回归法(MLR)、 偏最小二乘法(PLS)和基于主导因素的PLS法对光谱数据进行定量分析。 研究结果表明, 采用以1 640 cm-1水分子O—H振动谱峰为内标峰的内定标法预测待测离子浓度, 预测误差均相对较大, 定标曲线线性相关系数不高; 采用多元线性回归法, 定标曲线的线性相关系数有较大提高, 在一定程度上提高了定量分析的精度; 采用酸根拉曼峰强度、 酸根峰面积、 水峰强度、 水峰面积作主导因素结合PLS法预测配置溶液中SO2-4和HCO-3浓度的定标曲线相关系数R2分别为0.990和0.916, 对待测样30 mmol·L-1的SO2-4预测相对误差为3.262%, 对20 mmol·L-1的HCO-3预测相对误差为5.267%。 以海水中SO2-4为分析对象时, 与离子色谱法预测的28.01 mmol·L-1进行对比, 以上四种定标方法的研究结果表明, 主导因素结合PLS法优于其余三种分析方法, 其均值相对误差降低为1.128%。 因此, 采用水的拉曼信号作为主导因素结合PLS法预测水溶液中的酸根离子浓度时能有效提高定量分析的精度, 并可应用于现场和原位探测中的定标。

Laser Raman spectroscopy as an in situ analytical technology can enable detailed investigation of the ocean environment. It is necessary to set up a quantitative analysis method based on laser Raman spectroscopy to understand the marine status in situ. In the laboratory investigations, varied concentration of HCO-3, SO2-4 and coastal waters of Qingdao are taken as the samples, operating 532 nm of laser, using fiber optic probes to simulate detection mode in situ. Raman spectra are analyzed using the method of internal standard normalization, multiple linear regression(MLR), general Partial Least Squares(PLS) and PLS based on dominant factor respectively in data processing. It was found that correlation coefficients of calibration curves are not high in internal standard normalization method and predicted relative errors on the prepared samples are much high, so internal standard normalization method cannot be effectively used in the quantitative analysis of HCO-3, SO2-4 in the water. And with the multiple linear regression, the analysis accuracy was improved effectively. The calibration curve of PLS based on dominant factor showed that the SO2-4 and HCO-3 of pre-made solution with correlation coefficient R2 of 0.990 and 0.916 respectively. The 30 mmol·L-1 of SO2-4 and 20 mmol·L-1 of HCO-3 in two target samples were determined with the relative errors lower than 3.262% and 5.267% respectively. SO2-4 in the coastal waters as the research object was analyzed by above-mentioned methods, comparing with 28.01 mmol·L-1 by ion chromatography. It was demonstrated that PLS based on dominant factor method is superior to the rest of the three analysis methods, which can be used in situ calibration, with the mean relative error about 1.128%. All the results show that analysis accuracy would be improved by the PLS based on dominant factor method to predict concentration of acid radical ions.