氯离子作为一种性质活跃的阴离子, 广泛分布在水溶液中。 氯离子含量是评价水质优劣重要参数之一, 它的高低对食品安全、 工业生产以及腐蚀控制等方面都有不可忽视的影响。 因此, 快速准确的测定水溶液中氯离子含量对优化生活环境、 促进工业发展具有现实意义。 拉曼光谱法是通过分析分子对光的散射效应进行定量检测的技术, 它以所需样品少、 灵敏度高和适用于水中检测等优点广泛应用于各种物质的定性和半定量检测中, 而用于定量检测的案例就比较少。 尝试以炼油厂含硫污水中的氯离子为检测目标, 利用激光拉曼光谱技术结合硝酸银比浊法建立一套全新的测定氯离子浓度的检测方法。 该方法是在提前加入硝酸的情况下, 以丙酮作为稳定剂, 使不同浓度的氯离子溶液与硝酸银反应生成均匀稳定的氯化银胶体, 然后使用小型拉曼光谱仪采集氯化银胶体的拉曼光谱图, 对光谱图进行平滑去噪、 基线校正, 再用高斯分峰拟合技术对拉曼光谱进行处理, 得到每个高斯峰的峰强度、 峰面积以及半峰宽等特征信息, 考察这些特征信息和氯离子浓度之间的关系。 实验结果表明: 常温常压下, 拉曼光谱在1 050和1 635 cm^-1处高斯拟合的特征峰强度之比与氯离子的浓度在0.1~4 mg·L^-1范围内具有良好的线性关系, 相关系数为0.991 4, 标准偏差系数(RSD)低于5%, 回收率在98.02%~103.3%之间, 具有良好的准确度和重复性, 符合定量检测要求, 可用于预测氯离子的浓度。 为了确定硝酸、 硝酸银、 稳定剂、 静置时间等因素对实验结果的影响, 该研究还进行了系统的优化并确定了最佳的实验条件。 最优实验条件为: 在25 mL水中依次加入2 mL硝酸(1+1), 2 mL丙酮, 2 mL硝酸银溶液(0.1 mol·L^-1), 静置时间为15 min。 因此, 拉曼光谱结合硝酸银比浊法测定水中氯离子浓度的方法是可行的, 这种方法易于操作, 所需样品量少, 后期可应用于在线监测, 在水质检测、 腐蚀控制、 物质分析等领域具有广阔的应用前景。

As an active anion, the chloride ion is widely distributed in various aqueous solutions. Chloride ion concentration is an important parameter to evaluate water quality, which has a great impact on food safety, industrial production and corrosion control. Therefore, rapid and accurate determination of chloride ion content in aqueous solution have practical significance for optimizing the living environment and promoting industrial development. Raman spectroscopy is a kind of spectral detection method based on Raman scattering effect. It is widely used in qualitative and semi-quantitative detection of various substances with the advantages of a few samples required, high sensitivity and is suitable for aqueous solution detection, but few cases were reported for quantitative detection. A new method was proposed in this paper for the determination of chloride ion concentration in aqueous solution based on laser Raman spectroscopy combined with silver nitrate turbidimetry. The silver nitric was firstly dipped into the aqueous solution, with acetone as a stabilizer, to make chloride ions with different concentrations react with it to generate a uniform and stable silver chloride colloid, and then the Raman spectrum of the silver chloride colloid was collected using the small Raman spectrometer. After smoothing, de-noising and baseline correction of the Raman spectrum, the Gaussian peak fitting technique was used to fit the Raman spectrum curve. The characteristic parameters of each gaussian peak, such as peak intensity, peak area and half peak width, were obtained, and the relationship between these characteristic parameters and chloride ion concentration was determined. The experimental results show that under normal temperature and atmospheric pressure, the ratio of the peak intensity of the Gaussian fitting at 1 050 and 1 635 cm^-1 has a good linear relationship with the concentration of chloride ions, and the detection range of chloride ion concentration is 0.1~4 mg·L^-1. The correlation coefficient of the linear equation is 0.9914. The relative standard deviation is less than 5%, and the recovery rate is between 98.02%~103.3%, which implies the proposed method has good accuracy and repeatability, and is suitable for quantitative detecting requirements. In order to determine the effects of factors such as nitric acid, silver nitrate, stabilizers, and standing time on the experimental results, the systematic optimization of the measurement method was carried out to determine the best measurement conditions. The optimal experimental conditions were as follows: 2 mL of nitric acid (1+1), 2 mL of acetone, and 2 mL of silver nitrate solution (0.1 mol·L^-1) were successively added to 25 mL of water, and the standing time was 15 min. Therefore, the proposed method of determining the chloride ion concentration in aqueous solution based on Raman spectroscopy combined with silver nitrate turbidimetry is feasible. This method is simple in operation and has a small amount of sampling. It has broad application prospects in water quality detection, corrosion control, substance analysis and other fields.