How to Make Sodium Citrate Buffer

Two viales of sodium citrate
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Sodium citrate buffer is frequently used for RNA isolation, because it minimizes base hydrolysis of the RNA strands, making it invaluable for mRNA purification during genomic research, and for studying transcription. Citrate-based buffers also aid the detection of antigens in fixed tissue preparations, because they break the cross-links formed between the antigens and the fixation media.

With the following easy steps, one can create a sodium citrate buffer of pH 6 in under 10 minutes.

Two Options to Make the Buffer

There are two methods of making sodium citrate buffers, depending on the materials accessible to you.

METHOD ONE: If you have both citric acid and the conjugate base, create a stock solution of each by mixing 21 grams of citric acid in 1 liter of distilled water and 29.4 grams of sodium citrate in 1 liter of distilled water.

METHOD TWO: If you only have citric acid on hand, mix 2.1 grams in just under 1 liter of distilled water.

Mixing Citric Acid and Sodium Citrate Solutions

Mix 82 milliliters of the citric acid solution with 18 milliliters of the sodium citrate solution. To this, add enough distilled water to bring the volume of the mixture to slightly under 1 liter.

Adjusting the pH

While gently stirring the solution with a magnetic stirrer, use 1M sodium hydroxide to adjust the pH of the mixture to 6.0. Then, with a volumetric flask, add more distilled water to bring the final total volume of the solution up to exactly 1 liter.

What You Need to Make the Buffer

Few materials are required to make the sodium citrate buffer. With citric acid, one only needs 1M of sodium hydroxide, distilled water, and a calibrated pH probe. Sodium citrate is optional.

Making the buffer also requires a 1 liter graduated cylinder, a 1-liter volumetric flask, and three 1 liter media bottles. Lastly, you'll need a magnetic stir bar and a magnetic stirrer. All of these materials may be found at school or work-site laboratories and may also be purchased online or at specialty goods stores.