Sorensen developed a phosphate buffer that covers the physiologic pH range.
Reagents and molecular weights:
(1) disodium acid phosphate (dibasic sodium phosphate): 142 g (anhydrous)
(2) monopotassium acid phosphate (monobasic potassium phosphate): 136.1 (anhydrous)
NOTE: Be sure the reagents are anhydrous.
Solutions: Dilute (0.067 M in Documenta Geigy, 0.1 M in Henry)
pH range: 5.288 to 8.043 at 20°C
|
pH |
mL disodium 0.1 M (14.2 g/L) |
mL monopotassium 0.1 M (13.6 g/L) |
|
5.288 |
2.5 |
97.5 |
|
5.589 |
5.0 |
95.0 |
|
5.906 |
10.0 |
90.0 |
|
6.239 |
20.0 |
80.0 |
|
6.468 |
30.0 |
70.0 |
|
6.643 |
40.0 |
60.0 |
|
6.813 |
50.0 |
50.0 |
|
6.979 |
60.0 |
40.0 |
|
7.168 |
70.0 |
30.0 |
|
7.381 |
80.0 |
20.0 |
|
7.731 |
90.0 |
10.0 |
|
8.043 |
95.0 |
5.0 |
volume of dibasic sodium phosphate in mL to make up 100 mL buffer over pH range 5.288 to 6.239 =
= (17.3068 * ((pH)^2)) – (181.3018 * (pH)) + 477.38115
volume of dibasic sodium phosphate in mL to make up 100 mL buffer over pH range 6.239 to 7.168 =
= (54.9885 * (pH)) – 324.4312
volume of dibasic sodium phosphate in mL to make up 100 mL buffer over pH range 7.168 to 8.043 =
= (-24.1206 * ((pH)^2)) + (395.13233 * (pH)) – 1522.798
To make up 100 mL of the buffer,
the volume of monobasic potassium phosphate in mL =
= 100 – (volume of dibasic sodium phosphate in mL)
Specialty: Clinical Laboratory
