Appendix; Frequently Asked Questions - Horiba Scientific LAQUAtwin B-74 Series Manual

8

Appendix

8.1

Frequently asked questions

Question
How long is the
sensor's service
life?
How can I check the
sensor's condition?
What shall I do if
two-point calibration
is failed?
What factors
interfere
measurement?
How can I eliminate
or reduce the mea-
surement
interference?
Are there any helpful
tips or precautions
to be aware for
measurement?
It depends on measurement samples and conditions.
It should be approx. 1500 measurements for typical samples.
Note that sensor deterioration and failure are not included in
the warranty.
Perform two-point calibration. If calibration error occurs, the
sensor is deteriorated. Replace the sensor.
Dirt in the response membrane and liquid junction is the main
cause of calibration failure. Clean the sensor thoroughly with
water, then gently wipe off the response membrane with soft
cloth or paper. If calibration is still failed after this, replace the
sensor.
Strong acids and strong alkalis influence measurement results.
Measure within the range from 4 pH to 12 pH.
-
Chloride ions (Cl
results. Therefore, a sample of seashore soil or fatty crop may
cause measurement errors. Also, a sample of significantly high
conductivity may cause measurement errors.
Refer to page 32 for details.
Diluting the sample to a concentration within the measurable
range can sometimes reduce measurement interference.
An ion chromatography precolumn (e.g. OnGuard II Ag
precolumn manufactured by Thermo Fisher Scientific Inc.) is
helpful to remove Chloride ions (Cl
Use the light shield cover to avoid direct sunlight during
measurement because the sensor is affected by light.
If the light shield cover is unavailable, for example, when a
sampling sheet holder cover is attached, shield the flat sensor
from light with an alternative.
When the sample amount is enough, washing the sensor twice
or so with the sample allows more accurate measurement.
Residue between the light shield cover and flat sensor pre-
vents accurate measurement. Before measurement of the next
sample, clean the sensor with tap water and remove moisture.
Answer
), oils, and fats influence measurement
28
-
).