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 1000 ml of 0.1M Sodium Phosphate Buffer of desired pH, mix 1M sodium phosphate monobasic (NaH2PO4), 1M sodium phosphate dibasic (Na2HPO4), and water as suggested in the following table.
| Preparation of 1L of 1M Sodium phosphate buffer of the desired pH | |||
| Final pH of the solution (Final volume: 1000 ml) | Volume of 1 M NaH2PO4 | Volume (mL) of 1 M Na2HPO4 | Water |
| 5.8 | 92 ml | 8 ml | 900 ml |
| 5.9 | 90 ml | 10 ml | 900 ml |
| 6.0 | 87.7 ml | 12.3 ml | 900 ml |
| 6.1 | 85 ml | 15 ml | 900 ml |
| 6.2 | 81.5 ml | 18.5 ml | 900 ml |
| 6.3 | 77.5 ml | 22.5 ml | 900 ml |
| 6.4 | 73.5 ml | 26.5 ml | 900 ml |
| 6.5 | 68.5 ml | 31.5 ml | 900 ml |
| 6.6 | 62.5 ml | 37.5 ml | 900 ml |
| 6.7 | 56.5 ml | 43.5 ml | 900 ml |
| 6.8 | 51 ml | 49 ml | 900 ml |
| 6.9 | 45 ml | 55 ml | 900 ml |
| 7.0 | 39 ml | 61 ml | 900 ml |
| 7.1 | 33 ml | 67 ml | 900 ml |
| 7.2 * | 28 ml | 72 ml | 900 ml |
| 7.3 | 23 ml | 77 ml | 900 ml |
| 7.4 | 19 ml | 81 ml | 900 ml |
| 7.5 | 16 ml | 84 ml | 900 ml |
| 7.6 | 13 ml | 87 ml | 900 ml |
| 7.7 | 10.5 ml | 89.5 ml | 900 ml |
| 7.8 | 8.5 ml | 91.5 ml | 900 ml |
| 7.9 | 6.7 ml | 93.3 ml | 900 ml |
| 8.0 | 5.3 ml | 94.7 ml | 900 ml |
| * To prepare 1000 ml solution of 1M Sodium phosphate buffer of pH 7.2, mix 28 ml of 1M Sodium phosphate monobasic, 72 ml of Sodium Phosphate dibasic and 900 ml of water. | |||
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