Description
The Sorensen phosphate buffer is also known as mixed sodium salts with phosphate. The osmolarity of a 0.1 M solution at pH 7.2 is 226 milliosmoles; with the addition of 0.18 M sucrose to the solution, the osmolarity rises to 425 milliosmoles. The pH can be specified when ordering. The maximum storage duration after receipt is 3 months.
All used products are chosen for their purity.
Storage: 4-8°C.
INFO PLUS:
Phosphate buffer (Sorensen buffer) pH 5.8-8.
Advantages:
The most physiological among common buffers. Mimics certain components of extracellular fluids.
Non-toxic to cells.
pH variation is minimal with temperature changes.
Stable for several weeks at 4°C.
Disadvantages:
Precipitation is more likely to occur during fixation. Tends to form precipitates in the presence of calcium ions. Precipitates uranium acetate and tends to react with lead salts.
Slowly becomes contaminated by microorganisms.
Mother solutions:
Sodium dibasic phosphate 0.2 M 1 liter.
Na2HPO4 * 2H20 (MW = 178.05) 35.61 g
or
Na2HPO4 * 7H20 (MW = 268.07) 53.65 g
or
Na2HPO4 * 12H20 (MW = 358.14) 71.64 g
ddH20 to make 1 liter.
Sodium monobasic phosphate 0.2 M 1 liter.
NaH2PO4 * H20 (MW = 138.01) 27.6 g
or
NaH2PO4 * 2H20 (MW = 156.03) 31.21 g
ddH20 to make 1 liter.
Working buffer: 0.1 M 100 ml.
Mix X ml of 0.2 M sodium dibasic phosphate with Y ml of 0.2 M sodium monobasic phosphate. Dilute to 100 ml with ddH20 or dilute 1:1 with a fixative.
pH (25°C) X ml Y ml
pH 7.0 X ml 30.5 ml Y ml 19.5 ml
7.2 36.0 ml 14.0 ml
7.4 40.5 ml 9.5 ml
7.6 43.5 ml 6.5 ml
7.8 45.75 ml 4.25 ml
8.0 47.35 ml 2.65 ml
Osmolarity is adjusted by varying the molarity of phosphates or by adding sucrose, glucose, or sodium chloride.
At pH 7.2:
0.10 M = 226 mOs (milliosmoles)
0.05 M = 118 mOs
0.075 M = 180 mOs
0.15 M = 350 mOs
Osmolarity is adjusted by varying the molarity of phosphates or by adding sucrose, glucose, or sodium chloride.
