The CRC Handbook of Biochemistry gives the composition of McIlvaine buffer as a mixture of 0.1 molar citric acid and 0.2 molar disodium phosphate.
Depending on the pH you want, you mix varying amounts of the two components together. For example, 98 ml of citric acid + 2 ml of Na2HPO4 gives pH 2.2,42 ml of citric acid + 58 ml Na2HPO4 gives pH 5.6, and 2.75 ml citric acidand 97.25 ml Na2HPO4 gives pH 8.0 (all pH determinations given at 21 C).
Mcilvaine's Buffer SystemSP, Aug 2005
A citrate/phosphate buffer system that can be volumetrically set for pH in a wide range (2.2 to 8), and is therefore useful for enzyme kinetic studies, etc.
To prepare 20 ml of the buffer, mix 0.2 M disodium hydrogen phosphate and 0.1 M citric acid as shown below.
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