Hach POCKET COLORIMETER II, Instruction Manuals

Page: 74 / 116

1—74
pH,
continued
Accuracy Check
Preparation of pH 7.0 Standard Solution
A pH 7.00 standard solution is necessary to calibrate or check the accuracy of the pH
measurement using the Standard Calibration Adjust feature (see
Standard Calibration
Adjust on page 2—13 ). Use the pH 7.00 Buffer Vial (included in this kit) or bulk buffer
solution (see Optional Reagents on page 1—76 ). Add 0.5 mL of Phenol Red Solution to
10 mL of pH 7.00 Buffer Solution to prepare the color standard. Do not use colored
buffer solutions.
For greatest accuracy, adjust the calibration curve using Standard Calibration Adjust
with each new lot of Phenol Red Indicator. Periodically check the strength of the
indicator by testing a pH 7.0 Buffer Solution.
Method Performance
Typical Precision (95% CI):
7.0 ± 0.1 pH