Problem Possible cause Solution
Sample properties cause slow
stabilization or inaccurate
measurements.
The sample absorbs carbon
dioxide (CO
2
) from the air,
which causes the pH value to
slowly decrease in low ionic
strength (LIS) or high purity
samples.
Use the LIS chamber for
LIS/high purity samples to
prevent CO
2
absorption.
The sample temperature is
low, or there is a large
temperature difference
between samples.
Increase the sample temperature
or adjust the temperature of
different samples to be the same
(within 2 °C (3.6 °F)).
Procedure problem causes
slow stabilization and prevents
accurate calibrations or
measurements.
The probe is not conditioned
to the sample.
Soak the probe in the sample
before sample measurements.
Refer to Preparation for use
on page 5.
Air bubbles are around or
below the probe tip.
Carefully tap or shake the probe
to remove air bubbles.
The electrical connection
through the reference junction
is not sufficient.
Shake the probe in the solution
from side to side to refresh the
reference junction.
The stir speed is too slow or
too fast.
Try a different stir speed.
An incorrect buffer solution
was used or the buffer solution
has contamination.
Use the specified buffer solutions
of good quality.
Section 10 Consumables
Note: Product and Article numbers may vary for some selling regions. Contact the appropriate distributor or refer to
the company website for contact information.
Description Quantity Item no.
Hach pH electrode storage solution 500 mL 2756549
Electrode cleaning solution for regular maintenance 500 mL 2965249
Electrode cleaning solution for minerals/inorganic
contamination
500 mL 2975149
Electrode cleaning solution for proteins/organic
contamination
250 mL C20C370
Electrode cleaning solution for fats, oils and grease
contamination
500 mL 2964449
Electrode cleaning solution, extra strong 250 mL S16M002
10.1 Recommended standards
Description Unit Item no.
pH 4.01 buffer solution, Singlet one-use packets, 20 mL each 20/pkg 2770020
pH 7.00 buffer solution, Singlet one-use packets, 20 mL each 20/pkg 2770120
14 English
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