Hanna Instruments HI 88713 - Manual (Page 8)

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STARTUP STARTUP STARTUP STARTUP STARTUP
The HI 88713 Turbidity bench meter is supplied with all necessary accesories
Unpack the instrument and place it on a flat surface. Do not place the instrument in dirrect sunlight.
Insert the 12 Vdc power plug into its input on the back of the instrument.
Switch on the instrument. On the LCD, the Hanna Logo will appear for a short time, followed by the
main screen for turbidity measurements.
The instrument loads the selected language. If no language can be loaded the instrument will work
in the “safe mode”. In “safe mode” all the messages are displayed in English and
tutorial and help information are not available.
HEATING THE SAMPLE
This procedure can be very effective however it should be handled with care because it can alter the
turbidity of the sample. When heating a sample, the volatile components from the sample can
vaporize, the suspended components can dissolve or the sample characteristics can change.
The heating procedure should be used with extreme care.
Use a warm water bath and immerse the cuvette filled with sample into the bath. Heat the sample
only until the visible bubbles are removed.
Note: Always cool the heated sample to the original temperature before measurement.
The heating procedure can be used in combination with vacuum or ultrasonic waves application for
a more effective air bubble removal.
• Use of an ultrasonic bath;
• Heating the sample.
Sometimes it is necessary to combine two or more methods for efficient air bubble removal.
Note: Each method can alter the sample turbidity, if misused, so they have to be used with caution.
APPLICATION OF VACUUM
Vacuum works by decreasing the atmospheric pressure. The bubbles from the solution come out to
the surface. Application of vacuum is a very simple procedure andany vacuum can be used. The
simplest equipment is a syringe and a rubber stopper.
Notes: • Pay attention that the vacuum equipment be clean and oil-free.
• It is not recommended to apply vacuum to a viscous sample that contains volatile
components. The vacuum can disrupt the volatile components and increase the bubbles
in the sample.
ADDITION OF SURFACTANT
Surfactant changes the surface tension of the water. This causes the bubbles to be released from the
sample. This method is effective for samples that are supersaturated with air.
The procedure consists in the addition of a drop of surfactant in the cuvette before adding the sample
to be analyzed.
A common surfactant used for degassing is Triton X-100.
Warning: Changing the surface tension will cause a rapid settling of particles that cause turbidity.
To avoid this problem, analyze the sample as soon as possible.
Do not shake the sample vigorously because the surfactant may foam. Always rinse the cuvette before
adding a new sample to avoid surfactant accumulation.
Surfactant contribution to the turbidity readings is negligible.
Note: Surfactant addition should be used for degassing only when other methods are ineffective.
USE OF AN ULTRASONIC BATH
The ultrasonic waves are very effective in removing air bubbles from samples. However, ultrasonic
waves should be used with care because they can alter the samples turbidity characteristics, by
modifying the shape and size of particles which cause turbidity. The ultrasonic waves can also break
the existing air bubbles, leading to a complication in the degassing process.
In order to avoid excess application of the ultrasonic waves use the ultrasonic bath until all visible air
bubbles are removed, and then measure the turbidity. This is the most used procedure for degassing.
If you are not sure that all air bubbles were removed, apply ultrasonic waves again for a short period
of time and then measure the turbidity. Repeat this procedure until the turbidity is increasing instead
of decreasing, sign that turbidity of the sample was altered.
In order to degas a sample, fill a clean cuvette with sample and immerse it (1/2 to 2/3 immersed)
in an ultrasonic bath. Follow the degassing procedure described above. Only after the degassing
procedure is finished the cuvette can be capped.