Sodium Phosphate Buffer has a buffering range between 5.8 – 8.0. By mixing monobasic (NaH2PO4) and dibasic (Na2HPO4) sodium phosphate solutions in the right proportion, you can prepare a sodium phosphate buffer of a desired pH.
To prepare 1M Sodium Phosphate Buffer of desired pH, mix 1M solution of sodium phosphate monobasic (NaH2PO4) and 1M solution of sodium phosphate dibasic (Na2HPO4) as suggested in the following table.
| Preparation of 1L of 1M Sodium phosphate buffer of desired pH | ||
| Final pH of the solution(Final volume: 1000 ml) | Volume of 1 M NaH2PO4 (in ml) | Volume (mL) of 1 M Na2HPO4(in ml) |
| 5.8 | 920 | 80 |
| 5.9 | 900 | 100 |
| 6.0 | 877 | 123 |
| 6.1 | 850 | a150 |
| 6.2 | 815 | 185 |
| 6.3 | 775 | 225 |
| 6.4 | 735 | 265 |
| 6.5 | 685 | 315 |
| 6.6 | 625 | 375 |
| 6.7 | 565 | 435 |
| 6.8 | 510 | 490 |
| 6.9 | 450 | 550 |
| 7.0 | 390 | 610 |
| 7.1 | 330 | 670 |
| 7.2 * | 280 | 720 |
| 7.3 | 230 | 770 |
| 7.4 | 190 | 810 |
| 7.5 | 160 | 840 |
| 7.6 | 130 | 870 |
| 7.7 | 105 | 895 |
| 7.8 | 85 | 915 |
| 7.9 | 67 | 933 |
| 8.0 | 53 | 947 |
| * To prepare 1000 ml solution of 1M Sodium phosphate buffer of pH 7.2, mix 280 ml of 1M Sodium phosphate monobasic and 720 ml of Sodium Phosphate dibasic. | ||
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