Thermo Fisher Scientific CyberScan pH 1100/pH 2100 - Manual (Page 57)

Instruction Manual pH 1100/ 2100
57
13 ADDITIONAL INFORMATION
13.1 pH and Temperature
The pH electrode is affected by temperature changes. Automatic Temperature Compensation (ATC) compensates for
these temperature changes. Some solutions show an increase while others a decrease in pH with the same temperature
change. Record the solution temperature along with the pH value, or the measurement may be meaningless.
Temperature changes also affect the signal the pH electrode sends to the meter and causes a loss of accuracy for the
reading. To limit the loss of accuracy during calibration, make the temperature of the pH buffer calibrating solutions and
the sample solution the same.
13.2 pH Buffer Calibration Solution
You can use standard buffer solutions to calibrate a pH meter before you measure the pH of a sample. Calibration
solutions serve as basis of comparison between measurements. The most common standard buffers are pH 4.01,
pH 7.00 and pH 10.01.
For 1-point calibration, use a standard buffer of pH 7.00 or 6.86, or a standard or custom buffer whose pH value is close
to that of the sample. Use 2-point calibration when you know the sample is acidic (low pH) or basic (high pH). For
example: in acidic samples, use standard buffers such as pH 7.00 and pH 4.01; in basic samples, use standards such as
pH 7.00 and pH 10.01.
Use multi-point calibration when the sample pH is completely unknown or for best accuracy over the entire pH range.
Contact your distributor for information on pH buffer and calibration solutions.
13.3 Standard pH Buffers
The following table shows the various pH values at different temperature of the solution during calibration. The table also
illustrates why a calibration value may be different from the buffer value at 25°C.
USA Buffer NIST Buffer
Temperature (°C)
1.68 4.01 7.00 10.01 12.45 1.68 4.01 6.86 9.18 12.45
0 1.67 4.01 7.12 10.32 13.43 1.67 4.01 6.98 9.46 13.43
5 1.67 4.01 7.09 10.25 13.21 1.67 4.01 6.95 9.40 13.21
10 1.67 4.01 7.06 10.18 13.00 1.67 4.01 6.92 9.33 13.00
15 1.67 4.00 7.04 10.12 12.81 1.67 4.00 6.90 9.28 12.81
20 1.68 4.00 7.02 10.06 12.63 1.68 4.00 6.87 9.23 12.63
25 1.68 4.01 7.00 10.01 12.45 1.68 4.01 6.86 9.18 12.45
30 1.69 4.01 6.99 9.97 12.29 1.69 4.01 6.85 9.14 12.29
35 1.69 4.02 6.98 9.93 12.13 1.69 4.02 6.84 9.11 12.13
40 1.70 4.03 6.97 9.93 11.99 1.70 4.03 6.84 9.07 11.99
45 1.70 4.04 6.97 9.86 11.84 1.70 4.04 6.83 9.04 11.84
50 1.71 4.06 6.97 9.83 11.70 1.71 4.06 6.83 9.01 11.70
55 1.72 4.08 6.97 9.81 11.58 1.72 4.08 6.83 8.99 11.58
60 1.73 4.10 6.98 9.79 11.45 1.73 4.10 6.84 8.96 11.45
65 1.73 4.11 6.98 9.77 11.45 1.73 4.11 6.84 8.94 11.45
70 1.74 4.12 6.99 9.76 11.45 1.74 4.12 6.84 8.92 11.45
75 1.75 4.14 6.99 9.75 11.45 1.75 4.14 6.85 8.91 11.45
80 1.77 4.16 7.00 9.74 11.45 1.77 4.16 6.86 8.89 11.45
85 1.78 4.18 7.01 9.73 11.45 1.78 4.18 6.87 8.87 11.45
90 1.80 4.23 7.02 9.73 11.45 1.80 4.23 6.88 8.85 11.45
95 1.81 4.23 7.03 9.74 11.45 1.81 4.23 6.88 8.85 11.45
100 1.81 4.23 7.03 9.74 11.45 1.81 4.23 6.88 8.85 11.45
105 1.81 4.23 7.03 9.74 11.45 1.81 4.23 6.88 8.85 11.45