Measuring Hints
• Pipet 50 mL of TISAB II per 50 mL standard or sample,
or 10 mL of TISAB III per 90 mL standard or sample.
• Stir all standards and samples at a uniform rate during
measurement. Magnetic stirrers may generate sufficient heat
to change solution temperature. Place a piece of insulating
material such as cork, cardboard, or styrofoam between the
stirrer and beaker.
• Verify calibration every two hours by placing electrodes in a
fresh aliquot of the first standard solution used for
calibration. If the value has changed, recalibrate.
• Always use fresh standards for calibration.
• Always rinse electrodes with deionized water between
measurements (see
Electrode Preparation
). Shake after
rinsing to prevent solution carry-over.
Do not wipe or rub
the sensing element.
• Allow all standards and samples to come to the same
temperature for precise measurement.
• After immersion in solution, check electrode for any air
bubbles on element surface and remove by redipping
electrode into solution.
• For high ionic strength samples, prepare standards with
composition similar to that of sample.
• Highly acidic or highly basic solutions should be adjusted to
pH 5-6 before addition of TISAB.
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