Preparation of Ammonium Acetate Solution
To prepare 5 mM/L of ammonium acetate solution, prepare the necessary equipment, such as an accurate balance, a clean volumetric flask, a glass rod, and a beaker.

Weigh an appropriate amount of ammonium acetate solid on a balance. This amount needs to be accurately calculated according to the concentration of 5 mM/L and the volume of the solution to be prepared. After weighing, place in a clean beaker.

Inject an appropriate amount of distilled water into the beaker, stir it lightly with a glass rod, and promote the instant dissolution of ammonium acetate solids. When it is completely dissolved, slowly pour the solution along the glass rod into the corresponding volume of the bottle.

Then rinse the beaker and glass rod several times with a small amount of distilled water, and the rinsing solution is also injected into the volumetric bottle to avoid solute loss. Then add distilled water to the volumetric bottle, and when the liquid level is close to the scale line, use a rubber head dropper to add dropwise until the concave liquid level of the solution is tangent to the scale line.

Cover the volumetric bottle, turn it upside down repeatedly and shake it well to make the solution concentration uniform. In this way, the preparation of the ammonium acetate solution of 5 mM per liter is completed, which can be used for subsequent experiments.