Magnesium chloride Stock Solution

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Stock Solution Preparation Guide – Magnesium Chloride (MgCl₂)

Magnesium chloride (MgCl₂) is a highly water-soluble inorganic salt widely used in molecular biology, biochemistry, and cell biology. Mg²⁺ acts as an essential cofactor for many enzymes, including DNA polymerases, RNA polymerases, and restriction enzymes.

Magnesium chloride is commercially available in both anhydrous and hydrated forms. Anhydrous MgCl₂ is strongly hygroscopic and rapidly absorbs moisture from air, making accurate weighing difficult. Therefore, magnesium chloride hexahydrate (MgCl₂·6H₂O) is most commonly used for preparing laboratory stock solutions.

Objective

Preparation of 100 mL of 1 M Magnesium Chloride stock solution.

Composition

• 1 M Magnesium chloride (MgCl₂)

Required Materials

• Magnesium chloride hexahydrate (MgCl₂·6H₂O)
• Deionized / distilled / Milli-Q water
• Measuring cylinder
• Conical flask or beaker (≥ 250 mL)
• Magnetic stirrer (optional)

Procedure

Wear appropriate personal protective equipment (lab coat, gloves, and safety goggles) and follow institutional laboratory safety guidelines.

• Step 1
  Weigh 20.33 g of MgCl₂·6H₂O (MW 203.30) and transfer it into a beaker. Add approximately 80 mL of deionized or Milli-Q water and mix until fully dissolved.
• Step 2
  After complete dissolution, adjust the final volume to 100 mL with deionized or Milli-Q water. Mix thoroughly.
• Step 3
  Sterilize the solution by autoclaving for 20 minutes at 121–124 °C (15 psi, liquid cycle).

Note: Sterilization can also be performed by filtration using a 0.22 µm membrane filter under aseptic conditions.

Storage

Magnesium chloride solutions are moderately unstable over long periods. Store at 4 °C for short-term use. For long-term storage, aliquot and freeze at −20 °C. Avoid repeated freeze–thaw cycles.

Available Reagents