Thermo Scientific 9609BNWP, Руководство пользователя

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20 Fluoride Ion Selective Electrode User Guide
Low-Level Measurements
These procedures are for low ionic strength solutions that do
not contain fl uoride complexing agents and have a fl uoride
concentration of less than 2 x 10
-5
M (0.38 ppm). For solutions
low in fl uoride but high in total ionic strength, perform the same
procedure by preparing a calibrating solution with a composition
similar to the sample. Accurate measurement requires that the
following conditions be met:
• Adequate time must be allowed for electrode
stabilization. Longer response time will be needed at
low-level measurements.
• Stir all standards and samples at a uniform rate.
• Low-level TISAB is recommended for samples and
standards.
Low-Level Setup
1. Prepare the electrode as described in the Electrode
Preparation section.
2. Connect the electrode to the meter. Set the meter to
read mV.
3. Prepare the low-level TISAB. Refer to the Required
Equipment section for instructions. Use low-level TISAB
for low-level measurements only.
4. Prepare 100 mL of standard solution. Dilute the 100 ppm
fl uoride standard, Cat. No. 940907, to 10 ppm or dilute the
0.1 M NaF standard, Cat. No. 940906, to 10
-3
M.
5. Add 100 mL of the low-level TISAB to the 100 mL of
standard.
Low-Level Calibration and Measurement Using a Thermo
Scientifi c Orion ISE Meter with Autoblank Capability
1. When using a Thermo Scientifi c Orion ISE meter in
ISE mode with Autoblank mode enabled, a three point
calibration is usually suffi cient to prepare an accurate
calibration curve at low levels.
2. Choose three calibration points to bracket the
concentrations of interest. It is advised to choose points
which are not more than a factor 10 between each point, for
example, 0.05, 0.5, and 5 mg/L fl uoride standards.