🍶 0.5 M carbonate/bicarbonate (pH 8.75)

This protocols shows how to mix 0.5 M carbonate/bicarbonate buffer

🚛 Reagents needed 📦 :
Item Item article number Distributor Vendor
Sodium carbonate, anhydrous
223484 Merck SigmaAldrich
Sodium bicarbonate
S5761 Merck SigmaAldrich
UltraPure™ DNase/RNase-Free Distilled Water 10977035 ThermoFisher Invitrogen

The carbonate/bicarbonate anion system has two pKa values, one at 6.4 and one at 10.3. Therefore, at pH 8-9, you will have both carbonate and bicarbonate present. One simple way to make your buffer is to make two 100mM solutions, one of NaHCO3 and one of Na2CO3. You can then mix various proportions of the two until you get the proper pH.

 Make 0.5 M carbonate solution by adding 2.75 g in 50 mL nuclease-free water.

 Make 0.5 M bicorbonate solution by adding 2.1 g in 50 mL nuclease-free water.

 Combine 750 µL of carbonate solution into 23 mL of bicarbonate solution.

 Check pH that it is 8.75.

 Fill up to 50 mL with nuclease-free water.