Preparation of 5 mM Ammonium Acetate Buffer
Material Preparation
1. ** Ammonium Acetate ($NH_4CH_3COO $) **: Analytical purity to ensure the purity of the reagent to ensure the quality of the buffer.
2. ** Deionized Water **: Use high-purity deionized water to avoid the impact of impurities on the pH value and properties of the buffer.
3. ** Electronic Balance **: The accuracy needs to meet the requirements of accurate weighing of ammonium acetate. Generally, a balance that can be accurate to 0.001 g is selected.
4. ** Volumetric Flask **: Select the appropriate specification volumetric flask, such as 1000 mL volumetric flask, for bandwidth evaluation buffer.
5. ** Glass rod **: used to stir the solution to accelerate the dissolution of ammonium acetate.
6. ** pH meter **: used to accurately measure and adjust the pH of the buffer.

Operation steps
1. ** Calculate the amount of ammonium acetate **: According to the formula $n = C\ times V $ (where $n $is the amount of substance, $C $is the amount of substance concentration, $V $is the solution volume), to prepare 1000 mL of 5 mM ammonium acetate buffer, the amount of ammonium acetate substance $n = 5\ times 10 ^ {-3} mol/L\ times 1 L = 5\ times 10 ^ {-3} mol $. If the molar mass of ammonium acetate is 77.083 dollars g/mol $, then the required mass of ammonium acetate $m = n\ times M = 5\ times 10 ^ {-3} mol\ times 77.083 g/mol\ approx 0.385 g $.
2. ** Weigh ammonium acetate **: Use an electronic balance to accurately weigh 0.385 g of ammonium acetate and place it in a clean beaker.
3. ** Dissolve ammonium acetate **: Add an appropriate amount of deionized water to the beaker containing ammonium acetate and stir with a glass rod to promote the rapid dissolution of ammonium acetate.
4. ** Transfer Solution **: After the ammonium acetate is completely dissolved, carefully transfer the solution along the glass rod to a 1000 mL volumetric flask. Rinse the beaker and glass rod with a small amount of deionized water 2-3 times, and transfer the rinsing liquid to the volumetric flask together to ensure that the solute is fully transferred.
5. ** bandwidth evaluation **: Slowly add deionized water to the volumetric flask until the liquid level is close to the scale line 1-2 cm. Use a rubber head dropper to add deionized water dropwise until the concave liquid surface of the solution is tangent to the scale line.
6. ** Mix well **: Cover the volumetric flask cork and repeatedly reverse the volumetric flask to fully mix the solution.
7. ** pH detection and adjustment (if necessary) **: Use a pH meter to measure the pH value of the prepared buffer. The pH value of ammonium acetate buffer is generally close to the neutral range. If the pH value deviates from expectations, you can carefully add dilute acetic acid or dilute ammonia water dropwise for fine-tuning, stir while adding dropwise, and continuously measure with a pH meter until the desired pH value is reached.

In this way, the 5 mM ammonium acetate buffer has been prepared and can be used for subsequent related experiments.