This part specifies the detection method of chlorine content in bottled water, using the flow injection Ion selective electrode method. It is suitable for the determination of chlorine content in Encasement drinking water and bottled natural mineral water. First, the sample and the total ion strength regulator are diluted according to a certain volume, and then the flow injection Ion selective electrode method is used for detection. The linear relationship between the electromotive force and the log value of the chloride ion activity is used to establish the standard Linear dispersion, and then the external standard method is used for quantification. The reagents and materials used include anhydrous potassium nitrate, total ion strength regulator, chloride ion standard stock solution, standard working solution, and 0.45 μm aqueous filtration membrane.