Tips for pH Buffer Use

Tips for pH Buffer Use

These solutions of known pH value allow the user to adjust the system to read accurate measurements.

For best accuracy:

  • Standardization should be performed with fresh buffer solutions.
  • Buffers used should frame the range of pH for the samples being tested.
  • Buffers should be at the same temperature as the samples. (For example; if all your samples are at 50°C, warm your buffers to 50°C using a beaker in a water bath.)
  • Buffer values are dependent upon temperature. The following table lists the NIST values of pH buffers at various temperatures.

Table of NIST Values of pH Buffers
at Various Temperatures
Temperature
(°C)
4.01 Buffer 6.86 Buffer 9.18 Buffer
0.05M Potassium
Acid Phithalate
0.025M KH2PO4
0.025M Na2HPO4
0.01M Borax
4.00 pH 6.98 pH 9.46 pH
10° 4.00 pH 6.92 pH 9.33 pH
20° 4.00 pH 6.88 pH 9.22 pH
25° 4.01 pH 6.86 pH 9.18 pH
30° 4.02 pH 6.85 pH 9.14 pH
40° 4.04 pH 6.84 pH 9.07 pH
50° 4.06 pH 6.83 pH 9.01 pH
60° 4.09 pH 6.84 pH 8.96 pH
70° 4.13 pH 6.85 pH 8.92 pH
80° 4.16 pH 6.86 pH 8.88 pH
90° 4.21 pH 6.88 pH 8.85 pH