Tris HCl and phosphate buffers are useful at physiological pH. 

https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/General_Information/phospholipase_a2_colorimetric.pdf

Dear Nagarjuna,

The following text covers the answer to your question:

http://www4.mpbio.com/ecom/docs/proddata.nsf/5f64ffd4f38c2fda8525645d00769d68/d129d700747af023852568b200619fff

Cell Culture -- Biological Buffers and pH Control

All media used in tissue culture have as a basis as synthetic mixture of inorganic salts known as a "physiological" or balanced salt solution. The functions of this salt solution in the medium are to maintain proper pH, maintain ideal osmotic pressure, and provide a source of energy. The growth of animal cells in a nutritionally complete tissue culture medium is usually optimal when the medium is buffered at a pH in the range of 7.2-7.4. To function most effectively, the pKa of the chosen buffer should be as close as possible to the required pH.

The most commonly used buffer in tissue culture media is sodium bicarbonate. However, this buffer has two important disadvantages. First, the pKa of sodium bicarbonate is 6.3 at 37°C which results in suboptimal buffering throughout the physiological pH range. Second, carbon dioxide is released in the atmosphere with a resulting increase in alkalinity, and the number of hydroxyl ions produced increases according to the amount of sodium bicarbonate added to the medium. It is possible to control this by artificially supplying carbon dioxide to the atmosphere and preventing the gas from leaving the liquid, thereby reducing the hydroxyl ion concentration in solution.

Balanced salt solutions can be divided into two types: those intended to equilibrate with air in a closed system at a low concentration of sodium bicarbonate (Hanks' Balanced Salt Solution) and those intended to equilibrate with a gaseous phase containing approximately 5% CO2 at a higher concentration of sodium bicarbonate (Earle's Balanced Salt Solution). Earle's Balanced Salt Solution is a much better solution because it contains a greater amount of sodium bicarbonate, but it is more difficult to use since it requires a special gaseous mixture of 5% CO2 with 95% air to be provided by the culture medium. If this procedure is not carried out, the pH increases rapidly at normal incubation temperatures. The purple color of the medium indicates that the pH has risen, and cell growth is inhibited.

An alternative method is to use a medium which produces sufficient buffering capacity but does not require 5% CO2. In some cases, this can be achieved by using a medium containing Earle's salts but having the concentration of sodium bicarbonate reduced to 0.85 g/liter. An entirely different approach was devised by Leibovitz (1963). He utilized the buffering capacity of free base amino acids, omitted sodium bicarbonate, substituted galactose for glucose and added pyruvate. The pH of his L-15 medium is approximately 7.8 which is higher than that of most other media. Since there is no production of loss of CO2, the pH will not rise further. This medium makes possible the growth of cells in open culture vessels without regard to the CO2 content of the atmosphere.

Attempts have been made in recent years to find the most suitable buffer. The most commonly utilized alternative to bicarbonate is HEPES buffer which was first described by Good, et al. (1966). This acts as a zwitterion and has proved superior to conventional buffers in comparative biological assays with cell-free preparations. It has many properties which make it ideal as a buffer to tissue culture media, principally in that it does not require an enriched atmosphere to maintain the correct pH. HEPES does not bind divalent cations and is soluble to the extent of 2.25 M at 0°C. Note: since the DpKa/°C of -0.014, the pH reading recorded in a HEPES buffered medium will vary inversely with the temperature of the medium.

The following table expected pH levels at various temperatures:

Temperature °C

pH

Temperature °C

pH

5

7.58

23

7.47

15

7.56

24

7.46

16

7.55

25

7.44

17

7.54

26

7.43

18

7.53

27

7.42

19

7.52

28

7.41

20

7.5

29

7.4

21

7.44

30

7.38

22

7.48

37

7.3

HEPES is satisfactory as a buffer in tissue culture media for the growth of many different types of cells and viruses. It may exhibit toxicity at concentrations greater than 40 mM. Studies have indicated that 20 mM HEPES is the most satisfactory concentration of the buffer when both Hanks' and Earle's solutions are used. CO2 incubators should not be used with media buffered solely with HEPES. MP HEPES buffered liquid media are produced with a pH of 7.2-7.4 at 37°C. Powdered media are prepared so that a 1X solution will have a pH of 7.2-7.4 at 37°C without further adjustment.

Sodium bicarbonate should also be added as a nutritional requirement. It is recommended that the sodium bicarbonate concentration should not exceed 10 mM when the HEPES concentration is 20 mM. All single-strength (1X) liquid media contain either sodium bicarbonate or HEPES buffer or both. Ten times concentration (10X) liquid media do not contain buffer and powdered media are either buffer free or contain HEPES buffer only. Whenever sodium bicarbonate is used to buffer tissue culture media at a concentration of greater than 1.0 g/liter, a CO2 enriched atmosphere is required using a CO2 incubator.

Mammalian cells can survive over a wide pH range (6.6-7.8), but as a rule, the optimal growth of cells is obtained at pH 7.2-7.4. It is undesirable to allow the pH to deviate outside the limits of pH 6.8-7.6. It should be remembered that no buffer is capable of holding the pH constant in a system in which acids or bases are being produced. Buffers only slow the rate of pH change. Cells in culture produce acidic products which act to lower the pH of the medium.

Most of the media utilize phosphates and the bicarbonate system to buffer the media. The bicarbonate ion can be converted to gaseous carbon dioxide and lost from the medium resulting in a rise in the pH. Carbon dioxide can be maintained by supplying a special gas phase or by sealing the vessel tightly so that the CO2 produced by metabolic processes is retained in the vessel and re-absorbed by the medium.

Efforts to eliminate bicarbonate as a buffer system have been reported in medium SR1-8 and in medium L-15. Both media contain a phosphate buffer and increased amounts of amino acids to accomplish the buffering required.

A number of organic compounds have been described that have buffering capacity in the required range. HEPES will have a pronounced effect on the final pH. It is necessary to measure the pH at the temperature of use to determine the final pH due to the contribution by other buffers. HEPES buffer may be sterilized by steam and adjusted to desired pH with sodium hydroxide. Concentrations of 10-25 mM have been employed with no apparent toxicity. When utilizing HEPES, MP chooses a 20 or 25 mM concentration in the preparation of media unless it is otherwise specified. A mixture of acid form and base form of HEPES is used in combination in most of MP's media as this has been found to produce a more stable buffering system. Sodium chloride is reduced to keep the milliosmolality of the media containing both bicarbonate and HEPES in the range of non-HEPES containing media.

References:

Li, W. and Schlessinger, Mol. Cell Biol., v. 11, 375b-3761 (1991).

Mahaderan, L.C., et al., Cell, v. 65, 775-783 (1991).

Romeo, C., and Seed, B., Cell, v. 64, 1037-1046 (1991).

Evavold, B.D. and Allen, P.M., Science, v. 252, 1308-1310 (1991).

Conn, G., et al., Proc. Natl. Acad. Sci. USA, v. 87, 1323-1327 (1990).

Eugui, E.M. and Almquist, S.J., Proc. Natl. Acad. Sci. USA, v. 87, 1305-1309 (1990).

Hannigan, G.E. and Williams, B.R.G., Science, v. 251, 204-207 (1991).

Hyman, C., et al., Nature, v. 350, 230-232 (1991).

Just, U., et al., Cell, v. 64, 1163-1173 (1991).

Ten, H.-S, et al., Nature, v. 349, 241-243 (1991).

Faaland, C.A., et al., Mol. Cell. Bio., v. ii, 2697-2703 (1991).

Klemenz, R.K., et al., Mol. Cell. Bio., v. 11, 803-812 (1991).

Hoping this will be helpful,

Rafik

HEPES is the best for the cell culture but you can use also MOPS or bicarbonate buffers. Have a look to this article were they explain the buffering system:

http://cellgro.com/media/upload/file/techinfosheets/new/Buffering%20Systems.pdf

Noura S. Dosoky, the protocol that you suggested is nice but their is no references for that protocol and also what to measure is not specified i.e., whether assay is measuring the absorbance of lysolecithine  or a fatty acid

Bicarbonate buffer is another good alternative

I think you can use PBS as well. I use both and they work the same for me.