Phosphate buffer recipe


Recipe

Sodium phosphate

1 M sodium phosphate buffer (pH 6.0-7.2)

Mixing 1 M NaH2PO4 (monobasic) and 1 M Na2HPO4 (dibasic) stock solutions in the volumes designated in the table below results in 1 L of 1 M sodium phosphate buffer of the desired pH. To prepare the stock solutions, dissolve 138 g of Na2HPO4•H2O (monobasic; m.w. = 138 g) in sufficient H2O to make a final volume of 1 L and dissolve 142 g of Na2HPO4 (dibasic; m.w. = 142 g) in sufficient H2O to make a final volume of 1 L.

Volume (mL) of 1 M NaH2PO4 Volume (mL) of 1 M Na2HPO4 Final pH
877 123 6.0
850 150 6.1
815 185 6.2
775 225 6.3
735 255 6.4
685 315 6.5
625 375 6.6
510 490 6.8
450 550 6.9
390 610 7.0
330 670 7.1
280 720 7.2

0.1 M sodium phosphate buffer (pH 7.4)

Add 3.1 g of NaH2PO4•H2O and 10.9 g of Na2HPO4 (anhydrous) to distilled H2O to make a volume of 1 L. The pH of the final solution will be 7.4. This buffer can be stored for up to 1 mo at 4°C.

0.1 M sodium phosphate buffer (from 1 M stocks) at 25°C

To prepare 1 L of 0.1 M sodium phosphate buffer of the desired pH, the following mixtures should be diluted to 1 L (final volume) with H2O.

pH Volume (mL) of 1 M Na2HPO4 Volume (mL) of 1 M NaH2PO4
5.8 7.9 92.1
6.0 12.0 88.0
6.2 17.8 88.2
6.4 25.5 74.5
6.6 35.2 64.8
6.8 46.3 53.7
7.0 57.7 42.3
7.2 68.4 31.6
7.4 77.4 22.6
7.6 84.5 15.5
7.8 89.6 10.4
8.0 93.2 6.8
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