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
0°	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