Paul.xu at 19:17, 20 May 2019

2019-05-20T19:17:02Z

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'''1 M K-Phosphate, pH 7.0'''

300 ml of 1 M KH2PO4, 700 ml 1M K2HPO4, the pH is 7.0 measured using a pH meter.

'''Stock solution A'''

2 M monobasic sodium phosphate, monohydrate (276 g/L), NaH2PO4

'''Stock solution B'''

2 M dibasic sodium phosphate (284 g/L). Na2HPO4

Filter thru 0.45 u filter

Make 0.2 M: Dilute 10 times. (100 ml  +  900 ml water), filter thru 0.45 u filter

Mixing an appropriate volume ('''ml''') of'''  A''' and'''  B''' as shown in the table below and diluting to a total volume of 200 ml, to make a 0.1 M phosphate buffer of the required pH at room temperature.

{| border="1"
|-
| <center>0.2 M NaH2PO4</center>
| <center>0.2 M Na2HPO4</center>
| pH
|-
| 92.0
| 8.0
| 5.8
|-
| 90.0
| 10.0
| 5.9
|-
| 87.7
| 12.3
| 6.0
|-
| 85.5
| 15.0
| 6.1
|-
| 81.5
| 19.5
| 6.2
|-
| 77.5
| 22.5
| 6.3
|-
| 73.5
| 26.5
| 6.4
|-
| 68.5
| 31.5
| 6.5
|-
| 62.5
| 37.5
| 6.6
|-
| 56.5
| 43.5
| 6.7
|-
| 51.0
| 49.0
| 6.8
|-
| 45.0
| 55.0
| 6.9
|-
| 39.0
| 61.0
| 7.0
|-
| 33.0
| 67.0
| 7.1
|-
| 28.0
| 72.0
| 7.2
|-
| 23.0
| 77.0
| 7.3
|-
| '''19.0'''
| '''81.0'''
| '''7.4'''
|-
| 16.0
| 84.0
| 7.5
|-
| 13.0
| 87.0
| 7.6
|-
| 10.5
| 89.5
| 7.7
|-
| 8.5
| 91.5
| 7.8
|-
| 7.0
| 93
| 7.9
|-
| 5.3
| 94.7
| 8.0
|}

== Potassium Phosphate Monobasic Anhydrous--Sodium Phosphate Dibasic Heptahydrate ==

{| cellspacing="1" cellpadding="2" border="1" bgcolor="#006699"
|-
| width="139" align="center" | Potassium 
Phosphate Monobasic Anhydrous,  '''KH2PO4''', g/L

| width="132" align="center" | Sodium
Phosphate Dibasic Heptahydrate, '''Na2HPO4·7H2O''' g/L

| width="29" align="center" | '''23 °C pH'''
| width="5" align="center" bgcolor="#ffffff" |  
| width="139" align="center" | Potassium Phosphate Monobasic Anhydrous, KH2PO4, g/L 
| width="132" align="center" | Sodium Phosphate
Dibasic Heptahydrate Na2HPO4·7H2O, g/L

| width="29" valign="top" align="center" | '''23 °C pH'''
|- bgcolor="#f2f2f2"
| 22.4
| 3.49
| 5.7
| bgcolor="#ffffff" |  
| 10.80
| 29.51
| 6.9
|- bgcolor="#f2f2f2"
| 22.08
| 4.29
| 5.8
| bgcolor="#ffffff" |  
| 9.36
| 32.73
| 7.0
|- bgcolor="#f2f2f2"
| 21.60
| 5.37
| 5.9
| bgcolor="#ffffff" |  
| 7.92
| 35.95
| 7.1
|- bgcolor="#f2f2f2"
| 21.05
| 6.60
| 6.0
| bgcolor="#ffffff" |  
| 6.72
| 38.63
| 7.2
|- bgcolor="#f2f2f2"
| 20.40
| 8.05
| 6.1
| bgcolor="#ffffff" |  
| 5.52
| 41.31
| 7.3
|- bgcolor="#f2f2f2"
| 19.56
| 9.93
| 6.2
| bgcolor="#ffffff" |  
| 4.56
| 43.46
| 7.4
|- bgcolor="#f2f2f2"
| 18.60
| 12.07
| 6.3
| bgcolor="#ffffff" |  
| 3.84
| 45.07
| 7.5
|- bgcolor="#f2f2f2"
| 17.64
| 14.22
| 6.4
| bgcolor="#ffffff" |  
| 3.12
| 46.68
| 7.6
|- bgcolor="#f2f2f2"
| 16.44
| 16.90
| 6.5
| bgcolor="#ffffff" |  
| 2.52
| 48.55
| 7.7
|- bgcolor="#f2f2f2"
| 15.00
| 20.12
| 6.6
| bgcolor="#ffffff" |  
| 2.04
| 49.09
| 7.8
|- bgcolor="#f2f2f2"
| 13.56
| 23.34
| 6.7
| bgcolor="#ffffff" |  
| 1.68
| 49.89
| 7.9
|- bgcolor="#f2f2f2"
| 12.24
| 26.29
| 6.8
| bgcolor="#ffffff" |  
| 1.27
| 50.81
| 8.0
|}

== Na2HPO4 – NaH2PO4 Buffer Solutions, pH 5.8–8.0 at 25 °C1 ==

 Na2HPO4 • 2H2O, M. wt. 178.05; 0.2M-solution contains 35.61 g/l. Na2HPO4 • 12H2O, M. wt. 358.22; 0.2M -solution contains 71.64 g/l. NaH2PO4 • H2O, M. wt. 138.01;  0.2M-solution contains 27.6 g/l. NaH2PO4 • 2H2O, M. wt. 156.03; 0.2M-solution contains 31.21 g/l. x ml 0.2M-Na2HPO4, y ml 0.2M-NaH2PO4; diluted to 100 ml with H2O.

{| bgcolor="#006699" width="345" cellspacing="1" cellpadding="2" border="1"
|-
| pH, 25 °C
| align="center" width="135" class="one" | x ml 0.2M-Na2HPO4
| align="center" width="160" class="one" | y ml 0.2M-NaH2PO2
|-
| 5.8
| 4.0
| 46.0
|-
| 6.0
| 6.15
| 43.85
|-
| 6.2
| 9.25
| 40.75
|-
| 6.4
| 13.25
| 36.75
|-
| 6.6
| 18.75
| 31.25
|-
| 6.8
| 24.5
| 25.5
|-
| 7.0
| 30.5
| 19.5
|-
| 7.2
| 36.0
| 14.0
|-
| 7.4
| 40.5
| 9.5
|-
| 7.6
| 43.5
| 6.5
|-
| 7.8
| 45.75
| 4.25
|-
| 8.0
| 47.35
| 2.65
|}

== Yet Another Protocol 1 M sodium phosphate buffer (pH 6.0-7.2) ==

Mixing 1 M NaH2PO4 (monobasic) and 1 M Na2HPO4 (dibasic) stock solutions in the volumes designated in the table below results in 1 L of 1 M sodium phosphate buffer of the desired pH.

To prepare the stock solutions:

Dissolve 138 g of Na2HPO4•H2O (monobasic; m.w. = 138 g) in sufficient H2O to make a final volume of 1 L

Dissolve 142 g of Na2HPO4 (dibasic; m.w. = 142 g) in sufficient H2O to make a final volume of 1 L.

{|
|-
| align="left" height="16" | pH
| align="left" | Volume (mL) of 1 M Na2HPO4
| align="left" | Volume (mL) of 1 M NaH2PO4
|-
| align="right" height="16" | 5.8
| align="right" | 7.9
| align="right" | 92.1
|-
| align="right" height="16" | 6
| align="right" | 12
| align="right" | 88
|-
| align="right" height="16" | 6.2
| align="right" | 17.8
| align="right" | 88.2
|-
| align="right" height="16" | 6.4
| align="right" | 25.5
| align="right" | 74.5
|-
| align="right" height="16" | 6.6
| align="right" | 35.2
| align="right" | 64.8
|-
| align="right" height="16" | 6.8
| align="right" | 46.3
| align="right" | 53.7
|-
| align="right" height="16" | 7
| align="right" | 57.7
| align="right" | 42.3
|-
| align="right" height="16" | 7.2
| align="right" | 68.4
| align="right" | 31.6
|-
| align="right" height="16" | 7.4
| align="right" | 77.4
| align="right" | 22.6
|-
| align="right" height="16" | 7.6
| align="right" | 84.5
| align="right" | 15.5
|-
| align="right" height="16" | 7.8
| align="right" | 89.6
| align="right" | 10.4
|-
| align="right" height="16" | 8
| align="right" | 93.2
| align="right" | 6.8
|}

0.1 M sodium phosphate buffer (pH 7.4)

Add 3.1 g of NaH2PO4•H2O and 10.9 g of Na2HPO4 (anhydrous) to distilled H2O to make a volume of 1 L. The pH of the final solution will be 7.4. This buffer can be stored for up to 1 mo at 4°C.

0.1 M sodium phosphate buffer (from 1 M stocks) at 25°C

To prepare 1 L of 0.1 M sodium phosphate buffer of the desired pH, the following mixtures should be diluted to 1 L (final volume) with H2O.

{|
|-
| align="left" height="16" | pH
| align="left" | Volume (mL) of 1 M Na2HPO4
| align="left" | Volume (mL) of 1 M NaH2PO4
|-
| align="right" height="16" | 5.8
| align="right" | 7.9
| align="right" | 92.1
|-
| align="right" height="16" | 6
| align="right" | 12
| align="right" | 88
|-
| align="right" height="16" | 6.2
| align="right" | 17.8
| align="right" | 88.2
|-
| align="right" height="16" | 6.4
| align="right" | 25.5
| align="right" | 74.5
|-
| align="right" height="16" | 6.6
| align="right" | 35.2
| align="right" | 64.8
|-
| align="right" height="16" | 6.8
| align="right" | 46.3
| align="right" | 53.7
|-
| align="right" height="16" | 7
| align="right" | 57.7
| align="right" | 42.3
|-
| align="right" height="16" | 7.2
| align="right" | 68.4
| align="right" | 31.6
|-
| align="right" height="16" | 7.4
| align="right" | 77.4
| align="right" | 22.6
|-
| align="right" height="16" | 7.6
| align="right" | 84.5
| align="right" | 15.5
|-
| align="right" height="16" | 7.8
| align="right" | 89.6
| align="right" | 10.4
|-
| align="right" height="16" | 8
| align="right" | 93.2
| align="right" | 6.8
|}

{| border="1" cellspacing="1" cellpadding="1" style="width:500px;"
|-
| 0.2 M KH2PO4
| 0.2 M K2HPO4
| (to 200ml) pH
|-
| 91.5
| 8.5
| 5.8
|-
| 86.8
| 13.2
| 6.0
|-
| 80.8
| 19.2
| 6.2
|-
| 72.2
| 27.8
| 6.4
|-
| 61.9
| 38.1
| 6.6
|-
| 50.3
| 49.7
| 6.8
|-
| 38.5
| 61.5
| 7.0
|-
| 28.3
| 71.7
| 7.2
|-
| 19.8
| 80.2
| 7.4
|-
| 13.4
| 86.6
| 7.6
|-
| 9.2
| 90.8
| 7.8
|-
| 6.0
| 94.0
| 8.0
|}

[[Category:Buffer Recipe]]

Phosphate Buffer Chart - Revision history

Paul.xu at 19:17, 20 May 2019