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Principle of the phosphate analyzer testing method: Ions have different distribution coefficients between the stationary phase and the mobile phase. When the mobile phase carries the sample into the separation column, the various ions in the sample are separated due to their differing relative affinities for the ion exchange resin, and then they proceed to the suppressor. The function of the suppressor is primarily to reduce the background conductivity of the eluate, increase the conductivity response of the ions being measured, and remove cations from the sample. The solution then flows through a conductivity cell, where it is detected by a conductivity detector; this allows for the creation of chromatograms of various ions. The retention time is used for qualitative identification, while the peak height or peak area is used for quantitative determination of the ion concentrations. Next, let’s discuss the steps for operating the instrument: 1. Instrument calibration: Instrument calibration includes blank calibration and curve calibration. II. Methods for testing water samples. 1. Color development of the water sample to be tested: Pour 50 mL of the water sample into a plastic cup, add 5 mL of reagent, mix well, and let it stand for 3 minutes. 2. Measurement of water samples: (1) Perform a blank calibration. (2) With the instrument in the measurement screen mode, pour in the developed water sample to be tested; the instrument will then display the phosphate content of the currently measured water sample. (3) Once this value has stabilized and is confirmed to be valid, use the “+” or “–” keys to select the number of channels to which it should be stored, then press the “Store” key; the value will be automatically saved to the corresponding channels. (4) If the value is considered invalid, press the “Drain” button to empty the liquid and perform a blank calibration. With the instrument in the measurement mode, pour in the colored water sample to be tested, and the instrument will display the phosphate content of the current water sample. To make better use of the advantages of this device, it is necessary to pay attention to the relevant conditions when using it. 1. The instrument should be cleaned after long-term use: Open the instrument cover, remove the cuvette, soak it in a 5% hydrochloric acid solution to clean it thoroughly, and then use it again. 2. For each measurement, the water sample to be tested is injected in two portions, and the value displayed in the second injection is taken as the final value. 3. After each measurement, demineralized water should be injected and not drained.