NH3-NOperating procedures for ion electrodes
AStandard solution preparation
1. Dry a small amount of NH4Cl in the cabinet at a temperature of 100 ℃ for 2 hours. Take it out and cool it to room temperature in a dryer.
2. Accurately measure 3.8190 g of NH4Cl using an analytical balance. (Accurate to 0.1mg)
3. Dissolve fully in ammonia free solution (the same below) and then transfer all to a 1000 ml volumetric flask.
4. Dilute with water to the mark. This is a 1000mg/L NH4-N mother liquor (Can be stored in a cold and dark place for at least 6 months)
BStandard usage liquid preparation
1.Dilute 10.00ml of mother liquor to 1000ml. This is 10.00mg/L (can be stored in a cold and dark place for at least one month)
2. Dilute 100.0ml of standard solution 1 to 1000ml, which is 1.00mg/L (can be stored in a cold and dark place for at least one month)
CPreparation of ion strength adjustment solution (amount added)10％）
Weigh 20.0g NaOH and 18.6g Na2EDTA into a beaker, dissolve them in a small amount of ammonia free water, and dilute to 100ml. This is a 5.0mol/L NaOH and 0.5 mol/L Na2EDTA solution.
DCorrection steps
1. Take two small beakers, add 50.0ml of 10.0 mg/L and 1.00 mg/L respectively, and then add 5.00ml of ion strength adjustment solution separately.
2. Unscrew the electrode and add 2.0 ml of electrolyte (0.1 mol/L NH4CL) to the membrane head, then tilt and tighten.
3. Soak the electrode in 1.00mg/L standard solution for a few minutes.
4. Connect the host and turn it on. Insert the electrode into a 1.0 mg/L standard solution.
5. Press the M key until the screen displays ISE.
6. Press the cal key, the screen prompts, press the up and down keys and Enter key to move the cursor to the concentration bar, press the Enter key and up and down keys to enter the concentration of 1.00/mgL, and enter the water temperature.
7. Move the cursor to Continue and press Enter to start calibrating the screen's potential. Once stable, prompt for the second concentration. Place the electrode into the second beaker.
8. Use the Enter and Up/Down keys to enter a concentration of 10.0/mgL, enter the water temperature, which is the same as * times. Press Continue to continue 2-point calibration. After the potential stabilizes, the screen prompts. Use the Enter and Up/Down keys, with the cursor at exit 2 point cal, and press Enter. The screen displays the correction slope, press enter to confirm, and then press the M key to return to the testing mode.
9. Measure 50ml of sample with a concentration of 0.1-100 mg/L to be tested, add 5.00ml of ion strength adjusting solution, place the electrode in, start the test, and record the concentration value when the reading stabilizes.