Phosphate buffer

Purpose

Phosphate buffer is a multi-purpose buffer used for many molecular biology procedures.

How to make phosphate buffer

Source: Sörensen; in Hayat, 1986.

0.2 M monobasic stock

• 15.6 g sodium phosphate monobasic dihydrate (NaH₂PO₄·2H₂O, MW 155.99 g/mol), or 13.9 g of the anhydrous form
• 500 mL dH₂O

0.2 M dibasic stock

• 53.65 g sodium phosphate dibasic heptahydrate (Na₂HPO₄·7H₂O, MW 268.07 g/mol), or 28.4 g of the anhydrous form
• 1 L dH₂O

0.1 M sodium phosphate buffer

To make 600mL 0.1 M sodium phosphate buffer, combine the following quantities of each stock and add dH₂O to bring up to 600 mL:

monobasic (mL)	dibasic (mL)	pH
280.5	19.5	5.7
276	24	5.8
270	30	5.9
263.1	36.9	6.0
255	45	6.1
244.5	55.5	6.2
232.5	67.5	6.3
220.5	79.5	6.4
205.5	94.5	6.5
187.5	112.5	6.6
169.5	130.5	6.7
153	147	6.8
135	165	6.9
117	183	7.0
99	201	7.1
84	216	7.2
69	231	7.3
57	243	7.4
48	252	7.5
39	261	7.6
31.5	271.5	7.7
25.5	274.5	7.8
21	279	7.9
15.9	284.1	8.0

Safety

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References

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