Abstract：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.
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