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Potassium phosphate dibasic and monobasic

Catalog Number: 151945, 151946, 191430, 191431, 191432, 194727, 194845, 194846, 195453
Potassium phosphate dibasic and monobasic


Structure:

Monobasic
Dibasic
Dibasic, anhydrousDibasic, trihydrateMonobasic, anhydrous
Molecular Formula:K2HPO4K2HPO4·3H2OKH2PO4
Molecular Weight:174.18228.2136.09
CAS #7758-11-416788-57-17778-77-0

Physical Description: White crystalline to granular powder; somewhat hygroscopic.

Synonyms:


Solubility: Soluble in water; Insoluble to slightly soluble in ethanol; insoluble in alcohol

Description: Potassium phosphate is a reagent with high buffering capacity. It occurs in several forms: monobasic, dibasic, and tribasic (K3PO4). Most pH neutral potassium phosphate buffer solutions consist of mixtures of the monobasic and dibasic forms to varying degrees, depending on the desired pH.

Typically used as a component for a wide variety of media used in the culture of microorganisms, as a component in phosphate buffered saline (PBS). In addition to helping maintain pH, it supplies essential phosphate.

Typical Buffer Preparation/Formulations:

Prepare the following solutions:

Formulation Guide:

1 Liter of 0.05 M Phosphate Buffer (25°C)
1 Liter of 0.05 M Phosphate Buffer with 0.15 M NaCl (25°C)
Desired pH
1 M Monobasic Solution
1 M Dibasic Solution
1 M Monobasic Solution
1 M Dibasic Solution
5 M Sodium Chloride Solution
6.6
32.0 ml
18.0 ml
26.6 ml
23.4 ml
30.0 ml
6.7
29.8 ml
20.2 ml
23.7 ml
26.3 ml
30.0 ml
6.8
26.5 ml
23.5 ml
20.9 ml
29.1 ml
30.0 ml
6.9
24.0 ml
26.0 ml
18.1 ml
31.9 ml
30.0 ml
7.0
21.1 ml
28.9 ml
15.6 ml
34.4 ml
30.0 ml
7.1
18.4 ml
31.6 ml
13.2 ml
36.8 ml
30.0 ml
7.2
16.8 ml
34.2 ml
11.1 ml
38.9 ml
30.0 ml
7.3
13.4 ml
36.6 ml
9.2 ml
40.8 ml
30.0 ml
7.4
11.2 ml
38.8 ml
7.6 ml
42.4 ml
30.0 ml
7.5
9.4 ml
40.6 ml
6.3 ml
43.7 ml
30.0 ml
7.6
7.8 ml
42.2 ml
5.1 ml
44.9 ml
30.0 ml

Add the specified amount to a volumetric flask and QS to 1 liter with distilled, deionized water.

The ratios above are specific for 50 mM buffers at the designated pH. Higher concentrations of phosphate or the presence of neutral salts will alter the pH. The volumes indicated on the right side of the table can be used as a guide in the preparation of 50 mM phosphate buffered saline (PBS). Sodium chloride lowers the pH approximately 0.01 pH unit for each 0.01 increase in molarity.4

For phosphate buffers, the pH increases with decreasing temperature. Compared with a buffer at 25°C, buffers at 4°C will be 0.08 pH unit higher and a buffer at 37°C will be 0.025 pH unit lower. The concentration of phosphate also influences pH. The dilution value for phosphate, defined as the change of pH of a buffer when diluted with an equivalent volume of water is 0.08.5 Therefore, a 25 mM phosphate buffer prepared with half of the volumes indicated on the above table for a specific pH, would be approximately 0.08 pH units higher than the expected pH. Likewise, a 100 mM buffer prepared with double the volumes indicated would result in a pH approximately 0.08 pH units lower.

The pH values listed are only approximate. The pH should be measured prior to use and adjusted, if necessary.

Typical Phosphate Buffered Saline Formulations:

with calcium and magnesium:
Component
mg/lt
Mol. (mM)
Inorganic Salts
Calcium Chloride [CaCl2 2H2O] Dihydrate
132.50000
0.90
Magnesium Chloride [MgCl2 6H2O] Hexahydrate
100.00000
0.49
Potassium Chloride [KCl]
200.00000
2.68
Potassium Phosphate Monobasic [KH2PO4]
200.00000
1.47
Sodium Chloride [NaCl]
8000.00000
136.89
Sodium Phosphate Dibasic [Na2HPO4]
1150.00000
8.10

without calcium and magnesium:
Componentsmg/literMol. (mM)
Inorganic Salts
Potassium Chloride [KCl]
200.00
2.68
Potassium Phosphate Monobasic [KH2PO4]
200.00
1.47
Sodium Chloride [NaCl]
8000.00
136.89
Sodium Phosphate Dibasic [Na2HPO4]
1150.00
8.10

Availability:

Catalog NumberDescriptionSize
151945Potassium phosphate dibasic, anhydrous100 g
500 g
1 kg
5 kg
151946Potassium phosphate dibasic, trihydrate100 g
500 g
1 kg
10 kg
194845Potassium phosphate dibasic, trihydrate, molecular biology reagent100 g
500 g
1 kg
191431Potassium phosphate dibasic, anhydrous, ACS Reagent Grade100 g
500 g
1 kg
5 kg
191432Potassium phosphate dibasic, trihydrate, reagent grade100 g
500 g
1 kg
5 kg
194727Potassium phosphate monobasic, anhydrous, cell culture reagent100 g
500 g
1 kg
195453Potassium phosphate monobasic, anhydrous100 g
500 g
1 kg
10 kg
194846Potassium phosphate monobasic, anhydrous, molecular biology reagent100 g
500 g
1 kg
191430Potassium phosphate monobasic, anhydrous, ACS Reagent Grade100 g
500 g
1 kg
5 kg

Also Available:

Catalog NumberDescriptionSize
152575Sodium Chloride, ACS Reagent Grade500 g
1 kg
5 kg
10 kg
195088Calcium Chloride, Dihydrate500 g
1 kg
5 kg
191421Magnesium Chloride, Hexahydrate, ACS Reagent Grade100 g
500 g
1 kg
5 kg
191427Potassium Chloride, ACS Reagent Grade100 g
500 g
1 kg
5 kg
191440Sodium phosphate dibasic, anhydrous, ACS Reagent Grade100 g
500 g
1 kg
5 kg

References:
  1. Merck Index, 12th Ed., No. 7828 (dibasic)
  2. Merck Index, 12th Ed., No. 7829 (monobasic)
  3. Molecular Cloning: A Laboratory Manual, 3rd Ed., Sambrook, J.F., et al. (eds.), Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, p. A1.5 (2001).
  4. Bates, R.G., Determination of pH - theory and practice, Wiley and Sons, New York (1964).
  5. Bates, R.G., "Revised Standard Values for pH Measurements from 0-95" C.J. Res. Nat. Bur. Stds. 66A, 179-184 (1962).
  6. Dawson, R.M.C., et al. (eds.), Data for Biochemical Research, Oxford, p. 421 (1986).
  7. Enfors, S.O., et al., "Combined use of extraction and genetic engineering for protein purification: recovery of beta-galactosidase fused proteins." Bioseparation, v. 1(3-4), 305-310 (1990).
  8. Green, A.A. and Hughes, W.L., "Protein fractionation on the basis of solubility in aqueous solutions of salts and organic solvents." Meth. Enzymol., v. 1, 67-90 (1955).
  9. Pardue, K., and Williams, D., "Quantitative determination of non-ionic surfactants in protein samples, using ion-exchange guard columns." Biotechniques, v. 14(4), 580-583 (1993).
  10. Pikal-Cleland, K.A., et al., "Protein denaturation during freezing and thawing in phosphate buffer systems: monobasic and tetrameric beta-galactosidase." Arch. Biochem. Biophys., v. 384(2), 398-406 (2000).
  11. Wheatley, J.B. and Schmidt, D.E. Jr., "Salt-induced immobilization of affinity ligands onto epoxide-activated supports." J. Chromatogr. A., v. 849(1), 1-12 (1999).