Preparing Solutions as Molar Equivalents

It is common to use a solubility aid such as 1 molar equivalent (1eq.) of sodium hydroxide (NaOH) in the preparation of aqueous solutions of some amino acids. We generally recommend that a 100 mM sodium hydroxide solution is used to dissolve the active compound.

Protocol
Step 1.

Using the batch specific molecular weight (M.W.) of the compound, calculate the amount in grams that is required to prepare a 100 mM solution when 1L of solvent is added: (M.W. /10) = amount in grams (X)

Step 2.

From this, calculate the amount in grams required to prepare a 100 mM solution when 1 ml of solvent is added: (X /1000) = amount in grams (Y)

Step 3.

1 ml of the NaOH stock solution (100mM concentration) can now be added to this weight (Y) to dissolve the compound. In some cases warming of the solution or sonication may aid solubilization.

Working example

Glutamic acid (Cat. No. 0217) has a batch M.W = 147.13

For a 100 mM solution: M.W./10 = 14.7 g in 1L

The amount required to prepare 1 ml of a 100 mM solution:
14.7/1000 = 14.7 x 10-3 g in 1 ml
= 14.7 mg in 1 ml

Weigh 14.7 mg of glutamic acid

Add 1 ml NaOH (100 mM)

= 1 ml of a 100 mM solution of glutamic acid in 1eq. NaOH

This solution can then be further diluted (with water) to the required concentration.

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