Preparation MOPS Stock Solution

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Stock Solution Preparation Guide – MOPS Buffer (1 M, pH 7.4)

MOPS (3-(N-morpholino)propanesulfonic acid) is a zwitterionic biological buffer with a useful pH range of approximately 6.5–7.9. It is soluble in water and commonly used for biochemical assays, cell culture media, and protein purification applications.

Objective

Preparation of 500 mL of 1 M MOPS buffer, pH 7.4 stock solution.

Composition

• 1 M MOPS (C₇H₁₅NO₄S) buffer adjusted to pH 7.4

Required Materials

• MOPS (Free acid, MW = 209.26 g/mol)
• Deionized / Milli-Q water
• 10 N NaOH for pH adjustment
• Measuring cylinder
• Conical flask or beaker
• Magnetic stirrer
• Sterile 0.22 µm filter unit for sterilization
• PPE: gloves, goggles, lab coat

Procedure

• Step 1
  Weigh out **104.65 g** of MOPS free acid and add it to ~400 mL deionized water in a conical flask. Stir until completely dissolved.
• Step 2
  Slowly add **10 N NaOH** while monitoring with a calibrated pH meter to adjust the solution to **pH 7.4**.
• Step 3
  Once the desired pH is reached, make up the volume to **500 mL** with deionized water and mix thoroughly.
• Step 4
  Sterilize by filtration through a **0.22 µm** membrane into a sterile container. Autoclaving is not recommended as it may degrade the buffer.

Storage: Store the buffer at **4 °C** in a light-protected (amber) bottle to minimize yellowing over time.

Available Reagents