Thermo Fisher Scientific TN100 Turbidimeter - Manual (Page 27)

Instruction Manual TN-100/ T-100
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 Use of an ultrasonic bath: This may be effective in severe conditions or in
viscous samples, but not recommended for ultra-low measurements.
Each of the method above has its own advantages and disadvantages. For instance,
under certain sample conditions, the use of vacuum pump or ultrasonic bath may
actually increase the presence of gas bubbles.
9.4 Timeliness of Sample
Samples should be measured immediately to prevent changes in particle
characteristics due to temperature and settling. Temperature can affect particles by
changing their behavior or creating new particles if precipitates are formed. Dilution
water may dissolve particles or change their characteristics. It is recommended to take
samples only when the turbidimeter is ready to be operated. Samples should not be
drawn and allowed to sit while the instrument warms up or is being readied.
9.5
Other Important Sampling Techniques
1. Samples should not be violently shaken or agitated as particles can be broken
apart or air may be entrapped into the fluid. Gentle agitation such as swirling the
sample vial is advisable to reduce particle settling.
2. Sample vials should be used only with the instruments for which they were
intended. Do not mix and match.
3. Perform a visual observation of the sample vial every time a measurement is made.
Ensure that there are no visible bubbles in the sample and the vial is clean and free
of scratches.
4. Samples entering the turbidimeter should be at the same temperature as the
process flow samples. Changes in temperature can cause precipitation of soluble
compounds and affect readings.
5. Sample vials should be evaluated with a low turbidity water (after cleaning) to
determine if cells remain matched. If the evaluation determines that a cell is
corrupted, discard the vial. It is recommended to conduct this evaluation weekly.
6. When in doubt or question about whether a sample vial is too scratched or stained,
throw it away.
9.6
Calibration
1. Do not open the vials with calibration standards.
2. Check that the standards have not expired.
3. Make sure the calibration vials are free of dust, smudges and scratches before use.
4. Conduct the calibration in the same manner each time. Variations in how calibration
is performed could yield inaccurate measurements.
5. It is very important that the user(s) who perform calibration have been trained to do
so. Creating a Standard Operating Procedure (SOP) for the user(s) to read, learn,
and practice may help to ensure accuracy.
9.7 Dilution
This dilution procedure is necessary only when your turbidity measurement is above
1000 NTU.
1. To measure the turbidity above 1000 NTU, dilute the sample with turbidity-free
water.