Wednesday, July 15, 2009

Citrate Phosphate Buffer Recipe

Add the following to create 100 ml of phosphate/citrate buffer solution. Stock solutions are 0.2 M dibasic sodium phosphate; 0.1 M citric acid (Pearse, 1980).

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Hot relax said...

Very good info

rids said...

i would like to make 50mM of citrate phosphate buffer at pH 6 .. would you suggest how should i make tht. . .

Yogendra Singh and Anita Singh said...

Rids thanks for showing your interest in ligninblack, i request u 2 kindly join my site.
Your query: to make 50mM of citrate phosphate buffer at pH 6.

Answer:Use Monosodium phosphate, monohydrate= 0.6072% and
Disodium phosphate, heptahydrate= 0.1609 %
(for 1 lit pH 6)

or prepare stock solution of 100mM and dilute it to 50mM.

For 100 mM: Use Monosodium phosphate, monohydrate=1.214 % and
Disodium phosphate, heptahydrate= 0.0.3218 %
(for 1 lit for pH 6)

dc182 said...

Help me please to find out what is the original molarity of citrate phosphate buffer in case i made it by recipe described above?
For example what is the molarity of solution prepared by mixing 25.7ml of 0.2M Na2HPO4 and 24.3ml of 0.1M citric acid at pH 5.0? And how can i prepare this 10 mM McIlvaine buffer using only Na2HPO4 and citric acid?
Thanks a lot!)

Yogendra and Anita Singh said...

Hi dc182, sorry for the late reply, I think this formula can solve your quarry.

Total Molarity (Mt) ={ (M1 X V1) + (M2 X V2)}/V1 + V2

Example of the combined solutions formula:

250. mL of 1.00 M NaCl solution and 425 mL of a 0.750 M NaCl solution are mixed together. What
is the molarity of the combined solution?

{(0.250 L X 1.00 M) + (0.425 L X 0.750 M) }/ 0.250 L + 0.425 L = 0.843 M NaCl

pat said...

hello! how would you make 50 mM citrate phosphate buffer at pH 5?

James Blanchard said...

In all cases I have seen the McIlwaine's buffer consists of mixing 0.2M Na2HPO4 and 0.1M Citric acid solutions in various ratios. My question about his buffer and buffers in general is: Can Na2HPO4 be replace by K2HPO4 in this buffer? In general why can't sodium and potassium salts be interchanged? or can they? What would be a downside of this if any? Thank you.